2005 Seminars
Time and Date: 10:00 a.m., Wednesday, January 5, 2005
Event: Dept. of Physics & Astronomy Special Talk/Event
Speaker:Guifre Vidal, California Institute of Technology
Subject:``Quantum Information Science and the Efficient Simulation of Quantum ManyBody Systems''
Location:Hennings 318
Time and Date: 2:00 p.m., Wednesday, January 5, 2005
Event: Applied Math/Mathematical Biology Seminar
Speaker:Anmar Khadra, Ph.D. Applied Math/Electrical Engineering, University of Waterloo
Subject:``The Synchronization of ChaosGenerating Systems Using Impulsive Control Techniques
with Applications to Communication Security''
Location:WMAX 216
Time and Date: 2:003:00 p.m., Thursday, January 6, 2005
Event: Complex Fluids Seminar
Speaker:Shreyas Mandre, Department of Mathematics, UBC
Subject:``TBA''
Location:MATX 1118
Time and Date: 3:00 p.m., Thursday, January 6, 2005
Event: DGMPPDE Seminar
Speaker:Qinglan Xia, University of Texas at Austin
Subject:``Ramified phenomena in optimal transportation''
Location:WMAX 216 (PIMS)
Time and Date: 3:00 p.m., Friday, January 7, 2005
Event: Mathematics Colloquium
Speaker:Qinglan Xia, University of Texas at Austin
Subject:
``The Formation of Tree Leaves''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge,
Math Annex (Room 1115).
Time and Date:11:00 a.m., Monday, January 10, 2005
Event: Topology Seminar
Speaker:Krishnan Shankar, University of Oklahoma
Subject:``Dehn functions for finitely presented groups''
Location: WMAX 110 (PIMS facility)
Time and Date:3:00 p.m., Monday, January 10, 2005
Event: IAM Colloquium
Speaker:Neil Balmforth, Earth and Ocean Sciences and Department of Mathematics, UBC
Subject:``Some Geophysical Roll Waves''
Location:Room 301, Leonard S. Klinck Bldg.
Time and Date:4:00 p.m., Monday, January 10, 2005
Event: Mathematics Colloquium
Speaker:Katrin Wherheim, Institute for Advanced Study, Princeton University
Subject:
``Floer Theories in Symplectic Topology and Gauge Theory''
Location: MATH 203
Refreshments will be served at 3:45 p.m. in the Faculty Lounge,
Math Annex (Room 1115).
Time and Date:11:00 a.m., Tuesday, January 11, 2005
Event: DGMPPDE Seminar
Speaker:Katrin Wherheim, Institute for Advanced Study, Princeton University
Subject:``Hofer's scale calculus for moduli spaces''
Location: WMAX 110
Time and Date:2:00 p.m., Wednesday, January 12, 2005
Event: Mathematical Biology Seminar
Speaker:Fred Brauer, Department of Mathematics, UBC
Subject:``The KermackMcKendrick epidemic model revisited''
Location: WMAX 216
Time and Date:3:00 p.m., Wednesday, January 12, 2005
Event: Mathematics Colloquium
Speaker:Frank Sottile, Texas A&M University
Subject:
``Tropical Interpolation''
Location: WMAX 110 (PIMS facility)
Refreshments will be served at the PIMS Facility prior to the colloquium.
Time and Date:2:003:00 p.m., Thursday, January 13, 2005
Event: Complex Fluids Seminar
Speaker:Shreyas Mandre, Department of Mathematics, UBC
Subject:``Energy stability of Couette flow''
Location: MATX 1118
Time and Date:3:00 p.m., Thursday, January 13, 2005
Event: Algebra/Topology Seminar
Speaker:Dylan Thurston, Harvard University
Subject:``A random tunnelnumber one 3manifold does not fiber over the circle''
Location: WMAX 216
Time and Date:4:00 p.m., Thursday, January 13, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Uli Haussmann, Department of Mathematics, UBC
Subject:``A stochastic equilibrium economy with irreversible investment, I''
Location: WMAX 216
Time and Date:3:00 p.m., Friday, January 14, 2005
Event: Mathematics Colloquium
Speaker:Dylan Thurston, Harvard University
Subject:
``How efficiently do 3manifolds bound 4manifolds?''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge,
Math Annex (Room 1115).
Time and Date:3:00 p.m., Monday, January 17, 2005
Event: IAM Colloquium
Speaker:Ozgur Yilmaz, Department of Mathematics, UBC
Subject:
``Blind Separation of Speech Signals via TimeFrequency Masking''
Location: Room 301, Leonard S. Klinck Bldg.
Time and Date:4:00 p.m., Monday, January 17, 2005
Event: Mathematics Colloquium
Speaker:Patrick Brosnan, SUNY at Buffalo
Subject:
``Motives and the algebraic theory of quadratic forms''
Location: MATH 203
Refreshments will be served at 3:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:4:005:00 p.m., Tuesday, January 18, 2005
Event: Algebra/Topology Seminar
Speaker:Patrick Brosnan, SUNY at Buffalo
Subject:``Motivic decompositions arising from the torus method of BialynickiBirula''
Location: MATH 203
Time and Date:2:00 p.m., Wednesday, January 19, 2005
Event: Mathematical Biology Seminar
Speaker:Dan Luciani, Biophysics & Complex Systems Group, Department of Physics, Technical University of Denmark
Subject:``Selfsustained and forced oscillations of cytosolic Ca2+ and glucose metabolism in pancreatic islets''
Location: WMAX 216 (PIMS facility)
Time and Date:4:00 p.m., Wednesday, January 19, 2005
Event: Probability Seminar
Speaker:Nikolai Krylov, University of Minnesota
Subject:``One more square root law for Brownian motion and its application to SPDEs''
Location: WMAX 216
Time and Date:3:004:00 p.m., Thursday, January 20, 2005
Event: DGMPPDE Seminar
Speaker:Yu Yuan, University of Washington
Subject:``A Bernstein problem for special Lagrangian equations''
Location: WMAX 110
Time and Date:4:00 p.m., Thursday, January 20, 2005
Event: PIMSMITACS Math Finance Seminar **CANCELLED**
Speaker:Uli Haussmann, Department of Mathematics, UBC
Subject:``A stochastic equilibrium economy with irreversible investment, II''
Location: WMAX 216
Time and Date:3:00 p.m., Friday, January 21, 2005
Event: Mathematics Colloquium
Speaker:Yu Yuan, University of Washington
Subject:
``Fully Nonlinear Elliptic Equations''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:10:30 a.m., Monday, January 24, 2005
Event: Algebraic Geometry Seminar **Postponed because of visitor's delayed arrival. **
Speaker:Tom Coates, Department of Mathematics, Harvard University
Subject:``Floer homology, quantization, and GromovWitten theory I''
Location:WMAX 110
Time and Date:3:00 p.m., Monday, January 24, 2005
Event: IAMPIMSMITACS Distinguished Colloquium Series
Speaker:Roger Brockett, Electrical Engineering and Computer Science,
Division of Engineering and Applied Sciences, Harvard University
Subject:``Dynamical Systems that do Tricks''
Location:Room 301, Leonard S. Klinck Bldg.
Time and Date:4:00 p.m., Monday, January 24, 2005
Event: Mathematics Colloquium
Speaker:Anders Buch, Aarhus Universitet
Subject:
``Quantum cohomology of Grassmannians''
Location:MATH 203
Refreshments will be served at 3:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:10:00 a.m., Tuesday, January 25, 2005
Event: Algebraic Geometry Seminar
Speaker:Tom Coates, Harvard University
Subject:``Floer homology, quantization, and GromovWitten theory I''
Location:WMAX 110
Time and Date:11:00 a.m., Tuesday, January 25, 2005
Event: DGMPPDE Seminar
Speaker:Michael Goldberg, Department of Mathematics, Caltech
Subject:``A Limiting Absorption Principle in Unweighted L^p Spaces''
Location:WMAX 110
Time and Date:12:302:00 p.m., Tuesday, January 25, 2005
Event: SCAIM Seminar
Speaker:Brett Gladman, Department of Physics and Astronomy, UBC
Subject:``Symplectic integrators applied to largescale dynamical applications in the Solar System''
Location:MATX 1118
Time and Date:4:005:00 p.m., Tuesday, January 25, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Anders Buch, Aarhus Universitet
Subject:``Formulas for quiver varieties''
Location:WMAX 216
Time and Date:10:30 a.m., Wednesday, January 26, 2005
Event: Algebraic Geometry Seminar
Speaker:Tom Coates, Harvard University
Subject:``Floer homology, quantization, and GromovWitten theory II''
Location:WMAX 110
Time and Date:1:302:30 p.m., Wednesday, January 26, 2005
Event: Algebra/Topology Seminar
Speaker:Sunil Chebolu, University of Washington
Subject:``Subcategories and Ktheory for Triangulated Categories''
Location:WMAX 110
Time and Date:3:00 p.m., Wednesday, January 26, 2005
Event: Mathematics Colloquium
Speaker:Michael Goldberg, Department of Mathematics, Caltech
Subject:
``Dispersive Bounds for the Schrodinger Equation with Almost Critical Potentials''
Location:WMAX 110
Refreshments will be served at 2:45 p.m. in WMAX, Room 101, (the PIMS library).
Time and Date:4:00 p.m., Wednesday, January 26, 2005
Event: Probability Seminar
Speaker:Nikolai Krylov, University of Minnesota
Subject:``The Dirichlet problem and diffusion processes in the space of four dimensions more''
Location:WMAX 216
Time and Date:10:00 a.m., Thursday, January 27, 2005
Event: Algebraic Geometry Seminar
Speaker:Tom Coates, Harvard University
Subject:``Floer homology, quantization, and GromovWitten theory III''
Location:WMAX 110
Time and Date:3:004:00 p.m., Thursday, January 27, 2005
Event: DGMPPDE Seminar
Speaker:David Ambrose, Courant Institute, New York University
Subject:``Wellposedness results for water waves and related problems''
Location:WMAX 110
Time and Date:3:003:50 p.m., Thursday, January 27, 2005
Event: Number Theory Seminar
Speaker:Patrick Ingram, UBC
Subject:``Integral points on elliptic curves''
Location:UBC Campus, WMAX 216 (PIMS facility)
First talk will be followed by a tea break (3:504:10 p.m.)
Time and Date:4:104:35 and 4:355:00 p.m., Thursday, January 27, 2005
Event: Number Theory Seminar
Speaker:Peter Borwein, SFU
Subject:``Two problems of Smale that imply a version of P not equal to NP''
and ``A theorem of Duffin and Shaeffer and related stuff"
Location:UBC Campus, WMAX 216
Time and Date:4:00 p.m., Thursday, January 27, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Harjoat Bhamra, UBC Finance
Subject:``The Effect of Financial Innovation on Stock Market Volatility''
Location:WMAX 150
Time and Date:10:30 a.m., Friday, January 28, 2005
Event: Algebraic Geometry Seminar
Speaker:Tom Coates, Department of Mathematics, Harvard University
Subject:``Floer homology, quantization, and GromovWitten theory IV''
Location:WMAX 110
Time and Date:3:00 p.m., Friday, January 28, 2005
Event: Mathematics Colloquium
Speaker:David Ambrose, Courant Institute, New York University
Subject:
``Analysis and computing for freesurface problems in fluid dynamics''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:3:00 p.m., Monday, January 31, 2005
Event: IAM Colloquium
Speaker:Prof. Robert E. O'Malley, Jr., Department of Applied Mathematics, University of Washington
Subject:``Using Amplitude Equations to Solve Initial Value Problems over Long Time Intervals''
Location: Room 301, Leonard S. Klinck Bldg.
Time and Date:4:005:00 p.m., Tuesday, February 1, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Josh Cooper, Courant Institute, New York University
Subject:``Generalized de Bruijn Cycles''
Location: WMAX 216 (PIMS Facility)
Time and Date:10:30 a.m., Wednesday, February 2, 2005
Event: Algebraic Geometry Seminar
Speaker:Mitja Mastnak, Department of Mathematics, UBC
Subject:``About Hopf algebra extensions and cohomologies''
Location: WMAX 110
Time and Date:1:302:30 p.m., Wednesday, February 2, 2005
Event: Algebra/Topology Seminar
Speaker:Nansen Petrosyan, Department of Mathematics, University of WisconsinMadison
Subject:``Groups with periodic cohomology''
Location: WMAX 110
Time and Date:2:00 p.m., Wednesday, February 2, 2005
Event: Mathematical Biology Seminar
Speaker:Jonathan Alberts, UW Biology, and Center for Cell Dynamics, FHL
Subject:``In silico reconstitution of Listeria motility exhibits complex biological behaviors''
Location: WMAX 216
Time and Date:3:00 p.m., Wednesday, February 2, 2005
Event: Mathematics Colloquium
Speaker:Josh Cooper, Courant Institute, New York University
Subject:
``Quasirandom Permutations''
Location: WMAX 110
Refreshments will be served at 2:45 p.m. in WMAX, Room 101, (the PIMS library).
Time and Date:2:003:00 p.m., Thursday, February 3, 2005
Event: Complex Fluids Seminar
Speaker:Anthony Huen, Department of Mechanical Engineering, UBC
Subject:``Stable Multilayer Viscoplastic Shear Flow''
Location: MATX 1118
Time and Date:3:00 p.m., Thursday, February 3, 2005
Event: DGMPPDE Seminar
Speaker:Arpad Benyi, Department of Mathematics & Statistics, University of Massachusetts, Amherst
Subject:``Recent results on bilinear pseudodifferential operators''
Location: WMAX 110
Time and Date:4:00 p.m., Thursday, February 3, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Uli Haussmann, Department of Mathematics, UBC
Subject:``A stochastic equilibrium economy with irreversible investment, II''
Location: WMAX 216
Time and Date:3:00 p.m., Friday, February 4, 2005
Event: Mathematics Colloquium
Speaker:Arpad Benyi, Department of Mathematics & Statistics, University of Massachusetts, Amherst
Subject:
``From linear to bilinear pseudodifferential operators''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:3:00 p.m., Monday, February 7, 2005
Event: IAM Colloquium
Speaker:Michael Friedlander, Department of Computer Science, UBC
Subject:``Solving Quadratic Programs via Gradient Projection''
Location: Room 301, Leonard S. Klinck Bldg.
Time and Date:4:00 p.m., Monday, February 7, 2005
Event: Mathematics Colloquium
Speaker:Joseph Maher, California Institute of Technology
Subject:
``Geometries and covers of 3manifolds''
Location: MATH 203
Refreshments will be served at 3:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:12:302:00 p.m., Tuesday, February 8, 2005
Event: SCAIM Seminar
Speaker:Sarah Mitchell, Department of Mathematics, UBC
Subject:``An Asymptotic Framework for Finite Hydraulic Fractures driven by Multiple Physical Processes''
Location: MATX 1118
Time and Date:4:005:00 p.m., Tuesday, February 8, 2005
Event: Algebra/Topology Seminar
Speaker:Joseph Maher, California Institute of Technology
Subject:``Heegaard splittings and virtual fibers''
Location: West Mall Annex 110 (WMAX  PIMS Facility)
Time and Date:4:005:00 p.m., Tuesday, February 8, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Dimitris Achlioptas, Microsoft Corporation, Redmond, WA
Subject:``Phase Transitions in Hard Optimization Problems''
Location: WMAX 216 (PIMS Facility)
Time and Date:10:30 a.m., Wednesday, February 9, 2005
Event: Algebraic Geometry Seminar
Speaker:Angelo Vistoli, Bologna
Subject:``Chow rings of classifying spaces for classical groups''
Location: WMAX 110
Time and Date:3:004:00 p.m., Wednesday, February 9, 2005
Event: Joint ProbabilityMathematical Biology Seminar ** Please note special time and location. **
Speaker:Babak Pourbohloul, BC Center for Disease Control
Subject:``Control of Respiratoryborne disease outbreaks in populations: A Contact Network Theory Approach''
Location: WMAX 110
Time and Date:4:005:00 p.m., Wednesday, February 9, 2005
Event: Mathematics Colloquium
Speaker:Dimitris Achlioptas, Microsoft Research
Subject:
``Applications of Random Matrices in Spectral Computations and Machine Learning''
Location: WEST MALL ANNEX (WMAX) 110
Refreshments will be served at 3:45 p.m. in WMAX, Room 101 (the PIMS library).
Time and Date:10:00 a.m., Thursday, February 10, 2005
Event: Algebraic Geometry Seminar
Speaker:Megumi Harada, Department of Mathematics, University of Toronto
Subject:``Computation of generalized equivariant cohomologies of KacMoody flag varieties''
Location: WMAX 110
Time and Date:2:003:00 p.m., Thursday, February 10, 2005
Event: Complex Fluids Seminar
Speaker:Pramond Patil, Department of Chemical & Biological Engineering, UBC
Subject:``PTFE Paste Extrusion: Modeling using a Structural Parameter''
Location: MATX 1118
Time and Date:3:003:50 p.m., Thursday, February 10, 2005
Event: Number Theory Seminar
Speaker:Ron Ferguson, PIMS
Subject:``The merit factor problem for binary sequences''
Location: SFU Campus, Room K9509
First talk will be followed by a tea break (3:504:10 p.m.)
Time and Date:4:105:00 p.m., Thursday, February 10, 2005
Event: Number Theory Seminar
Speaker:Nike Vatsal, Department of Mathematics, UBC
Subject:``Elliptic curves and modular forms''
Location: SFU Campus, Room K9509
Time and Date:4:00 p.m., Thursday, February 10, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Abel Cadenillas, Dept. of Mathematical & Statistical Sciences, University of Alberta
Subject:``Classical and impulse control for the optimization of the risk and dividend policy of a financial corporation''
Location: WMAX 216
Time and Date:4:00 p.m., Thursday, February 17, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Ronnie Sircar, ORFE Department, Princeton University
Subject:
``Valuation of Employee Stock Options''
Location: WMAX 216
Time and Date:3:00 p.m., Monday, February 21, 2005
Event: IAM Seminar
Speaker:Mark Martinez, Department of Chemical and Biological Engineering, UBC
Subject:``An Introduction into the Mathematics of Papermaking''
Location: Room 301, Leonard S. Klinck Bldg.
Time and Date:11:00 a.m., Tuesday, February 22, 2005
Event: DGMPPDE Seminar
Speaker:Evar Ekeland, PIMS, UBC
Subject:``Regularity in an unusual variational problem''
Location: WMAX 110 (PIMS Facility)
Time and Date:12:302:00 p.m., Tuesday, February 22, 2005
Event: SCAIM Seminar
Speaker:Ian Mitchell, Computer Science, UBC
Subject:``A Toolbox of HamiltonJacobi Solvers for Analysis of Nondeterministic Continuous and Hybrid Systems,
and for Dynamic Implicit Surfaces''
Location: FSC 1611 (south side of Forestry Bldg. main floor)
Time and Date:4:005:00 p.m., Tuesday, February 22, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Malek Abdesselam, Department of Mathematics, UBC
Subject:``Feynman diagrams, classical invariant theory, resultants, and the HadamardFoulkesHowe conjecture''
Location: WMAX 216
Time and Date:10:30 a.m., Wednesday, February 23, 2005
Event: Algebraic Geometry Seminar
Speaker:Julianna Tymoczko, U. of Michigan, Ann Arbor
Subject:``Generalizing group exponents using the topology of subvarieties of the flag variety''
Location: WMAX 110
Time and Date:1:302:30 p.m., Wednesday, February 23, 2005
Event: Algebra/Topology Seminar
Speaker:Jeffrey H. Smith, Purdue University
Subject:``The homotopy theory of the Alperin conjecture''
Location: WMAX 110
Time and Date:2:00 p.m., Wednesday, February 23, 2005
Event: Mathematical Biology Seminar
Speaker:Colin Clark, Professor Emeritus, Department of Mathematics, UBC
Subject:``A potpourri of Fishy Models''
Location: WMAX 216
Time and Date:3:00 p.m., Wednesday, February 23, 2005
Event: Mathematics Colloquium
Speaker:Sergei Krutelevich, Department of Mathematics & Statistics, University of Ottawa
Subject:
``Jordan algebras, exceptional groups, and higher composition laws''
Location: WMAX 110 (PIMS Facility)
Refreshments will be served at 2:45 p.m. in WMAX, Room 101, (the PIMS library).
Time and Date:4:15 p.m. (Pls note special time.), Wednesday, February 23, 2005
Event: Probability Seminar
Speaker:AlainSol Sznitman, ETH Zurich
Subject:``On random walks in random environment''
Location: WMAX 216
Time and Date:2:00 p.m. (Pls note special time.), Thursday, February 24, 2005
Event: Joint Complex FluidsSCAIM Seminar
Speaker:Guido Kanschat, Applied Mathematics, U. Heidelberg
Subject:``Discontinuous Galerkin Methods for Incompressible Flow''
Location: MATX 1118
Time and Date:4:00 p.m., Thursday, February 24, 2005
Event: Algebra Seminar
Speaker:Sergei Krutelevich, University of Ottawa
Subject:``The Freudenthal construction and orbits of exceptional groups''
Location: WMAX 216
Time and Date:4:00 p.m., Thursday, February 24, 2005
Event: Graduate Student Seminar
Speaker:Yinan Song, Department of Mathematics, UBC
Subject:``GromovWitten/DonaldsonThomas correspondence''
Location: MATX 1102
Time and Date:4:00 p.m., Thursday, February 24, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Anthony Ware, Department of Mathematics, University of Calgary
Subject:``Natural gas option pricing under meanreverting price models''
Location: WMAX 110 (Please note the exceptional location.)
Time and Date:3:00 p.m., Friday, February 25, 2005
Event: Mathematics Colloquium
Speaker:Jeffrey H. Smith, Purdue University
Subject:
``A Tour of the Homotopy Category''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:3:00 p.m., Monday, February 28, 2005
Event: IAM Seminar
Speaker:Robert Bridson, Department of Computer Science, UBC
Subject:``Animating Fluids''
Location:Room 301, Leonard S. Klinck Bldg.
Time and Date:4:005:00 p.m., Tuesday, March 1, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Richard Anstee, Department of Mathematics, UBC
Subject:``Some new and interesting results in matching theory''
Location:WMAX 216
Time and Date:1:302:30 p.m., Wednesday, March 2, 2005
Event: Algebra/Topology Seminar
Speaker:Alejandro Adem, PIMS, UBC
Subject:``Toroidal Orbifolds and Group Cohomology''
Location:WMAX 110
Time and Date:3:30 p.m., Wednesday, March 2, 2005
Event: Probability Seminar
Speaker:AlainSol Sznitman, ETH Zurich
Subject:``Invariance principle and isotropic diffusions in random environment''
Location:WMAX 216
Time and Date:2:003:00 p.m., Thursday, March 3, 2005
Event: Complex Fluids Seminar
Speaker:Juha Salmela, Pulp and Paper Center, UBC
Subject:``Floc Rupture and ReFlocculation in Turbulent Shear Flow''
Location:MATX 1118
Event: 3:003:50 p.m., Thursday, March 3, 2005
Time and Date:Number Theory Seminar
Speaker:Brian Conrad, University of Michigan
Subject:``Irreducible specialization in characteristic 2''
Location:UBC Campus, WMAX 110 (PIMS Facility)
Time and Date:4:00 p.m., Thursday, March 3, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Alexander Melnikov, Department of Mathematics, U. of Alberta
Subject:``Quantile Hedging and Valuation of equitylinked life insurance contracts''
Location:WMAX 216
Time and Date:3:00 p.m., Friday, March 4, 2005
Event: Mathematics Colloquium
Speaker:AlainSol Sznitman, ETH Zurich
Subject:
``Random motions in random media''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:3:30 p.m., Friday, March 4, 2005
Event: SCAIM Seminar
Speaker:James Burke, Department of Mathematics, U. of Washington
Subject:``The Blondel Belgian Chocolate Prize for Polynomial Stabilization:
Insights from Nonsmooth Optimization''
Location:UBC Robson Square, Room C225
Time and Date:3:004:00 p.m., Monday, March 7, 2005
Event: IAMPIMSMITACS Distinguished Colloquium Series
Speaker:Adrian Nachman, Department of Mathematics and
Department of Electrical & Computer Engineering, U of Toronto
Subject:``Inverse Problems in Medical Imaging''
Location: Room 301, Leonard S. Klinck Bldg.
Time and Date:11:00 a.m., Tuesday, March 8, 2005
Event: DGMPPDE Seminar
Speaker:Xiaodong Yan, Michigan State University
Subject:``An example in 2D nonlinear elasticity''
Location: West Mall Annex 110 (PIMS Facility)
Time and Date:3:30 p.m., Tuesday, March 8, 2005
Event: DGMPPDE Seminar
Speaker:Fengbo Han, Michigan State University
Subject:``The Sobolev inequality for Paneitz operator on Berger spheres''
Location: WMAX 110
Time and Date:4:005:00 p.m., Tuesday, March 8, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Matthew Morin, UBC
Subject:``The chormatic symmetric function of caterpillars''
Location: WMAX 216
Time and Date:10:30 a.m., Wednesday, March 9, 2005
Event: Algebraic Geometry Seminar
Speaker:Nils Bruin, SFU
Subject:``The arithmetic of Prym varieties in genus 3
(with applications to finding the rational points on curves)''
Location: WMAX 110
Time and Date:2:00 p.m., Wednesday, March 9, 2005
Event: Mathematical Biology Seminar
Speaker:Artem Cherkasov, Division of Infectious Diseases, Faculty of Medicine, UBC
Subject:``Reliability and network analysis in genomics''
Location: WMAX 216
Time and Date:3:30 p.m., Wednesday, March 9, 2005
Event: Probability Seminar
Speaker:Richard Bass, Department of Mathematics, U of Connecticut
Subject:``Renormalized selfintersection local time and the range of random walks''
Location: WMAX 216
Time and Date:4:00 p.m., Thursday, March 10, 2005
Event: Graduate Student Seminar
Speaker:Mathew Rogers, Department of Mathematics, UBC
Subject:``Bessel functions and infinite series''
Location: MATX 1102
Time and Date:4:00 p.m., Thursday, March 10, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Sebastian Ferrando, Ryerson University
Subject:``Martingales and Wavelets: Applications to Hedging Financial Derivatives''
Location: WMAX 216
Time and Date:3:00 p.m., Friday, March 11, 2005
Event: Mathematics Colloquium
Speaker:Richard Bass, University of Connecticut
Subject:
``Jump processes: some links with analysis and PDE''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).
Time and Date:1:002:30 p.m., Monday, March 14, 2005
Event: UBC Department of Linguistics sponsored Seminar
Speaker:Chungchieh Shan, Department of Computer Science, Harvard University
Subject:``Linguistic side effects''
Location: The Buchanan Penthouse, BUCH B 500 (Access is via the SE 4th Flr. Landing.)
Time and Date:3:004:00 p.m., Monday, March 14, 2005
Event: IAM Seminar
Speaker:Anthony Peirce, Department of Mathematics, UBC
Subject:``Hydraulic Fracture: Multiscale Processes and Moving Interfaces''
Location:Room 301, Leonard S. Klinck Bldg.
Time and Date:11:00 a.m., Tuesday, March 15, 2005
Event: DGMPPDE Seminar
Speaker:Michael Lacey, Georgia Tech
Subject:``Commutators in Several Parameters''
Location:West Mall Annex 110 (PIMS Facility)
Time and Date:11:30 a.m., Tuesday, March 15, 2005
Event: Computer Science Seminar
Speaker:Chungchieh Shan, Department of Computer Science, Harvard University
Subject:``Meanings are programs with side effects''
Location: FSC 1003 (Forest Sciences Centre)
Time and Date:12:30 p.m., Tuesday, March 15, 2005
Event: SCAIM Seminar
Speaker:David Watkins, Mathematics, Washington State University
Subject:``Product Eigenvalue Problems''
Location:FSC 1611
Time and Date:4:005:00 p.m., Tuesday, March 15, 2005
Event: Problems in Discrete Maths Seminar
Speaker:Shlomo Hoory, Computer Science, UBC
Subject:``Simple permutations mix well''
Location:WMAX 216
Time and Date:10:30 a.m., Wednesday, March 16, 2005
Event: Algebraic Geometry Seminar
Speaker:Kevin Purbhoo, Department of Mathematics, UBC
Subject:``A Nullstellensatz for Amoebas''
Location:WMAX 110
Time and Date:1:302:30 p.m., Wednesday, March 16, 2005
Event: Algebra/Topology Seminar
Speaker:Johann Leida, University of Wisconsin
Subject:``Homotopy Theory of Orbifolds I''
Location:WMAX 110
Time and Date:2:00 p.m., Wednesday, March 16, 2005
Event: Mathematical Biology Seminar
Speaker:Jens Rademacher, Department of Mathematics, UBC
Subject:``Global bifurcations, spectra and dynamics of travelling waves''
Location:WMAX 216
Time and Date:3:30 p.m., Wednesday, March 16, 2005
Event: Probability Seminar Postponed 1 week til March 23rd.
Speaker:Alex Roitershtein, Department of Mathematics, UBC
Subject:``On multitype branching processes with immigration in random environment''
Location:WMAX 216
Time and Date:2:003:00 p.m., Thursday, March 17, 2005
Event: Complex Fluids Seminar
Speaker:Markus Weiler, Departments of Forest Resources Management and Geography, UBC
Subject:``Blue water in macropores''
Location:MATX 1118
Time and Date:3:00 p.m., Thursday, March 17, 2005
Event: DGMPPDE Seminar
Speaker:Louis Nirenberg, NYU
Subject:``A geometric problem and its connection to the Hopf lemma''
Location:WMAX 110
Time and Date:3:003:50 p.m., Thursday, March 17, 2005
Event: Number Theory Seminar
Speaker:Michael Rubinstein, University of Waterloo
Subject:``Elliptic curves and random matrix theory''
Location:SFU Campus, Room K9509
Tea break: 3:50  4:10 p.m.
Time and Date:4:105:00 p.m., Thursday, March 17, 2005
Event: Number Theory Seminar
Speaker:Chandrashekhar Khare, University of Utah
Subject:``Serre's conjectures on mod p Galois representations''
Location:SFU Campus, Room K9509
Time and Date:4:00 p.m., Thursday, March 17, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Ivar Ekeland, PIMS, UBC
Subject:``On Bond Prices''
Location:WMAX 216
Time and Date:3:00 p.m., Friday, March 18, 2005
Event: Mathematics Colloquium
Speaker:Sara Billey, University of Washington
Subject:
``Intersecting Schubert Varieties''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. in the Faculty Lounge,
Math Annex (Room 1115).
Time and Date:11:00 a.m., Tuesday,
March 29, 2005
Event: DGMPPDE Seminar
Speaker: Jerome Demange, Toulouse
Subject:``Porous Media Equation and Sobolev
Inequalities on Manifolds''
Location: West Mall Annex (WMAX) 110 (PIMS Facility)
Time and Date:4:005:00 p.m., Tuesday, March 29, 2005
Event: Problems in Discrete Maths Seminar
Speaker: Roger Woodford
Subject:``Prime Symmetric Divisor Functions''
Location: WMAX 216
Time and Date:10:30 a.m., Wednesday, March 30, 2005
Event: Algebraic Geometry Seminar
Speaker: Mike Roth, Queen's
Subject:``Stable Maps and Quot Schemes''
Location: WMAX 110
Time and Date: 1:30
p.m., Wednesday, March 30, 2005
(Please note 1/2 hr earlier than usual)
Event: Mathematical Biology Seminar
Speaker: Gustavo Carrero, Department of Mathematics,
University of Alberta
Subject:``Modelling the Compartmentalization of
Splicing Factors''
Location: WMAX 216
Time and Date:3:004:00 p.m., Wednesday, March 30,
2005
Event: IAMPIMSMITACS Distinguished
Colloquium Series
Speaker: Raymond Pierrehumbert, Department of
Geophysical Sciences, University of Chicago
Subject:``EarlyLife Crises of Habitable Planets''
Location: Room 301, Leonard S. Klinck Bldg.
Time and Date:3:30 p.m., Wednesday, March 30, 2005
Event: Probability Seminar
Speaker: John Walsh, Department of Mathematics, UBC
Subject:``Some Remarks on the Numerics of the
Nonlinear Stochastic Wave Equation''
Location: WMAX 216
Time and Date: 1:00 p.m., Thursday, March 31, 2005
Event: Special Probability Seminar
Speaker: Jeremy Flowers
Subject:``Hydrodynamical Scaling Limits of Simple
Exclusion Processes''
Location: MATX 1118
Time and Date: 4:00 p.m., Thursday, March 31, 2005
Event: Graduate Student Seminar
Speaker: Izak Grguric, Department of Mathematics, UBC
Subject:``Equivariant Cobordism''
Location: MATX 1102
Time and Date: 4:00
p.m., Thursday, March 31, 2005
Event: PIMSMITACS Math Finance
Seminar
Speaker: Ulrich Horst,
Department of Mathematics, UBC
Subject: "NonErgodic Stock Price Dynamics in a
CAPM with Interacting Agents"
Location: WMAX 216
Time and Date:3:00 p.m., Monday, April 4, 2005
Event: Special Probability Seminar
Speaker:Jeremy Flowers, Department of Mathematics, UBC
Subject:``Hydrodynamical Scaling Limits of Simple Exclusion Processes II''
Location: MATX 1102
Time and Date:11:00 a.m., Tuesday, April 5, 2005
Event: DGMPPDE Seminar
Speaker:TaiPeng Tsai, Department of Mathematics, UBC
Subject:``Stability in H^1 of the sum of K solitary waves for some nonlinear Schrodinger equations''
Location: WMAX 110
Time and Date:12:30 p.m., Tuesday, April 5, 2005
Event: SCAIM Seminar
Speaker:Pengtao Yue & Chunfeng Zhou, Chemical & Biological Engineering, UBC
Subject:``A FiniteElement DiffuseInterface Method for Interfacial Flows with Adaptive Meshing''
Location: MATX 1118
Time and Date:2:00 p.m., Wednesday, April 6, 2005
Event: Mathematical Biology Seminar
Speaker:Adriana Dawes, Department of Mathematics, UBC
Subject:``Modelling the spatial profile of barbed ends and filament density behind the leading edge of a motile cell''
Location: WMAX 216
Time and Date:3:00 p.m., Wednesday, April 6, 2005
Event: Algebraic Geometry Seminar
Speaker:Alexander Yong, Berkeley
Subject:``On Smoothness and Gorensteinness of Schubert varieties''
Location: WMAX 110
Time and Date:3:30 p.m., Wednesday, April 6, 2005
Event: Probability Seminar
Speaker:Ulrich Horst, Department of Mathematics, UBC
Subject:``State dependent queuing systems with semiMarkov switching and applications to finance''
Location: WMAX 216
Time and Date:2:00 p.m., Wednesday, April 13, 2005
Event: Mathematical Biology Seminar
Speaker:Christopher Kribs Zaleta, U. Texas, Arlington
Subject:``Vector consumption and contact process saturation in sylvatic transmission of T. cruzi''
Location:WMAX 216
Time and Date:3:00 p.m., Friday, April 15, 2005
Event: Mathematics Colloquium
Speaker:Boris Kunyavskii, Bar Ilan University
Subject:
``Characterization of radicals in finite dimensional Lie algebras and finite groups''
Location:WMAX 110 (PIMS Facility)
Refreshments will be served at 2:45 p.m. in the PIMS 1st floor lounge.
Time and Date:1:30 p.m., Monday, April 18, 2005
Event: Algebra Topology Seminar
Speaker:Hendryk Pfeiffer, Cambridge University
Subject:``From Hopf algebras to trialgebras and Hopf categories''
Location: WMAX 110
Time and Date:3:00 p.m., Monday, April 18, 2005
Event: Mathematics Colloquium
Speaker:R. Sujatha, School of Mathematics, Tata Institute of Fundamental Research
Subject:
``Birational Geometry and localisation''
Location: WMAX 110 (PIMS Facility)
Refreshments will be served at 2:45 p.m. in the PIMS 1st floor lounge.
Time and Date:2:00 p.m., Wednesday, April 20, 2005
Event: Mathematical Biology Seminar
Speaker:Don Ludwig, Emeritus, Department of Mathematics, UBC
Subject:``Uncertainty in Discount Models and Mitigation of Environmental Change''
Location: WMAX 216
Time and Date:3:00 p.m., Tuesday, April 26, 2005
Event: Algebraic Geometry Seminar
Speaker:Behrang Noohi, MaxPlanck Institute
Subject:``Uniformization of DeligneMumford curves''
Location:WMAX 110
Time and Date:2:00 p.m., Wednesday, April 27, 2005
Event: Mathematical Biology Seminar
Speaker:Amil Shah, MDCM, FRCPC, FACP Medical Oncologist, Vancouver Cancer Centre
Subject:``In Search of the Achilles Heel of Cancer''
Location:WMAX 216
Time and Date:3:00 p.m., Friday, April 29, 2005
Event: Mathematics Colloquium
Speaker:Benny Sudakov, Princeton University
Subject:
``Probabilistic reasoning and Ramsey Theory''
Location:WMAX 110 (PIMS Facility)
Refreshments will be served at 2:45 p.m. in the PIMS 1st floor lounge.
Time and Date:9:00 a.m. 6:00 p.m., Friday, June 3, 2005
Event: Foundational Methods in Computer Science (FMCS05)
Local organizer: John MacDonald
Location:All sessions are held in WMAX 110  1933 West Mall.
9:0010:30a.m. Ernie Manes, U Mass Amherst, USA
Subject:``From locallyBoolean rings to sumordered categories''
11:0012:30p.m. Vaughan Pratt, Stanford University, USA
Subject:``Recent developments in Chu spaces''
2:304:00p.m. Steve Bloom, Stevens Institute of Technology, USA
Subject:``Regular words''
4:306:00p.m. Robin Cockett, University of Calgary
Subject:``Restriction Categories and Ehresmann's Theorem''
Time and Date:9:00 a.m. 5:00 p.m., Saturday, June 4, 2005
Event: Foundational Methods in Computer Science (FMCS05)
9:009:50a.m. Paul Taylor, Manchester, UK
Subject:``Extension of ASD (from locally compact locales) to and beyond general locales''
9:5010:30a.m. Cyrus Nourani, USA
Subject:``Functorial Model Computations''
11:0011:30a.m TBA
11:3012:15p.m. Art Stone, Vancouver, Canada
Subject:``2Dimensional Adjunctions''
2:002:30p.m. Varmo Vene, University of Tartu, Estonia
Subject:``Signals and Comonads''
2:303:00p.m. Bob Rosebrugh, Mt. Allison University
Subject:``TBA''
3:003:30p.m. Chris Dutchyn, University of British Columbia
Subject:``Aspects are Dual to Objects''
4:005:00p.m. Philip Mulry, Colgate University, USA
Subject:``Monad Compositions on Recursive Data Types''
Time and Date:9:00 a.m. 12:30 p.m., Sunday, June 5, 2005
Event: Foundational Methods in Computer Science (FMCS05)
9:009:30a.m. Brian Redmond, University of Ottawa
Subject:``Categorical Models for Soft Linear Logic''
9:3010:00a.m. X. Guo, University of Calgary
Subject:``Range Restriction Categories''
10:0010:30a.m. Dana Harrington, University of Calgary
Subject:``TBA''
10:3011:00a.m. Break
11:0011:30a.m. David Oury, McGill University
Subject:``TBA''
11:3012:00p.m. Pieter Hofstra, University of Ottawa
Subject:``TBA''
12:0012:30p.m. TBA
Last updated: 5/27/05
Time and Date: 4:005:00 p.m., Thursday, June 16, 2005
Event: Probability Seminar
Speaker:Thomas Duquesne, ENS, Paris
Subject:``Brownian and Levy Continuum Random Trees''
Location:West Mall Annex 110 (Coffee will be served at 3:30 p.m. in the 1st floor PIMS Lounge.)
Time and Date: 3:30  4:30 p.m., Wednesday, August 31, 2005
Event: Probability Seminar
Speaker: Stanislav Volkov, U. Bristol, UK
Subject:``5x+1: how many go down?''
Location: West Mall Annex Room 216, 1933 West Mall, PIMS Facility
Abstract: I will talk about how probabilistic methods
of analyzing
randomlylabeled trees can provide an important insight
on the 5x+1 version of the famous
Collatz problem (3x+1), you might have a
look at
http://mathworld.wolfram.com/CollatzProblem.html (Mathworld).
Though no
rigorous results about number theory will be proved in my talk, a number of
properties of the trees with random labels will be rigorously established.
Time and Date:11:00 a.m., Wednesday, September 7, 2005
Event: Algebraic Geometry Seminar
Subject:Organizational Meeting
Location:West Mall Annex, Room 110, 1933 West Mall, PIMS
Time and Date:2:00 p.m., Wednesday, September 7, 2005
Event: Mathematical Biology Seminar
Speaker:Lindi Wahl, U of Western Ontario
Subject:``Modelling Experimental Evolution''
Location:West Mall Annex, Room 216, 1933 West Mall, PIMS
Abstract: In experimental evolution, populations of microbes
are grown under laboratory conditions for thousands of generations 
enough time for significant evolutionary change to occur. The results of
these experiments in the past several years have shed enormous light on
the trajectories and outcomes of evolution. In parallel with this experimental
effort, we have developed mathematical models of experimental evolution,
deriving in particular the probability that rare, beneficial mutations will
emerge and invade the population. I will give an overview of our techniques
and results to date, highlighting some interesting predictions of the model.
For example, we derive an optimal dilution ratio, that is, the length of time
populations should be allowed to grow in order to maximize the rate of
evolution. In addition, we predict that mutations which allow the microbe to
reproduce more quickly, as opposed to reproducing more prolifically, are less
likely to invade.
Time and Date:3:304:30 p.m., Wednesday, September 7, 2005
Event: Probability Seminar
Speaker:Gord Slade, Department of Mathematics, UBC
Subject:``The survival probability for critical oriented percolation above 4+1 dimensions''
Location:West Mall Annex, Room 216
Abstract: We consider spreadout critical oriented
percolation in d + 1 dimensions. We develop a new pointtoplane version of
the lace expansion and use it to prove that the probability that
the cluster of the origin survives to time n is asymptotic to a
multiple of n^{1}, when d is greater than 4. This is joint work
with Remco van der Hofstad and Frank den Hollander.
Time and Date:3:304:20 p.m., Thursday, September 8, 2005
Event: DGMPPDE Seminar
Speaker:Tetsu Mizumachi, Kyushu University
Subject:``Instability of vortex solitons for 2D focusing NLS''
Location:West Mall Annex, Room 110
Abstract: We consider standing wave solutions
e^{i(m\theta+\omega t)}\phi_{\omega,m}(r) to
iu_t+\Delta u+u^{p1}u=0,\quad\text{for x\in\R^2, t>0,}
where m\in\N and (r,\theta) are polar coordinates in \R^2. We investigate a
limiting profile of \phi_{\omega,m} as m\to\infty and show that for every
p>1 the standing wave solutions are unstable for large m.
Time and Date:4:005:00 p.m., Thursday, September 8, 2005
Event: Math Finance Seminar
Speaker:Matthias Mueller, Department of Mathematics, UBC
Subject:``Pricing and hedging market external risks: weather and climate''
Location:West Mall Annex, Room 216
Abstract: Weather and climate risks can not be hedged on
stock markets. Those risk factors are market external. The utility indifference
pricing approach does not give satisfying results because the market is
too incomplete. Our approach is the completion of the market by a risk bond.
This risk bond makes the external risk tradable. In presence of an exogenously
given stock market, a fixed point argument yields the price for the external
risk factor. If the preferences of the economic agents are described by
exponential utility, the market price of external risk is defined by a
Backward Stochastic Differential Equation. In Markovian models, this BSDE
can be transformed into a quasilinear PDE. Simulations of toy models give
some insight in prices and hedging strategies.
Time and Date:3:00 p.m., Friday, September 9, 2005
Event: Mathematics Colloquium
Speaker:Mike Bennett, Department of Mathematics, UBC
Subject:
``Diophantine Equations, Old and New''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Faculty Lounge).
Time and Date:2:003:00 p.m., Monday, September 12, 2005
Event: Algebra Topology Seminar
Speaker:Antonio Ramirez, Department of Mathematics, UBC
Subject:``String Topology''
Location:West Mall Annex, Room 216 (PIMS)
Note: We will have a short organizational meeting before the talk.
Anyone who is interested in the seminar but cannot make this meeting
should send Laura Scull an email.
Time and Date:3:00 p.m., Monday, September 12, 2005
Event: IAM Seminar Series
Speaker:Michael Doebeli, Zoology, Mathematics, IAM, UBC
Subject:``The Steacie Fellowship Prize Lecture: Evolution and Diversity''
Location:Room 301, Leonard S. Klinck Bldg.
Abstract: Understanding the origin of diversity
is a fundamental problem in biology. Traditional evolutionary theory predicts
uniformity: acting on organisms under given environmental conditions and
developmental constraints, natural selection produces a unique, optimally
adapted phenotype. According to this view, different types only come about
through a change in conditions over space or time. In particular, the process
of diversification, that is, the split of an ancestral population into distinct
descendent lineages, is a byproduct of geographical separation. This traditional
view misses out on the important perspective that diversification itself can
be an adaptive process. In this talk I will review recent theoretical work
showing that diversification as an adaptive response to biological interactions
is a plausible evolutionary process. This work is based on the mathematical
framework of adaptive dynamics, and in particular on the phenomenon of evolutionary
branching due to frequencydependent ecological interactions. I will describe
evolutionary branching in a number of different models, including models for
competitive and for cooperative interactions. I will also describe ongoing efforts
to test the theory of evolutionary branching in evolving Escherichia coli populations,
which provide a promising experimental model system for studying adaptive diversification.
Time and Date:3:004:00 p.m., Monday, September 12, 2005
Event: Algebraic Geometry Seminar
Speaker:Jim Bryan, UBC
Subject:``HurwitzHodge integrals and the Crepant Resolution Conjecture''
Location:West Mall Annex, Room 110 (PIMS)
Abstract: A well known principle from physics states that string theory
on an orbifold X is equivalent to string theory on Y, any crepant resolution of X.
In mathematics, this can be stated as saying that the GromovWitten potentials
for X and Y contain equivalent information. I will illustrate this in some simple
examples and show how it leads to interesting new formulas for integrals of Hodge
classes over Hurwitz schemes.
Time and Date:12:30 p.m., Tuesday, September 13, 2005
Event: SCAIM Seminar
Speaker:Ping Lin, Department of Mathematics, National University of Singapore
Subject:``A quasicontinuum approximation for material problems and its analysis''
Location:Math Annex 1118
Abstract: In many applications materials are modeled by a large number of
particles (or atoms) where any one of particles interacting with all
others through a (nonconvex) pair potential energy. The equillibrium
configuration of the material is the minimizer of the total energy of
the system. The computational cost is very high since the number of
atoms is huge. Recently much attention has been paid to a socalled
quasicontinuum (QC) method which is a mixed atomistic/continuum model.
The QC method solves a fully atomistic problem in regions where the
material contains defects (or larger deformation gradients), but uses
continuum finite elements to effectively integrate out the majority
of the atomistic degrees of freedom in regions where deformation
gradients are small. However, numerical analysis is still at its
infancy. In this talk we will conduct a convengence analysis of the
QC method in the case that there is no defect or that the defect
region is small. The difference of our analysis from conventional one
is that our exact solution is not a solution of a continuous partial
diffeeential equation but a discrete lattice scale solution which is
not related to any conventional partial differential equation. We
will consider both one dimensional and two dimensional cases. The
talk may be related to some other fields such as model reduction and
preconditioning.
Pizza and pop served, as usual.
Time and Date:3:304:30 p.m., Tuesday, September 13, 2005
Event: Joint SFU/UBC Discrete Math/CS Theory Seminar
Speaker:Gabor Tardos, Simon Fraser University
Subject:``Toward an Extremal Theory of Ordered Graphs''
Location:West Mall Annex, Room 216 (PIMS at UBC)
Abstract: Pattern avoidance raises very interesting extremal enumerative and
structural problems in many different contexts from Turantype
extremal graph theory to DavenportSchinzel theory. This survey
talk concentrates to 01 matrices and (the closely related concepts of)
ordered graphs. An ordered graph is simple graph together with a
linear order on its vertices.
Time and Date:2:453:35 p.m., Wednesday, September 14, 2005
Event: PIMS Afternoon Tea
Location:West Mall Annex, Room 101 (PIMS Library)
Time and Date:3:304:30 p.m., Wednesday, September 14, 2005
Event: Probability Seminar
Speaker:Alan Hammond, Department of Mathematics, UBC
Subject:``Massconservation and gelation in reactiondiffusion PDE''
Location:West Mall Annex, Room 216
Abstract: Smoluchowski's coagulation equation is a PDE that models the changing
densities of a system of mass bearing particles that diffuse and are
liable to coagulate in pairs at close range.
We analyse the behaviour of solutions of the PDE by monitoring the
trajectory of a tracer particle, this particle diffusing in space and
colliding with other particles in accordance with the densities provided
by a given solution of the PDE.
We prove uniform bounds on the total particle density under certain
assumptions on the parameters that specify the PDE. These permit us to
derive conditions under which the solutions conserve mass for all time.
In the other case, a gelation phenomenon occurs, much like a phase
transition. Time permitting, I will also discuss results proving that
gelation occurs.
Time and Date:4:005:00 p.m., Thursday, September 15, 2005
Event: Math Finance Seminar
Speaker:Matthias Mueller, Department of Mathematics, UBC
Subject:``Pricing and hedging market external risks:
weather and climate  Open Problems''
Location:West Mall Annex, Room 216
Time and Date:4:005:30 p.m., Thursday, September 15, 2005
Event:Complex Fluids Seminar
Speaker:Pramod D. Patil, Department of Chemical and Biological Engineering, UBC
Subject:``Microstructural modeling and flow simulations of PTFE paste extrusion''
Location:MATH 225
Abstract: Because of its high melt viscosity, polytetrafluoroethylene (PTFE)
is usually processed by paste extrusion instead of conventional melt processing
techniques. Experimentally it has been reported that the extrusion pressure varies
nonmonotonically with the entrance angle of the conical die attached at the bottom
of a capillary extruder. SEM micrographs show the formation of submicrondiameter
fibrils in between polymer particles due apparently to squeezing of neighboring
particles inside the converging conical die and unwinding of mechanically locked
crystallites. In the present study the mechanism of fibrillation is captured
through a microscopic model for a structural parameter that accounts for the
population of fibrils. The evolution of the structural parameter is described
by a firstorder kinetic differential equation. A constitutive equation is
constructed that shows shearthinning and shearthickening behavior depending
on the evolution of the structural parameter during extrusion. Finite element
simulations have predicted variations of the extrusion pressure with the apparent
shear rate and die geometry, especially the die entrance angle. The simulation
results will be compared with experimental findings.
Key words: PTFE paste, extrusion, conical die, fibrils, microstructural parameter,
shear thinning, Shear thickening, finite element simulations
Time and Date:3:00 p.m., Friday, September 16, 2005
Event: Mathematics Colloquium
Speaker:Alexander Holroyd, Department of Mathematics, UBC
Subject:
``The Bootstrap Percolation Cellular Automaton 
a case study in Theory versus Experiment''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Faculty Lounge).
Time and Date:3:004:00 p.m., Monday, September 19, 2005
Event: IAM Seminar Series
Speaker:Michael Ward, Department of Mathematics, UBC
Subject:``The Stability of Stripes, Rings, and Spots, in some ReactionDiffusion Systems''
Location:Room 301, Leonard S. Klinck Bldg.
Abstract: Stripe or ring patterns have been observed in many numerical
simulations of singularly perturbed reactiondiffusion systems. They
occur for activatorinhibitor systems such as the wellknown
GiererMeinhardt model of biological morphogenesis, for certain hybrid
chemotaxis reactiondiffusion systems modeling fish skin patterns on
growing domains, and for the GrayScott
system of theoretical chemistry. In many instances a stripe or ring
pattern is unstable to a breakup instability, which leads to the
disintegration of the stripe or ring into a sequence of spots. In
other cases, a stripe is destabilized by a transverse or zigzag
instability, leading to a wriggled stripe. In certain cases, this
wriggled stripe is the precursor to a complicated spacefilling
labyrinthian pattern. Most previous studies of this phenomenon are
based on a weakly nonlinear theory near some spatially uniform
steadystate. In contrast, the stripes that we consider are typically
localized along some planar curves and have crosssections that
deviate substantially from the background state. The crosssections
are either homoclinic or frontback transition solutions of certain
ODE systems. Our analysis of stripe stability involves a combination
of singular perturbation theory, the spectral theory of nonlocal
eigenvalue problems, and numerical computations. The instabilities of
these localized stripes are illustrated for various reactiondiffusion
models, and some general results are given for the occurrence of
spotgenerating instabilities, zigzag instabilities, and labyrinthian
patterns.
This is joint work with Theodore Kolokolnikov, Wentao Sun, and Juncheng Wei.
Time and Date:3:004:00 p.m., Monday, September 19, 2005
Event: Algebraic Geometry Seminar
Speaker:HsianHua Tseng, Department of Mathematics, UBC
Subject:``Bend and break: old and notsoold''
Location:West Mall Annex, Room 110 (PIMS)
Abstract:"Bend and break" was introduced by S. Mori as a way to produce
rational curves on smooth projective varieties. The method was further
developed by J. Kollar for singular varieties. In this talk we'll review
this technique for smooth varieties. We'll then discuss a different approach
to extend it to singular varieties (joint work with JiunCheng Chen).
Time and Date:12:30 p.m., Tuesday, September 20, 2005
Event: SCAIM Seminar
Speaker:Chen Greif, Department of Computer Science, UBC
Subject:``Preconditioners for the TimeHarmonic Maxwell Equations in Mixed Form''
(joint work with Dominik Schoetzau, UBC)
Location:Math Annex 1118
Abstract:We introduce a new preconditioning technique for iteratively
solving linear systems arising from finite element discretizations of
the mixed formulation of the timeharmonic Maxwell equations, with small
wave numbers. The preconditioners are based on augmentation, and are
motivated by spectral equivalence properties of the discrete operators.
We show that using the scalar Laplacian as a weight matrix
works as an effective block diagonal preconditioner, for which fast
iterative solution methods can be applied. The analytical
observations are accompanied by numerical examples that demonstrate
the scalability of the technique.
Time and Date:3:30 p.m., Tuesday, September 20, 2005
Event: DGMPPDE Seminar
Speaker:Stephen Gustafson, Department of Mathematics, UBC
Subject:``Scattering for the GrossPitaevskii equation''
Location:West Mall Annex, Room 110 (PIMS)
Abstract: The GrossPitaevskii equation, a model for BoseEinstein
condensates, superfluids, and superconductors, is just a familiar
nonlinear Schroedinger equation, but with a nonzero limit at
spatial infinity. This boundary condition makes it a more challenging
(and interesting) problem to determine the longtime behaviour of
solutions. I'll give some nonlinear scattering background, and
describe some results (joint with K. Nakanishi and T.P. Tsai)
and open problems.
Time and Date:3:304:30 p.m., Tuesday, September 20, 2005
Event: Discrete Math Seminar
Speaker:Chris Ryan, Commerce, UBC
Subject:``Coincidences amongst products of Schur functions''
Location:West Mall Annex, Room 216 (PIMS)
Time and Date:2:00 p.m., Wednesday, September 21, 2005
Event: Mathematical Biology Seminar
Speaker:Steven Plotkin, Physics and Astronomy, UBC
Subject:``How does a protein fold? The effects of structure,
and a segue into differential geometry''
Location:West Mall Annex, Room 216
Abstract:The elusive theory for how a protein folds up to a
biologically functional structure has occupied researchers
for the last few decades. The difficulties stem from an incomplete
knowledge of an accurate Hamiltonian, as well as nontrivial
aspects of polymer physics that complicate the kinetics of folding.
Here I will describe some recent results showing that relaxation
rates increase significantly as the folding mechanism becomes
increasingly heterogeneous. A search for a suitable reaction
coordinate leads to an unsolved problem in differential geometry,
namely a precise mathematical formulation of distance between
objects of dimension > 0. A distance metric for two noncrossing
space curves can be formulated as a variational problem, mapping
to the solution of a partial differential equation. I will describe
these developments and discuss some possible future directions.
Time and Date:2:453.35 p.m., Wednesday, September 21, 2005
Event: PIMS Tea
Location:West Mall Annex, Room 101 (PIMS Library)
Time and Date:3:30 p.m., Wednesday, September 21, 2005
Event: Algebra Topology Seminar
Speaker:Antonio Ramirez, Department of Mathematics, UBC
Subject:``OpenClosed String Topology''
Location:West Mall Annex, Room 110
Abstract: This is a continuation to last week's
talk on string topology. I will continue with TQFT aspects of string
topology, and describe how the constructions can be extended to the
"open closed" setting, in which one considers not only loops but also
spaces of paths in M with endpoint conditions given by submanifolds.
The method of construction is homotopy theoretic, and it makes use of
constrained mapping spaces from certain decorated fat graphs into the
ground manifold M.
Time and Date:3:304:30 p.m., Wednesday, September 21, 2005
Event: Probability Seminar
Speaker:David Wilson, Microsoft Research
Subject:``Randomturn games''
Location:West Mall Annex, Room 216
Abstract: The game of Hex has two players who take
turns placing stones of their colors on the hexagons of a rhombusshaped
hexagonal grid. Black wins by completing a crossing between two opposite edges,
while White wins by completing a crossing between the other pair of opposite edges.
Although ordinary Hex is famously difficult to analyze, randomturn
Hexin which players toss a coin before each turn to decide who gets
to place the next stonehas a simple optimal strategy. We describe
the optimal strategy and study the expected length of the game under
optimal play for randomturn Hex and several other ``selection games''.
We also study another class of randomturn games, called tugofwar,
which is played on a length space X with terminal states at which
there is a payoff; the winner of the coin toss may move the current
state by up to distance epsilon. Strategies for tugofwar give a new
way to study the infinityLaplacian.
Joint work with Yuval Peres, Oded Schramm, and Scott Sheffield.
Time and Date:4:005:00 p.m., Thursday, September 22, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker:Dmity Kramkov, Carnegie Mellon University
Subject:``On the twotimes differentiability of the value functions
in the problem of optimal investment in incomplete markets''
Location:West Mall Annex, Room 216
Abstract:We study the twotimes differentiability of the value functions
to the primal and dual optimization problems that appear in the setting
of expected utility maximization in incomplete markets. We also
study the differentiability of the optimal solutions to these
problems with respect to their initial values. We show that the key
conditions for the results to hold true are that the relative
riskaversion coefficient of the utility function is uniformly
bounded away from zero and infinity and that the prices of traded
securities are sigmabounded under the numeraire given by the
optimal wealth process.
The presentation is based on a joint paper with Mihai Sirbu. The preprint
is available from http://www.math.cmu.edu/~kramkov/publications.html .
Time and Date:4:005:30 p.m., Thursday, September 22, 2005
Event: Complex Fluids Seminar
Speaker:Paul X. Chen, Dept. of Chemical and Biological Engineering, UBC
Subject:``Drop/Interface Coalescence in NonNewtonian Liquid''
Location:MATH 225
Abstract: When a water drop falls through oil and comes to rest on an
oilwater interface, several interesting phenomena may occur. First, the
oil film separating the drop and the water bath underneath is squeezed
and gets thinner. The drainage of the film depends on the viscosity
of the oil, among other things, and its efficiency, represented by a
rest time, varies greatly among different fluids. Second, the coalescence
between the drop and the water bath may be arrested before completion
if a capillary instability in the neck develops faster than the deflation
of the drop. A smaller secondary drop pinches off from the neck and will
remain on the interface. This episode, known as partial coalescence,
repeats itself several times before the drop finally disappears. In
this talk, I will describe experiments designed to explore the role of
oil rheology in the above phenomena. In particular, I will present data
on rest time, coalescence time, and the reduction of drop size during
partial coalescence when polymer is added to the oil phase. Video footage
captured with our newly acquired highspeed camera will reveal details
of the process. Some of the results are unexpected and unexplained
at present.
Time and Date:3:00 p.m., Friday, September 23, 2005
Event: Mathematics Colloquium
Speaker:Rachel Kuske, Department of Mathematics, UBC
Subject:
``Hidden time scales and stochastic dynamics''
Location:MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 2:45 p.m., Monday, September 26, 2005
Event: Mathematics Departmental Tea
Location: Math Annex 1115 (Math Lounge)
Time and Date: 3:004:00 p.m., Monday, September 26, 2005
Event: IAMPIMSMITACS 20052006 Distinguished Colloquium Series
Speaker: Eli Tziperman, Department of Earth and Planetary Sciences,
Division of Engineering and Applied Sciences, Harvard University
Subject:``Rapid Past Climate Change: It's the Sea Ice''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: Heinrich events are massive glacier discharges from the ice sheets
around the North Atlantic Ocean which occurred every 7,00010,000 years during
the last glacial period (10,00050,000 years ago). Each of these events also
triggered an abrupt atmospheric warming of some 10 degrees Celsius around the
northern North Atlantic. The warming (DansgaardOeschger event) occurred
rapidly, in about twenty years, lasted a few hundred years, and terminated
abruptly again, within a few decades. We suggest that such past rapid climate
changes during the last glacial maximum have occurred due to rapid sea ice
melting and formation. A specific mechanism is proposed for the climatic effects
of Heinrich events. The synchronous iceberg discharges from several ice sheets
around the North Atlantic are explained by a nonlinear phase locking between
the different glaciers.
Time and Date: 3:004:00 p.m., Monday, September 26, 2005
Event: Algebraic Geometry Seminar
Speaker: Michael Thaddeus, Columbia U., PIMS
Subject:``Stable maps to loop groups''
Location: West Mall Annex, Room 110 (PIMS)
Time and Date: 12:30 p.m., Tuesday, September 27, 2005
Event: SCAIM Seminar
Speaker: Ofer Levi, Department of Industrial Engineering and Management,
BenGurion University of the Negev, Israel
Subject:``Direct and Exact Inverse PPFFT and Radon Transforms
Using Orthogonalizing Weights''
Location: Math Annex 1118
Abstract: The PseudoPolar FFT (PPFFT), which was developed and
presented by Averbuch et. al, computes Discrete Fourier Transform
coefficients on a nearly polar grid. The special structural properties
of the PseudoPolar grid allow a computational complexity of o(n2log(n))
for an n by n image (as opposed to o(n4) in the polar case).
Averbuch et. al. also presented a weighted version of the PPFFT
that is nearly orthogonal and can be used for the application of an
extremely fast iterative inverse solver. The PPFFT is directly
related to a highly accurate and fast version of the Discrete Radon
Transform that possesses the same desirable computational
properties as the PPFFT, the Fast SlantStack Transform.
In many instances and applications the PPFFT can be a very good
substitute for the Polar FT and its superior computational
properties can speed up many related algorithms by several orders
of magnitude. Classical applications of Polar FFT include
rotational registration of images and reconstruction in medical and
biological imaging.
The preliminary part of this talk will introduce the basics of 2D
DFTs in Cartesian, Polar and PP grids using matrices and vectors
notation. Later on, a new direct an exact inverse PPFFT will be
presented, the algorithm is based on a preprocessing step in which
an optimal set of weights is computed for the given image size,
these weights perfectly orthogonalize the columns of the
transform's matrix so the inverse problem can be solved exactly by
a single application of the Adjoint PPFFT which can be computed as
well in o(n2log(n)) complexity. The results will be generalized to
3D as well as to radon transforms in 2D and 3D.
Time and Date: 3:30 p.m., Tuesday, September 27, 2005
Event: DGMPPDE Seminar
Speaker: Hadi Jorati, Department of Mathematics, UBC
Subject:``Singular kernels adapted to curved flags''
Location: West Mall Annex, Room 110
Abstract: The classical theory of CalderonZugmund kernels in
\mathbb{R}^n exploits the study of distributions that are almost
invariant under the class of isotropic dilations. In this talk we
consider convolution operators with distributions that behave
simply under a specified class of nonisotropic dilations in the plane.
The prototypical example being the operator of Hilbert transform along
the parabola in \mathbb{R}^2.
Using machinery of flag kernels and multipliers, developed by Nagel,
Ricci, Stein, we describe the form of the multiplier for such operators,
and, as a corollary, prove their L^p boundedness for 1
Time and Date: 3:304:20 p.m., Tuesday, September 27, 2005
Event: Joint SFU/UBC Discrete Math Seminar at SFU
Speaker: Richard Anstee, UBC
Subject:``Forbidden Configurations: An update''
Location: SFU Campus, Applied Science Building 10908 (IRMACS Seminar Room)
Abstract: Forbidden configurations are a kind of forbidden induced 'pattern'
in matrices (for those who attended Gabor Tardos' lecture). We say
a (0,1)matrix is simple if it has no repeated columns. Let F be
a k x l (0,1)matrix. We say that a simple matrix A has no
Fconfiguration if no submatrix of A is a row and column permutation
of F. We are interested in the extremal function forb(m,F) which is
the maximum number of columns in an mrowed simple matrix that has
no Fconfiguration. A conjecture of Sali and A. predicts the assymptotic
behaviour of forb(m,F) for fixed F as m tends to infinity. With Keevash,
we develop a stability result for kuniform tintersecting set systems
that determines forb(m,F) for F being k x 2. With Fleming, Furedi and Sali,
we have a linear algebra argument for all but `one' k x l F where forb(m,F)
is O(m^{k1}). This is joint work with Peter Keevash, Balin Fleming,
Zoltan Furedi, and Attila Sali.
Time and Date: 2:00 p.m., Wednesday, September 28, 2005
Event: Mathematical Biology Seminar
Speaker: Rodrigo A. Restrepo (Emeritus), Department of Mathematics, UBC
Subject:``A Plausible Ancestry for the tRNAs''
Location: West Mall Annex, Room 216 (PIMS)
Abstract: After examining the frequent occurrences of some RNA
segments in 657 prokaryotic gene sequences, this work suggests
that the development of the tRNAs began with two small RNA segments,
specified here, formed in abundant numbers early in the history of
the Earth. These segments may have grown larger and diversified
in the manner suggested here, becoming able to interact with some
specific amino acids before the emergence of the genetic code.
These suggestions are supported here by many statistical tests
on the tRNAs of prokaryotes.
Time and Date: 2:453:35 p.m., Wednesday, September 28, 2005
Event: PIMS Tea
Location:West Mall Annex, Room 101 (PIMS Library)
Time and Date: 3:304:30 p.m., Wednesday, September 28, 2005
Event: Probability Seminar
Speaker: Nathanael Berestycki, Department of Mathematics, UBC
Subject:``Of mice and men (and random walks)''
Location: West Mall Annex, Room 216
Abstract: We study of genome rearrangements, which have the following
flavor: given two species (say, mice and men), can we estimate their
divergence time, i.e. the time elapsed since their most recent common
ancestor? On a mathematical level, this leads to study a striking phase
transition for the behavior of the distance of a certain random walk
on the symmetric group called the random transposition random walk.
Crucially, this problem involves a connection with ErdosRenyi random
graphs and may be formulated in terms of coalescence and fragmentation.
Motivated by related biological questions we also study the limiting
behavior for the distance of other random walks and try to identify
those for which there is a similar phase transition. These examples
include random adjacent transpositions, random pcycles, and a random
walk on a random 3regular graph.
Time and Date: 4:00 p.m., Wednesday, September 28, 2005 (refreshments start at 3:30 p.m.)
Event: IAM StudentFaculty Seminar
Speaker: Alexei Cheviakov, Postdoctoral Fellow, Department of Mathematics, UBC
Subject:``Modelling the Equilibrium States of Plasmas: PDE Properties, Exact Solutions and Physical Models"
Location: LSK 301 (refreshments in LSK 306)
Abstract: I will start with a review of some physical
phenomena and applications involving plasmas, and present the corresponding
model PDEs. We will concentrate on the continuum isotropic model of plasmas
 the system of Magnetohydrodynamics (MHD) equations. It is a fully nonlinear
3D system. Its equilibrium version is known for its very special solution
topology. I will discuss necessary physical properties of equilibrium solutions,
overview the known methods of construction of exact solutions, and present
several families of exact solutions with relevant physical models.
One of possible ways of construction of new exact solutions to a PDE system
is symmetries  maps of the solution manifold into itself. I will show how
the rich symmetry structure of equilibrium MHD equations significantly
extends and diversifies the set of known exact solutions (and corresponding
physical models).
Differences, similarities and relations of MHD with NavierStokes and Euler
models will be outlined.
Time and Date: 12:30 p.m., Thursday, September 29, 2005
Event: Mathematics Colloquium
Speaker: JeongYup Lee, Department of Mathematics, University of Victoria
Subject:
``Pure point diffractive, coincidence,and cutandproject set in substitution point sets (tilings)''
Location: MATH 203
Time and Date: 3:003:50 p.m., Thursday, September 29, 2005
Event: SFU/UBC Number Theory Seminar
Speaker: Chris Sinclair, PIMS, SFU, UBC
Subject:``Counting reciprocal polynomials with integer coefficients''
Location: West Mall Annex, Room 110
Abstract: I'll introduce a method which will allow us to produce asymptotic
estimates for the number of reciprocal polynomials with integer coefficients,
bounded degree and bounded Mahler measure. This method can be extended to other
multiplicative measures of complexity of polynomials. Time permitting, I will
demonstrate a connection between these topics and physics.
Time and Date: 4:005:00 p.m., Thursday, September 29, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker: Robert Elliot, Haskayne School of Business, University of Calgary
Subject:``Indifference Pricing and Real Options''
Location: West Mall Annex, Room 216
Abstract: The field of real options is based on the simple
observation that in many projects, or contracts, there are
implicit options. Most of the work on pricing such options is
very suspect and often is nothing more than an application of
techniques from equity pricing. However, the underlying assets in
real options are usually not tradeable which invalidates many of
the results.
In a paper to appear in a Princeton University Press volume,
edited by Rene Carmona, Elliott and van der Hoek have developed a
theory of indifference pricing for non tradeable assets which
bridges the risk neutral pricing of complete markets and certainty
equivalence as used by actuaries.
The talk will outline these ideas and show how they can be applied
to pricing real options.
Time and Date: 4:005:30 p.m., Thursday, September 29, 2005
Event: Complex Fluids Seminar
Speaker: Boris Stoeber, Department of Mechanical Engineering, UBC
Subject:``Viscothermal instabilities in microchannels and a novel
micromixing concept based on thermally responsive polymer solutions''
Location: MATH 225
Abstract: Microfluidics, the fluid dynamics on a very small length scale,
is a rapidly growing field being driven by new technological applications
in the life sciences, materials and chemical sciences. Biotechnology
for example has a demand for highthroughput lowcost bioanalysis and
synthesis systems for diagnostics and research purposes. Because of
the typically small length scales of microfluidic components, the
effects driving and dominating fluid motion in microfluidic systems
are substantially different from effects in largescale systems. This
requires the development of new flow control strategies for the
management of very small liquid volumes.
In a novel microflow control strategy poloxamers, heat sensitive
polymers, are introduced into the fluid samples. These polymer
solutions gel reversibly at elevated temperatures. At ambient
temperatures close to the phase transition viscous heating within the
fluid can lead to flow unsteadiness. It can cause gel formation along
the channel walls either in a periodic manner or until the entire
channel is pinched off. When the solution temperature of pressure
driven flow is slightly higher than the gel temperature, the Pluronic
solution will behave as a highly viscous nonNewtonian liquid. Flow
velocity fluctuations develop at increased temperatures. In this flow
regime flow instabilities might result from the competing mechanisms
of shearthinning and thermothickening of the solution.
Rapid heating of these polymer solutions from below the gel
temperature to far above results in fast gelation of the material.
This effect can be used to build a fast microfluidic valve with
integrated electric heaters in a microchannel because heat transfer
occurs rapidly across the small channel dimension. Local heating of
the fluid results in gel formation and subsequent channel blockage
within less than 33 ms. A novel laminar mixing concept employs such
active valves that are placed in specific locations in a microchannel
system. Cyclic actuation of these valves results in periodic flow
redirection in the channel system leading to substantial stretching
and folding of the fluid layers. Mixing occurs rapidly and effectively
through diffusion across the resulting thin layers.
Time and Date: 4:105:00 p.m., Thursday, September 29, 2005
Event: SFU/UBC Number Theory Seminar
Speaker: Michael Bennett, UBC
Subject:``Integer points on congruent number curves''
Location: West Mall Annex, Room 110
Abstract: An integer N is called a congruent number if there exists a
rightangled triangle with area N, all three of whose sides have rational
lengths. Equivalently, N is a congruent number if the elliptic curve
y^2 = x^3  N^2*x has positive MordellWeil rank over the rational numbers.
In this talk, we consider the question of finding integer points on these
elliptic curves and discuss a number of related issues.
Time and Date: 3:00 p.m., Friday, September 30, 2005
Event: Mathematics Colloquium
Speaker: Vlada Limic, Department of Mathematics, UBC
Subject:
``Lambdacoalescent processes and genealogies''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 4:00 p.m., Friday, September 30, 2005
Event: Specialized Seminar
Speaker: JeongYup Lee, Department of Mathematics, University of Victoria
Subject: ``Pure point diffractive substitution point sets are Meyer sets''
Location: MATH 103
Abstract: We say that a point set is a Meyer set if the point set is
relatively dense (there is no arbitrary big hole in the space without a
point of the point set) and the set of all translations in the point set
is uniformly discrete (has minimum separation between elements). The
importance of Meyer sets in the theory of longrange aperiodic order has
been revealed in many investigations. We show that a substitution point
set, which is pure point diffractive, is a Meyer set, and observe that any
Meyer substitution point set with an expansion map has a property that
eigenvalues of the expansion map form a Pisot family, that is to say,
the set of eigenvalues of the expansion map consists of all conjugates of
eigenvalues of the map whose modulus larger than or equal to 1.
Time and Date: 3:004:00 p.m., Monday, October 3, 2005
Event: IAM 20052006 Seminar Series
Speaker: J.F. Williams, Assistant Professor, Department of Mathematics, SFU
Subject:``Adaptive Strategies for the Numerical Simulation of PDEs with FiniteTime Singularities''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: Many mathematical models of real world phenomena take the form
of partial differential equations which may exhibit singularities in
finite time. In this talk, I shall discuss adaptive strategies in both
space and time for the resolution of such behaviour. This adaptive approach
is based on scaling properties of the PDE, which leads to uniform error
estimates, rather than on information about particular solutions. Examples
in one and two dimensions from a variety of applications will be presented.
This is joint work with C. J. Budd (University of Bath).
Time and Date: 3:004:00 p.m., Monday, October 3, 2005
Event: Algebraic Geometry Seminar
Speaker: Michael Thaddeus, Columbia U., PIMS
Subject:``Stable maps to loop groups, II''
Location: WMAX Room 110 (PIMS)
Time and Date: 4:00 p.m., Monday, October 3, 2005
Event: Mathematics Colloquium
Speaker: Julia Gordon, Department of Mathematics, University of Toronto
Subject:
``Motivic measure and padic groups''
Location: MATH 104
Note: The Mathematics Tea will be served at 3:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 2:00 p.m., Tuesday, October 4, 2005
Event: Algebraic Geometry Seminar
Speaker:Julia Gordon, University of Toronto
Subject:``Are characters of padic groups computable?''
Location: WMAX Room 110
Abstract: It is known that in general, it is impossible to have
a formula for characters of representations of padic groups,
because there are examples of the character values that depend
on a number of points of elliptic or hyperelliptic curves over
finite fields. However, one can ask if the equations for varieties
that are responsible for character values can be found explicitly
(and if such varieties exist in general). This talk will address
these questions (under certain circumstances both answers are positive).
We will use the group SL(2, Q_p) as a source of explicit examples for
"motivic" calculations.
Time and Date: 3:30 p.m., Tuesday, October 4, 2005
Event: DGMPPDE Seminar
Speaker: Pierpaolo Esposito, Department of Mathematics, UBC
Subject:``A singularly perturbed Neumann/Dirichlet problem:
pointwise concentration towards spikelayer solutions''
Location: WMAX Room 110
Abstract: KellerSegel and GiererMeinhardt proposed a mathematical
model to describe the evolution of two substances interacting with
different diffusion rates. It leads to a system of two coupled nonlinear
parabolic equations. The study of stationary solutions for this problem
can be reduced, under some assumption on the diffusion rates, to the study
of a singularly perturbed Neumann equation with polynomial nonlinearity.
We will give an overview of known results concerning this equation and
present some new result in order to outline the strong differences between
the case of subcritical and critical nonlinearity, between the concentration
phenomena on finitely many points and on higherdimensional sets. We will
also discuss this equation under Dirichlet boundary condition.
Time and Date: 3:304:30 p.m., Tuesday, October 4, 2005
Event: Discrete Math Seminar
Speaker: Laura Dunwoody, UBC
Subject:``Problems of forbidden configurations''
Location: WMAX Room 216 (PIMS)
Time and Date: 2:00 p.m., Wednesday, October 5, 2005
Event: Mathematical Biology Seminar
Speaker: Eric Cytrynbaum, Department of Mathematics, UBC
Subject:``Finding the center  how to solve simple geometry problems at the cellular scale''
Location: WMAX Room 216
Abstract: Fragments of fish melanophore cells can form and center aggregates
of pigment granules by dyneinmotordriven transport along a selforganized
radial array of microtubules (MTs). I will present a quantitative model that
describes pigment aggregation and MTaster selforganization and the subsequent
centering of both structures. The model is based on the observations that MTs
are immobile and treadmill, while dyneinmotorcovered granules have the ability
to nucleate MTs. From assumptions based on experimental observations, I'll
derive partial integrodifferential equations describing the coupled granuleMT
interaction. Scaling arguments and perturbation theory allow for analysis
in two limiting cases. This analysis explains the mechanism of aster self
organization as a positive feedback loop between motor aggregation at the
MT minus ends and MT nucleation by motors. Furthermore, the centering mechanism
is explained as a global geometric bias in the cell established by selfnucleated
microtubules. Numerical simulations lend additional supports to the analysis.
The model sheds light on role of polymer dynamics and polymermotor interactions
in cytoskeletal organization.
Time and Date:2:453.35 p.m., Wednesday, October 5, 2005
Event: PIMS Tea
Location:WMAX Room 101 (PIMS Library)
Time and Date: 3:30 p.m., Wednesday, October 5, 2005
Event: Algebra Topology Seminar
Speaker: Steve Smith, University of Illinois at Chicago
Subject:``Homotopy decompositions and classifying spaces for sporadic simple groups''
Location: WMAX Room 110
Abstract: In the case of simple groups, it can be advantageous to seek a
decomposition with further properties not necessarily possessed by the usual
decompositionfor example, one with minimum possible dimension for
computational purposes. A longterm project with Dave Benson has achieved
this goal for the 26 sporadic simple groups. The talk will indicate some
of the history and background; leading up to some of the intriguing similarities
in the behavior of these very different groups.
Time and Date: 3:304:30 p.m., Wednesday, October 5, 2005
Event: Probability Seminar
Speaker: David Brydges, Department of Mathematics, UBC
Subject:``Joint density for the local times of continuoustime random walks''
Location: WMAX Room 216
Abstract: We investigate the local times of continuoustime random walks
on arbitrary discrete state spaces. For fixed finite range of the random
walk, we derive an explicit formula for the joint density of all local
times on the range, at any fixed time. We apply this formula in the
following directions
(1) We prove the analog of the wellknown RayKnight description of
Brownian local times for continuoustime simple random walk on \Z,
(2) we derive large deviation estimates for exponential integrals of
the normalized local times beyond the exponential scale.
Time and Date: 4:00 p.m., Wednesday, October 5, 2005
Event: IAM StudentFaculty Seminar
Speaker: Nataliya Ivanova, Department of Mathematics, UBC
Subject:``Symmetries of Differential Equations''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: In this lecture we will give a notion of symmetry (invariance)
transformation of differential equations and consider different types
of symmetries. A constructive algorithmic way of finding Lie symmetries
will be presented. We will consider several applications of symmetries
to solving differential equations.
Time and Date: 4:005:00 p.m., Thursday, October 6, 2005
Event: Graduate Student Seminar
Speaker: Warren Code, Department of Mathematics, UBC
Subject:``SturmLiouville problems with boundary conditions that depend on the eigenparameter''
Location: MATX 1102
Time and Date: 4:005:30 p.m., Thursday, October 6, 2005
Event: Complex Fluids Seminar
Speaker: Speaker: Chunfeng Zhou, Department of Chemical & Biological Engineering, UBC
Authors: Chunfeng Zhou, Pengtao Yue and James J. Feng
Subject:``A computational study of drop formation in microfluidic devices''
Location: MATH 225
Abstract: Capillarity has a prominent role in flow in microfluidic devices
because of the typically small linear dimensions, large curvature and large
surface area in these geometries. Applications of microdrops and microbubbles
in small channels range from micropumps to ultrasound contrast agents [1].
In this study, we concentrate on the process of drop formation in microdevices,
which has been used for generating uniform emulsions of Newtonian and nonNewtonian
fluids, with an emphasis on the effects of fluid rheology. The bulk rheology and
interfacial motion are described in a phasefield framework [2], and the numerical
solution uses a finiteelement algorithm with adpative meshing to ensure proper
resolution of the interfaces. We will present simulations of drop formation at
the tip of a jet inside a flowfocusing device as demonstrated in recent experiments [1,3].
The rheology of the components may be Newtonian, viscoelastic with the OldroydB models being used for the latter. Results show
that component rheology is a major determinant in the morphology of the jet, the
details of the breakup process, and the size distribution of drops. The solutions
compare favorably with experiments.
Time and Date: 3:00 p.m., Friday, October 7, 2005
Event: Mathematics Colloquium
Speaker: Steve Smith, University of Illinois at Chicago
Subject:
``Quasithin groups and the classification of the finite simple groups''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 12:30 p.m., Tuesday, October 11, 2005
Event: SCAIM Seminar
Speaker: Challa S. Sastry, Department of Earth and Ocean Sciences, UBC
Subject:``Multiresolution Methods and Applications''
Location: CS X736 (7th floor of the new CS Bldg.) PLEASE NOTE THIS LOCATION.
Abstract: The multiresolution algorithms, provided by the wavelets, enable us
to divide a complicated function into several simpler ones and study
them separately. This property along with their localization
property makes them very attractive in the implementations of
analysis and synthesis problems that arise in different real life
applications. The presentation aims at discussing the multiresolution
algorithms along with some of their applications to information
retrieval from image databases, image reconstruction in tomography etc.
Time and Date: 3:304:30 p.m., Tuesday, October 11, 2005
Event: SFU/UBC Discrete Mathematics Seminar
Speaker: Bojan Mohar, SFU
Subject:``Quadrangulations, Eulerian triangulations and 5critical graphs''
Location: SFU, IRMACS Centre, ASB 10900 (www.irmacs.ca)
Abstract: Quadrangulations of the projective plane (and of other
nonorientable surfaces) have interesting properties in relation
to graph colorings. Some of them will be uncovered in this talk
and applied to the study of colorings of locally 3colorable triangulations.
Time and Date: 3:30 p.m., Tuesday, October 11, 2005
Event: DGMPPDE Seminar
Speaker: Zhiqin Lu, UC Irvine
Subject:``WeilPetersson geometry on CalabiYau moduli''
Location: WMAX 110 (PIMS Seminar Room)
Abstract: In this talk, we study the differential geometry
of the CY moduli. We prove the following results on the CY moduli:
first, the integrations of the Chern classes of the WeilPetersson
metric are rational numbers, second, we give a condition on the
incompleness of the WeilPetersson metric when the dimension of the
moduli space is greater than 1. This work is joint with Michael
Douglas and Eisuke Natsukawa.
Time and Date: 4:30 p.m., Tuesday, October 11, 2005
Event: DGMPPDE Seminar
Speaker: Massimiliano Berti, Department of Mathematics & Statistics, McMaster University
Subject:``Nonlinear oscillations in Hamiltonian PDEs''
Location: WMAX 110 (PIMS)
Abstract: The classical problem of finding periodic and quasiperiodic
solutions of nonlinear Hamiltonian PDEs has substantially progressed
by a new interplay between variational methods, dynamical systems
techniques and NashMoser implicit function theorems. We present new
recent existence results for both free and forced vibration problems
in nonlinear wave equations, where both infinite dimensional
bifurcation problems and small divisors difficulties arise.
Time and Date: 2:00 p.m., Wednesday, October 12, 2005
Event: Mathematical Biology Seminar
Speaker: Nicola Fameli, Department of Physics & Astronomy, UBC
Subject:``Modeling of Ca2+ transport in smooth muscle cells''
Location: WMAX 216 (PIMS)
Abstract: I will present a stochastic numerical model simulating the
transport of calcium ions (Ca 2+) within the junctional spaces between
the plasma membrane and the sarcoplasmic reticulum of smooth muscle cells.
In this type of cells, release of Ca 2+ from the sarcoplasmic reticulum (SR)
is thought to be responsible for contractile activation. In this scenario,
measurements of [Ca 2+] oscillations suggest that to replenish the
sarcoplasmic reticulum and maintain contraction, Ca 2+ from the extracellular
space are taken up by the sarcoplasmic reticulum having traversed the buffer
spaces between the plasma membrane (PM) and the SR. These spaces are known as
junctions. The model assumes the propagation of Ca 2+ occurs by diffusion
through the junctional cytosol between the PM and the SR. The typical path
of Ca 2+ diffusing inside the junctional space is therefore simulated as
a three dimensional random walk from ion sources to ion sinks, representing
the ion transporters Na +/Ca2+ exchanger and SERCA pumps, respectively.
Results of this study in conjunction with [Ca 2+], force transduction and
electron microscopy measurements seem to reinforce the idea that Ca 2+
uptake via PMSR junctions is a possible and plausible pathway to refilling
SR calcium to maintain contractions in smooth muscle cells.
Time and Date: 2:453.35 p.m., Wednesday, October 12, 2005
Event: PIMS Tea
Location: WMAX Room 101 (PIMS Library)
Time and Date: 3:30 p.m., Wednesday, October 12, 2005
Event: Algebra Topology Seminar
Speaker: Marston Condor, University of Auckland
Subject:``Group actions on hyperbolic 3manifolds''
Location: WMAX Room 110
Abstract: Recently it was proved by Gehring, Marshall and Martin
(but not yet published) that the discrete subgroup of Iso(H^3)
of smallest covolume is the normaliser Gamma of the [3,5,3]Coxeter
group. Hence the hyperbolic 3manifolds with maximal symmetry group
are those of the form M = H^3/K where K is a torsionfree normal
subgroup of Gamma. (This makes Gamma the 3dimensional analogue
of the (2,3,7) triangle group in terms of its role in the Hurwitz
bound {m Aut}(S) le 84(g1) for a compact Riemann surfaces of given
genus g > 1.) In this talk I will describe methods for finding torsionfree
subgroups in Gamma, and constructions showing that infinitely many linear
fractional groups PSL(2,q) and PGL(2,q) and all but finitely many alternating
groups A_n and symmetric groups S_n are homomorphic images of Gamma and/or
its orientationpreserving subgroup Gamma^{+}. As a consequence of this
construction, we have an alternative proof of Kojima's theorem that
every finite group acts fixedpointfreely on some hyperbolic 3manifold.
This is joint work with Anna Torstensson (Lund) and Gaven Martin (Auckland).
Time and Date: 3:304:30 p.m., Wednesday, October 12, 2005
Event: Probability Seminar
Speaker: Chris Hoffman, U Washington
Subject:``Coexistence for Richardson type competing spatial growth models''
Location: WMAX Room 216
Abstract: In the Richardson growth model the vertices in Z^d can take on
three possible states 0,1, and 2. Vertices in states 1 and 2 remain in
their states forever, while vertices in state 0 which are adjacent to
a vertex in state 1 (or state 2) can switch to state 1 (or state 2).
We think of the vertices in states 1 and 2 as infected with one of two
infections while the vertices in state 0 are considered uninfected. We
start the models with a single vertex in state 1 and a single vertex is
in state 2. We show that with positive probability state 1 reaches an
infinite number of vertices and state 2 also reaches an infinite number
of vertices. The key tool is applying the ergodic theorem to stationary
first passage percolation.
Time and Date: 4:00 p.m., Wednesday, October 12, 2005
Event: IAM StudentFaculty Seminar
Speaker: Bo Wahlberg, Department of Signal, Sensors & Systems, Royal Institute of Technology, Stockholm, Sweden
Subject:``Modelling and Identification with Rational Orthogonal Basis Functions''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: Models of dynamical systems are of great importance in almost
all fields of science and engineering, and in particular in control and
signal processing. System identification deals with the problem of estimating
and validating such models from experimental data. By approximating the
frequency response of a linear timeinvariant system by a finite sum of
exponentials, the problem of modeling and identification is considerably
simplified. This corresponds to finite impulse response models in the
time domain. However, by using instead infinite impulse response transfer
functions as basis functions, much more efficient model structures can be
obtain. Over the last decades a general theory has been developed which
generalizes the work on Laguerre functions by Wiener in the 1930s, for
the construction and analysis of general rational orthogonal basis functions
models for the class of stable systems. The purpose of this presentation is
to give an introduction and to discuss some recent applications in system
identification of this theory. We will, in particular, discuss how to use
orthogonal statespace realization theory and a certain transformation analysis
to derive and analyze such models. The theory of rational orthogonal functions
is closely related to certain reproducing kernel spaces. This connection can
be used to analyze certain problems in system identification, and we will
present some recent results in the input design based on these results.
Time and Date: 3:003:50 p.m., Thursday, October 13, 2005
Event: SFU/UBC Number Theory Seminar at SFU
Speaker: Vishwa Dumir, Panjab University
Subject:``Viewobstruction problems''
Location: SFU Campus, Room ASB 10900
Abstract: We present a survey of the topic of viewobstruction problems
(generalizations of the problem of which lattice points are visible from
the origin) that will be accessible and interesting to graduate students
and researchers alike.
Time and Date: 4:005:00 p.m., Thursday, October 13, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker: Traian Pirvu, Department of Mathematics, UBC
Subject:``Satisfying Convex Risk Limits by Trading''
Location: WMAX Room 216
Abstract: We take as given a finite set of valuation and stress measures,
which we call scenario measures. With each scenario measure there is an
associated floor. These measures and floors determine if a random variable,
representing the wealth of an agent at the final time, is acceptable.
The central result of our paper is the characterization of random variables,
representing the wealth of an agent at a time prior to the final time,
from which the agent can trade to final acceptability. The representation
is surprisingly simple and shows, in particular, that if one cannot form
a martingale measure as a convex combination of scenario measures, then
the final acceptability condition imposes no constraint on the initial
wealth.
Furthermore we define buyer's and seller's prices for contingent
claims. These are like utility indifference prices, except they are based
on a concept of riskmeasure indifference. The buyer's and seller's prices
thus obtained are within the interval of superreplication and subreplication
prices, and in the case of a complete market, coincide with the expected.
Time and Date: 4:005:30 p.m., Thursday, October 13, 2005
Event: Complex Fluids Seminar
Speaker: Pengtao Yue, Department of Mathematics, UBC
Subject:``A finiteelement phasefield method for simulating interfacial
dynamics in complex fluids''
Location: MATH 225
Abstract: We present a novel and efficient finiteelement method for treating
interfacial problems involving rheologically complex fluids. Two key ingredients
of the method are a phasefield representation of the interface and an adaptive
meshing scheme that allows fine interfacial resolution at manageable
computational cost. In the phasefield framework, the interface is seen as a
thin layer across which material properties change rapidly but continuously.
Thus, a set of governing equations are derived that hold for both fluids across
the interface. This circumvents the cumbersome task of interface tracking. The
surface tension emerges from the mixing energy at the interface, and the
energybased formalism easily incorporates complex rheology. The challenge of
the method lies in resolving the interfacial layer on a fixed Eulerian grid.
This is handled by adaptive meshing on a unstructured grid using the
phasefield as the criterion for local refinement and coarsening. We will
present several simulations on drop deformation, retraction, coalescence and
breakup for Newtonian and viscoelastic liquids and nematic liquid crystals.
While some of these serve as validations of our new method, the results also
reveal novel physics governing the interplay between interfacial dynamics and
bulk rheology.
Time and Date: 4:105:00 p.m., Thursday, October 13, 2005
Event: SFU/UBC Number Theory Seminar
Speaker: Jason Bell, SFU
Subject:``A generalized SkolemMahlerLech theorem for affine varieties''
Location: SFU Campus, Room ASB 10900
Abstract: The SkolemMahlerLech theorem says that if f(n) is a linear
recurrence over a field of characteristic 0, then the set of n such that
f(n)=0 is a finite union of arithmetic progressions possibly augmented
by a finite set. In this talk, we prove the following generalization of
this result: Let X be an affine variety over a field of characteristic
0 with an automorphism s and subvariety Y. If x is a point in X, then
the set of integers n such that sn(x) ? Y is a finite union of twoway
arithmetic progressions possibly augmented by a finite set. We discuss
how this is a generalization of the classical SkolemMahlerLech theorem
and discuss recent progress in obtaining a positive characteristic analogue
of this result.
Time and Date: 3:00 p.m., Friday, October 14, 2005
Event: Mathematics Colloquium
Speaker: Jim Bryan, UBC
Subject:
``Topological Quantum Field Theory and its applications ancient and modern''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 3:004:00 p.m., Monday, October 17, 2005
Event: IAMPIMSMITACS Distinguished Colloquium Series
Speaker: Eitan Tadmor, Department of Mathematics, Institute for Physical Science & Technology,
Director of the Center for Scientific Computation and Mathematical Modeling,
University of Maryland
Subject:``Edge Detection, Hierarchical Decompositions and Velocity Averaging''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: I will discuss three separate problems which are dominated
by the presence of different scales. The first problem deals with edge
detection in noisy spectral data using separation of scales. The second
problem originates with image processing: I will present a novel representation
of texture which is decomposed into hierarchical scales of edges. I will conclude
with velocity averaging of kinetic to macroscopic scales, deriving new regularizing
effects in nonlinear secondorder equations.
Time and Date: 3:004:00 p.m., Monday, October 17, 2005
Event: Algebraic Geometry Seminar
Speaker: Naichung Conan Leung, CUHK, Hong Kong
Subject:``Mirror symmetry and magic square''
Location: WMAX Room 110 (PIMS)
Time and Date: 3:45 p.m., Monday, October 17, 2005
Event: Mathematics Tea
Location: MATX 1115, (Math Lounge)
Note: These refreshments precede the 4:00 p.m. Math Colloquium.
Time and Date: 4:00 p.m., Monday, October 17, 2005
Event: Mathematics Colloquium
Speaker: Michael Cowling, University of New South Wales
Subject:
``Mappings that preserve families of curves''
Location: MATH 104
Time and Date: 12:302:00 p.m., Tuesday, October 18, 2005
Event: SCAIM Seminar
Speaker: ChingShan Chou, Division of Applied Mathematics, Brown University
Subject:``High order residual distribution finite difference WENO schemes
for steady state conservation laws on nonsmooth meshes''
Location: MATX 1118
Abstract: High order conservative finite volume and finite difference methods
are widely used in solving hyperbolic conservation laws. Finite difference
schemes are preferred due to the smaller computational cost for multidimensional
problems. However, the restriction for using finite difference schemes is the
smoothness of the meshes.
In this talk, I will first compare these two schemes, and then introduce
another type of scheme, "Residual Distribution (RD) Schemes". Starting from
RD schemes, we are able to design high order RD finite difference WENO schemes
for steady state conservation laws. Our schemes have the cost comparable to
finite difference schemes on Cartesian or curvilinear meshes, but without any
smoothness assumptions of the meshes. Numerical results will be given. The
ongoing work for schemes generalized to convectiondiffusion equations and
preliminary numerical results will also be presented.
Time and Date: 3:304:30 p.m., Tuesday, October 18, 2005
Event: Discrete Mathematics Seminar
Speaker: Kristin Parton, Department of Mathematics, UBC
Subject:``Bounds on the Achromatic Number of Triple Systems''
Location: WMAX 216 (PIMS)
Abstract: A complete kcolouring of a hypergraph is an assignment of
k colours to the points such that (1) there is no monochromatic hyperedge,
and (2) identifying any two colours produces a monochromatic hyperedge.
The achromatic number of a hypergraph is the maximum k such that it
admits a complete kcolouring. This talk will present the maximum
possible achromatic number among all maximal partial triple systems
and give bounds on the maximum and minimum achromatic numbers of
Steiner triple systems.
Time and Date: 3:30 p.m., Tuesday, October 18, 2005
Event: DGMPPDE Seminar
Speaker: Hideo Takaoka, Kobe and Chicago
Subject:``Global wellposedness for the modified BenjaminOno equation in the energy space''
Location: WMAX 110 (PIMS)
Abstract: I will prove global existence of a solution for the cubic BenjaminOno
equation in the energy space. I will also discuss some illposedness issues. This is
joint work with Carlos Kenig.
Time and Date: 4:00 p.m., Tuesday, October 18, 2005
Event: Representation Theory Seminar
Speaker: Jose Antonio de la Pe~na, National University of Mexico
Subject:``Stable representations of quivers''
Location: MATH 203
Abstract: Objects that are stable for a certain slope were considered in
algebraic geometry for a long time. In particular stable vector bundles
and stable sheaves play an important role.
Let Q be a finite quiver without oriented cycles and k an algebraically closed
field. We investigate stable finite dimensional representations of Q. This includes,
HarderNarasimhan filtrations and wall systems. We consider distinguished slopes
which preserve the structure of the category of indecomposable representations of Q.
Time and Date: 4:30 p.m., Tuesday, October 18, 2005
Event: DGMPPDE Seminar
Speaker: Yiming Long, Nankai University, China
Subject:``Closed geodesics on 2 dimensional spheres''
Location: WMAX 110
Abstract: The study of closed geodesics on spheres is a
classical and important problem in both dynamical systems and differential geometry.
The results of V. Bangert in 1993 and J. Franks in 1992 prove that for every Riemannian
metric on S^2 there exist infinitely many geometrically distinct closed geodesics. In
1973, A. Katok constructed a remarkable irreversible Finsler metric on S^2 which
possesses precisely two distinct prime closed geodesics. Based on this result, D.V. Anosov
in his ICM report of 1974 proposed a question: "For the ndimensional sphere S^n, Katok's
example gives an irreversible Finsler metric, arbitrarily near to the `standard' metric
(to the metric of constant curvature) which has 2[n/2] closed geodesics. This number coincides
with the lower bound which one naturally expects for irreversible Finsler metrics on S^n and
which can be proved for metrics sufficiently near the `standard' metric". Here we denote
by [a]=max{k\in \Zk\leq a} for any a\in \R. Recently Victor Bangert and I proved the following
theorem which confirmed Anosov's conjecture for all Finsler 2spheres.
Theorem. (V. Bangert and Y. Long) For every Finsler metric F on the 2
sphere S^2, there exist at least two distinct prime closed geodesics.
In my lecture, I shall give a survey on this topic, talk about also some other new
results on the stability of closed geodesics, and mention some interesting and hard open problems
in this field.
Time and Date: 2:00 p.m., Wednesday, October 19, 2005
Event: Mathematical Biology Seminar
Speaker: Byron Goldstein, Los Alamos National Laboratory
Subject:``Immunoadhesins and monoclonal antibodies in the treatment of disease:
Modeling how they couple target cells to natural killer cells''
Location: WMAX 216 (PIMS)
Abstract: Natural killer (NK) cells can destroy cells coated with antibody.
The killing occurs at close range and requires that NK cells and target cells
adhere. The antibodies mediate adhesion and bridge the two cells by binding
to sites on the target cell through their Fab regions and by binding to Fc
receptors on the NK cells through their constant region. A number of monoclonal
antibodies and antibody like molecules have been developed and approved by the
FDA to target over expressed normal proteins on tumor cells and cells that drive
autoimmune diseases. We present a physical model of NK celltarget cell adhesion
mediated by these drugs. We illustrate the properties of the model and determine
important physical parameters by using it to fit quantitative data on adhesion
of T cells to NK cells mediated by a drug, Alefacept, used in the treatment of
psoriasis, an autoimmune disease of the skin. We discuss quantitative predictions
of the model, focusing on how drugs can discriminate among cells expressing the
same target molecules but with different surface densities. The model offers an
explanation of how Alefacept can distinguish target from normal T cells.
Time and Date: 2:453:35 p.m., Wednesday, October 19, 2005
Event: PIMS Tea
Location: WMAX 101 (PIMS Library)
Time and Date: 3:004:00 p.m., Wednesday, October 19, 2005
Event: Algebraic Geometry Seminar
Speaker: Prakash Belkale, University of North Carolina at Chapel Hill
Subject:``Intersection theory of homogenous spaces and sections of theta bundles on curves''
Location: MATX 1102
Abstract: Classically the intersection theory of Grasmannians is related
to invariant theory of the general linear group. I will talk about the
geometrization of this correspondence, and extension to geometrizations
of similar relations (Quantum cohomology of Grassmannians and sections of
theta bundles over moduli of parabolic bundles which is a theorem of Witten).
I will then speculate about the higher genus generalizations of such relations.
Time and Date: 3:304:30 p.m., Wednesday, October 19, 2005
Event: Probability Seminar
Speaker: Gabor Pete, UC Berkeley
Subject:``Corner percolation and the square root of 17''
Location: WMAX 216
Abstract: We consider a dependent bond percolation model on Z^2, introduced by
Balint Toth, in which every edge is present with probability 1/2, and each
vertex has exactly two incident edges, perpendicular to each other. We
prove that all components are finite cycles almost surely, but the
expected diameter of the cycle containing the origin is infinite.
Moreover, we derive critical exponents: for the tail probability,
\Pr(diameter of the cycle of the origin > n) \approx n^{\gamma}, and for
the expectation, \E(length of a cycle conditioned on having diameter n)
\approx n^\delta. We show that \gamma=(5\sqrt{17})/4=0.219... and
\delta=(\sqrt{17}+1)/4=1.28... The relation \gamma+\delta=3/2 corresponds
to the fact that the scaling limit of the natural height function in the
model is the Additive Brownian Motion, whose level sets have Hausdorff
dimension 3/2. The exponent \delta comes from the solution of a singular
sixth order ODE.
Time and Date: 4:00 p.m., Wednesday, October 19, 2005
Event: IAM StudentFaculty Seminar
Speaker: Omer Dushek, Department of Mathematics, UBC
Subject:``Calculating Diffusion Coefficients for Cell Surface Molecules
using the Fluorescence Recovery after Photobleaching (FRAP) Technique''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: A common technique for determining the diffusion coefficient of
cell surface molecules is Fluorescence Recovery After Photobleaching (FRAP).
In this technique, cell surface molecules are tagged with a fluorochrome
so that they can be seen under the microscope. In a certain region of
the cell surface, the fluorochromes are denatured, causing the
fluorescence in this region to decrease by a large amount (roughly 60
percent). Over time, the fluorescence recovers as receptors diffuse
back into this region. A popular equation to fit this data is an
approximate solution to the 1D diffusion equation. I will show that
the error in using this equation for the space and time scales of
experimental observation is quite large. I will then present an equation
more suitable for these scales.
Time and Date: 4:005:00 p.m., Thursday, October 20, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker: Artyom Shneyerov, Department of Economics, UBC
Subject:``Dynamic matching, twosided incomplete information, and participation costs:
existence and convergence to perfect competition''
Location: WMAX 216
Abstract: Consider a decentralized, dynamic market with an infinite horizon and
participation costs in which both buyers and sellers have private information
concerning their values for the indivisible traded good. Time is discrete, each
period has length ?, and each unit of time continuums of new buyers and sellers
consider entry. Traders whose expected utility is negative choose not to enter.
Within a period each buyer is matched anonymously with a seller and each seller
is matched with zero, one, or more buyers. Every seller runs a first price auction
with a reservation price and, if trade occurs, both the seller and winning buyer
exit the market with their realized utility. Traders who fail to trade continue
in the market to be rematched. We characterize the steadystate equilibria that
satisfy a subgame perfection criterion. We show that, as ? converges to zero,
equilibrium prices at which trades occur converge to the Walrasian price and the
realized allocations converge to the competitive allocation. We also show existence
of equilibria for ? sufficiently small.
Time and Date: 4:005:00 p.m., Thursday, October 20, 2005
Event: Graduate Student Seminar
Speaker: Amy Goldlist, Department of Mathematics, UBC
Subject:``The congruent number problem aka, fun with modular forms''
Location: MATX 1102
Abstract: An ancient Greek problem asks when a number, n, is the area of a right
angle triangle with rational sides. If it is, it is called congruent. Via
mathematical cunning, the problem of whether n is congruent can be transformed
into a question involving elliptic curves. From this step, the jump to modular
forms is not a huge stretch of the imagination. I plan on giving an expository
talk on the mathematics behind a condition for congruent numbers, and end up with
a "complete" answer to the question of whether n is congruent  modulo the
BirchSwinnertonDyer conjecture.
Time and Date: 4:005:00 p.m., Thursday, October 20, 2005
Event: Complex Fluids Lab Grand Opening
1st Speaker: David James, University of Toronto
2nd Speaker: Gareth McKinley, MIT
Subject:``1st talk: An Introduction to the World of Rheology"
Subject:``2nd talk: Elastocapillary thinning and beadsonastring"
Location: Leonard S. Klinck Bldg. Room 201
Note: The talks will be followed by a reception at 5:00 p.m.
in the new lab, LSK 203, all are cordially invited.
Time and Date: 3:00 p.m., Friday, October 21, 2005
Event: Mathematics Colloquium
Speaker: Prakash Belkale, UNC at Chapel Hill
Subject:
``Eigenvalue problem and a new product in the cohomology of flag varieties''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 2:45 p.m., Monday, October 24, 2005
Event: Mathematics Tea
Location: MATX 1115, (Math Lounge)
Time and Date: 3:004:00 p.m., Monday, October 24, 2005
Event: IAM Seminar Series
Speaker: Brian Wetton, UBC
Subject:``Modeling Hydrogen Fuel Cell Stacks''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: A basic introduction to the idea of a hydrogen energy economy
is given, with emphasis on the role of fuel cells. A reduced dimensional
model of steady state operation of Polymer Electrolyte Membrane Fuel Cell
(PEMFC) stacks with straight gas channels is then presented. The model takes
into account many important aspects of fuel cell operation and has been
developed to be an aid to fuel cell design in an industrial setting. The
structure of the model is a nonstandard system of boundary value Differential
Algebraic Equations (DAEs) with strong, nonlocal coupling. A discretization
of the system and a succesful iterative strategy is described. Some
preliminary analysis of the system and iterative strategy is given, using
simple, constant coefficient, linear versions of the key components of the
model. Representative computational results are shown. Some interesting
mathematical directions suggested by our group's modelling work will be
briefly presented.
Time and Date: 3:004:00 p.m., Monday, October 24, 2005
Event: Algebraic Geometry Seminar
Speaker: Jochen Kuttler, Department of Mathematics, UBC
Subject:``Blowing up certain singularities of Tvarieties in G/P''
Location: WMAX Room 110 (PIMS)
Abstract: In this talk we study singularities of Tvarieties in G/P, where
G is a semisimple algebraic group, P a parabolic subgroup and T a maximal
torus. Under good circumstances, isolated singularities are resolved by a
onestep blow up. In this case, one has also some control on the fibre
of the Nash blow up. The main application of course are Schubert varieties.
In parts this is joint work with Jim Carrell.
Time and Date: 12:302:00 p.m., Tuesday, October 25, 2005
Event: SCAIM Seminar
Speaker: Kees van den Doel, Department of Computer Science, UBC
Subject:``Level set regularization for highly illposed distributed
parameter estimation problems''
Location: MATX 1118
Abstract: The recovery of a distributed parameter surface with discontinuities
from inverse problems with elliptic forward PDEs is fraught with theoretical
and practical difficulties. Better results are obtained for problems where
the solution may take on at each point only one of two values, thus yielding
a shape recovery problem.
In this talk, after introducing the subject, I will describe my recent work
with Uri Ascher on level set regularization for such problems. Rather than
explicitly integrating a time embedded PDE to steady state, which typically
requires thousands of iterations, methods based on GaussNewton are applied
directly. One of these can be viewed as damped GaussNewton utilized to
approximate the steady state equations which in turn are viewed as the
necessary conditions of a Tikhonov type regularization with a sharpening
substep at each iteration. In practice this method is eclipsed, however,
by a special "finite time" trust region (or LevenbergMarquardt) method
which we call dynamic regularization applied to the output least squares
formulation.
The regularization functional is applied to the (smooth) level set function
rather than the discontinuous surface to be recovered, and the second focus
of this work is on selecting this functional. Typical choices may lead to
(or at least not avoid) flat level sets which in turn cause illconditioning
in that a small pointwise change in the level set function causes a large
change in its 0level and hence in the recovered surface. But the regularization
should also be selected so that its evolution is smooth, a particularly important
concern when large iteration updates are contemplated. We propose a new, quartic,
nonlocal regularization term and compare its performance to more usual choices.
Two numerical test cases are considered: a potential problem and the classical
EIT/DC resistivity problem.
Time and Date: 3:304:30 p.m., Tuesday, October 25, 2005
Event: Joint SFU/UBC Discrete Math/Computer Science Theory Seminar
Speaker: David Kirkpatrick, UBC
Subject:``Minimizing precision/input in the evaluation of geometric primitives''
Location: WMAX 216 (PIMS)
Abstract: Suppose that S is a collection of n points, each specified by kbit
coordinates. We want to determine some property of S: for example, does one
distinguished point in S lie in the interior of the convex hull of the rest.
For some instances S, all (or most) of the bits of all (or most) of the points
need to be examined in order to determine the property; for other instances the
property can be established by examining only a (relatively) small number of bits.
In general we would like to devise algorithms whose cost (number of bits examined)
adapts to the intrinsic cost (shortest "proof" of the property) for a particular input.
The problem of constructing such algorithms for certain simple geometric primitives
was posed by Leo Guibas. I will describe some preliminary results concerning
certain very basic questions of this type, based on joint work with Raimund Seidel.
Time and Date: 3:30 p.m., Tuesday, October 25, 2005
Event: DGMPPDE Seminar
Speaker: Adam Oberman, SFU
Subject:``Numerical Approximation of first and second order nonlinear elliptic PDEs
and stochastic game interpretations''
Location: WMAX 110 (PIMS)
Abstract: The theory of viscosity solutions gives powerful existence, uniqueness
and stability results for first and second order degenerate elliptic equations.
The approximation theory developed by Barles and Sougandis in the early nineties
gave conditions for the convergence of numerical schemes.
Building on this work, we develop convergent schemes for nonlinear second order
equations, including: infinity laplacian, motion by mean curvature, the MongeAmpere
equation, and the equation for the convex hull. Many of these equations also have
interpretations as stochastic control problems. We'll discuss this, and briefly give
discrete control interpretations of the schemes.
Time and Date: 2:00 p.m., Wednesday, October 26, 2005
Event: Mathematical Biology Seminar
Speaker: Nima Geffen, Mathematics, Tel Aviv University
Subject:``A micro helical organism revisited''
Location: WMAX 216 (PIMS)
Abstract: A spiroplasma, a helical prokaryot. is, arguably,
the smallest free swimming, autonomous living. It is driven by a linear protein
cytoskeleton that controls it's shape and motion. How is this effected?
A probable mechanism for a set of basic helical conformations will be reviewed,
and related to the rich repertoire of observed forms of the swimming organism.
New, possibly conflicting published data will be presented and discussed.
Time and Date: 2:453:35 p.m., Wednesday, October 26, 2005
Event: PIMS Tea
Location: WMAX 101 (PIMS Library)
Time and Date: 3:004:00 p.m., Wednesday, October 26, 2005
Event: Algebraic Geometry Seminar
Speaker: Shahn Majid, Queen Mary, University of London
Subject:``Noncommutative differential geometry and the origin of time''
Location: MATX 1102
Abstract: Noncommutative geometry is a more general formulation of geometry
that does not require coordinates to commute. As such it unifies quantum theory
and geometry and should appear in any effective theory of quantum gravity. In
this general talk we present quantum groups as a microcosm of this unification
in the same way that Lie groups are a microcosm of usual geometry. We use them
to construct differential structures on finite groups or `finite Lie theory'. We
also explain that noncommutative spaces typically carry a canonical 1parameter
evolution or intrinsic time created from the fundamental conflict between noncommuting
coordinates and differential calculus.)
Time and Date: 3:304:30 p.m., Wednesday, October 26, 2005
Event: Probability Seminar
Speaker: Vlada Limic, UBC
Subject:``The spatial Lambdacoalescent''
Location: WMAX 216
Abstract: This talk is based on a joint paper with Anja Sturm, and it will
describe the extension of the Lambdacoalescent of Pitman (1999) to
the spatial setting. The partition elements of the spatial
Lambdacoalescent migrate in a (finite) geographical space and may
only coalesce if located at the same site of the space. We
characterize the Lambdacoalescents that come down from infinity, in
an analogous way to Schweinsberg (2000). Surprisingly, all spatial
coalescents that come down from infinity, also come down from infinity
in a uniform way. This enables us to study spacetime asymptotics of
spatial Lambdacoalescents on large tori in transient dimensions. Our
results generalize and strengthen those of Greven et al. (2005), who
studied the spatial Kingman coalescent in this context.
Time and Date: 4:00 p.m., Wednesday, October 26, 2005
Event: IAM StudentFaculty Seminar
Speaker: Dan Coombs, UBC
Subject:``Understanding parasite fitness in simple models''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: Viruses compete and are subject to natural selection at multiple
levels: withincell, withinhost and withinpopulation (of hosts). We
looked at how viruses can optimally exploit their hosts and how this
behaviour may influence the most successful strategy at the betweenhost,
or epidemiological level. I'll illustrate this all as best I can and try
not to be boring or confusing.
Time and Date: 3:003:50 p.m., Thursday, October 27, 2005
Event: SFU/UBC Number Theory Seminar at UBC
Speaker: Nigel Boston, University of Wisconsin
Subject:``Galois groups of pextensions and applications''
Location: UBC Campus, WMAX 110 (PIMS Seminar Room)
Abstract: Unlike the ramifiedatp case, Galois groups of pextensions
unramified at p are poorly understood, partly because they should have
only finiteimage padic representations. We present an analogous theory
of arboreal representations, a nonabelian Jugendtraum, and nonabelian
CohenLenstra heuristics. Applications of this theory to rootdiscriminant
problems, algebraic topology, and group theory have emerged.
Time and Date: 4:005:00 p.m., Thursday, October 27, 2005
Event: Complex Fluids Seminar
Speaker: Teodor Burghelea, Department of Mathematics, UBC
Subject:``Chaotic flow and mixing with a dilute polymer solution
in a regime of elastic turbulence''
Location: MATH 225
Abstract: I present an experimental investigation of random flows of a
dilute polymer solution above the onset of the elastic instability
in both closed and open flow configurations [1]. Systematic
investigation [2,3] of micro flows of a dilute polymer solution has
shown that, when elastic stresses overcome the
viscous ones (Wi>1), the micro flow becomes quite irregular and
evolves (as Wi is further increased) rapidly towards a fully
developed chaotic regime. Although the typical size of the elongated
polymer molecules is likely to become comparable to the diameter of
the micro channel , we show that the random micro flow of a dilute
polymer solution surprisingly displays most of the features of
elastic turbulence (Groisman and Steinberg, Nature, 2000) in
geometrically similar macro flows: \emph{fast growth of flow
resistance, randomly varying and strongly fluctuating velocity
fields, fast and monotonous decay of the Eulerian velocity
correlations}.
The random microscopic flow turns out to be an ideal realization of
the Batchelor regime of mixing. By studying the mixing efficiency at
different Peclet numbers (Pe), we confirm a very recent
theoretical prediction (Chertkov and Lebedev, 2003): the mixing
efficiency scales algebraically with Pe. This difference with
respect to the case of the Batchelor regime in an unbounded system
is further clarified by systematic measurements of the width of the
mixing boundary layer as a function of Pe.
Finally, we characterize the flow randomness in a regime of elastic
turbulence by focusing on the statistics of particle pair
separations [1,4]. We compare the Finite Time Lyapunov
Exponents (FTLE) with the statistical description in Eulerian
frame, namely velocity correlation times and average velocity
gradients.
Time and Date: 4:105:00 p.m., Thursday, October 27, 2005
Event: SFU/UBC Number Theory Seminar
Speaker: Patrick Ingram, Department of Mathematics, UBC
Subject:``Primitive divisors in elliptic divisibility sequences''
Location: UBC Campus, WMAX 110
Abstract: A divisibility sequence is a sequence of intregers {an} with
the property that an divides am whenever n divides m. We will survey the
literature on divisibility sequences and consider various problems
relating to elliptic divisibility sequences, a certain class of sequences
arising from the study of elliptic curves. In particular, we will ask whether
the terms in such a sequence must eventually all have primitive divisors,
that is, divisors that divide no previous term in the sequence.
Time and Date: 3:00 p.m., Friday, October 28, 2005
Event: Mathematics Colloquium
Speaker: Nigel Boston, University of Wisconsin
Subject:
``Invariantbased Face Recognition''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 2:45 p.m., Monday, October 31, 2005
Event: Mathematics Tea
Location: MATX 1115, (Math Lounge)
Time and Date: 3:004:00 p.m., Monday, October 31, 2005
Event: IAM Seminar Series
Speaker: Neil Balmforth, Department of Mathematics, UBC
Subject:``Snailballs and More''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: The "snailball" is a magic trick wherein an apparently solid metal
sphere rolls slowly and erratically down an inclined plane. The key to the trick
is that the sphere is not actually solid throughout, but a shell containing a
second, smaller sphere with a very viscous fluid sandwiched between. As will be
demonstrated in the seminar, the same phenomenon occurs when a combination of
cylinders rolls down a surface. A mathematical model of the latter is presented
to explore in more detail the motions of the two cylinders. A key feature of the
predicted dynamics is that the inner cylinder cannot be suspended in the fluid
by the rolling motion of the outer cylinder. Instead, it must always fall toward
the outer cylinder and "contact". The rocking and rolling motion of the real
cylinders must then incorporate a key extra physical detail, namely what happens
when the cylinder surfaces become very close. Two possibilities are discussed:
contact between rough surface, and cavitation.
Time and Date: 3:004:00 p.m., Monday, October 31, 2005
Event: Algebraic Geometry Seminar
Speaker: Konstanze Rietsch, King's College, University of London
Subject:``Mirror families for flag varieties G/P and the Peterson variety''
Location: WMAX 110 (PIMS)
Abstract: We give a Lietheoretic construction of a conjectural mirror family
in the sense of Givental to a general flag variety G/P, and show that this
mirror family recovers the Peterson variety presentation for the quantum
cohomology rings qH^*(G/P)_{(q)}. As a nice application one can use this
approach to describe the totally nonnegative part of the Peterson variety
in type A.
Time and Date: 12:302:00 p.m., Tuesday, November 1, 2005
Event: UBC SCAIM Seminar
Speaker: Ian Mitchell, Department of Computer Science, UBC
Subject:``Some Algorithms, Software and Applications of HamiltonJacobi PDEs''
Location: MATX 1118
Abstract: HamiltonJacobi type (HJ) PDEs arise in optimal control, dynamic
implicit surfaces for fluid animation and simulation, image
processing, and many other fields. There are two broad classes of
equations: timedependent and stationary. Level set methods are a
group of finite difference algorithms for the former class of
equations, and I will describe a publicly released toolbox of Matlab
routines for approximating a wide variety of common HJ forms in any
dimension. I will then describe and analyze a new algorithm for
solving the stationary form of HJ equations. Finally, I will discuss
applications of each of the two forms: reachable sets for the
verification of continuous systems, and optimal path planning with
multiple objectives.
Time and Date: 3:304:30 p.m., Tuesday, November 1, 2005
Event: Joint SFU/UBC Discrete Math/Computer Science Theory Seminar
Speaker: Jason Bell, Department of Mathematics, SFU
Subject:``New Methods in the theory of Quasiinvariants''
Location: WMAX 216 (PIMS)
Abstract: We introduce a new approach to the study of quasiinvariants. This
approach consists of representing quasiinvariants as ntuples of invariants.
Conditions are then sought which characterize such ntuples. These methods
explain certain observed properties of quasiinvariants. This is joint work
with A. Garsia and N. Wallach.
Time and Date: 3:30 p.m., Tuesday, November 1, 2005
Event: DGMPPDE Seminar
Speaker: Ivar Ekeland, PIMS, UBC
Subject:``A remarkable PDE arising from noncommitment in economics''
Location: WMAX 110 (PIMS)
Abstract: (joint work with Ali Lazrak and Louis Nirenberg) Optimal control
theory has been used to study economic policy. It is not robust, however,
to noncommitment by the policy maker. We propose an alternative approach,
leading to a remarkable variant of the HamiltonJacobi equation.
Time and Date: 2:00 p.m., Wednesday, November 2, 2005
Event: Mathematical Biology Seminar
Speaker: Nick Swindale, Department of Ophthalmology & Visual Sciences, UBC
Subject:``Coverage, Polymaps and the Visual Cortex''
Location: WMAX 216 (PIMS)
Abstract: In this talk I will present some simple mathematical models that
are able to explain the structure of the maps that are found in the mammalian
visual cortex. These can be characterized as projections of a 2D surface into
a high dimensional feature space subject to completeness and local continuity
constraints.
Time and Date: 2:453:35 p.m., Wednesday, November 2, 2005
Event: PIMS Tea
Location: WMAX 101 (PIMS Library)
Time and Date: 3:30 p.m., Wednesday, November 2, 2005
Event: Algebra Topology Seminar (This was postponed on Oct. 24, 2005 until Nov. 2nd)
Speaker: Denis Sjerve, UBC
Subject:``Invariant Spin Structures on Hyperelliptic Surfaces''
Location: WMAX 110
Abstract: Atiyah proved that any automorphism of a Riemann surface M of genus
at least 2 leaves invariant some spin structure. This raises several questions:
how many spin structures are invariant? does the entire automorphism group leave
some spin structures invariant? etc.
In this talk I will show how to answer the first question for hyperelliptic
surfaces.
Time and Date: 3:304:30 p.m., Wednesday, November 2, 2005
Event: Probability Seminar
Speaker: JeanFrancois Delmas, CERMICS, France
Subject:``Fragmentation of the continuous random tree''
Location: WMAX 216
Abstract: We consider the height process of a Lévy process with no negative jumps,
and its associated continuous tree representation. Using Lévy snake tools
developed by DuquesneLe Gall, with an underlying Poisson process, we construct
a fragmentation process, which in the stable case corresponds to the selfsimilar
fragmentation described by Miermont. For the general fragmentation process we
compute a family of dislocation measures as well as the law of the size of a
tagged fragment.
Time and Date: 4:00 p.m., Wednesday, November 2, 2005
Event: IAM StudentFaculty Seminar
Speaker: Daniel Olmos, Department of Mathematics, UBC
Subject:``A Numerical Study of Excitable Systems''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: Excitable systems are often modelled with reactiondiffusion equations
with kinetic terms of varying complexity. The solution of such reactiondiffusion
systems is characterized by many different time and length scales. In the
present talk, I will discuss the classical HodgkinHuxley (HH) model as an
example of excitability. After, I will explain the problem of the different
time and space scales in systems like the (HH) model, followed by a
description of the purpose of my research, which is focused on the numerical
simulation of excitable systems. More specifically my research work is
directed towards the development of spectral methods for the resolution of
the fast and slow dynamics with high accuracy and low computational cost.
Time and Date: 4:005:00 p.m., Thursday, November 3, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker: Calvin Winter, President, Alpha Lake Financial Analytics Corp.
Subject:``Mathematical Methods applied to Finance Trading Strategies''
Location: WMAX 216
Abstract: We consider the implications of the arbitrage free
condition applied to markets. By considering systematic trading
strategies we show that arbitrage free implies: instantaneous
adjustment by the market to news; short term volatility is linked
to long term volatility by the convolution of the time varying
probability distribution functions or as (time)1/2 in the
Gaussian case. In the special case of continuous markets then
volatility itself becomes tradable and must be arbitrage free, in
addition we derive an expression for arbitrage free bidask spread
which is volatility dependent.
Deviations of real market behavior from the arbitrage free case
can sometimes provide helpful clues to assist in constructing
systematic trading strategies.
Time and Date: 4:005:00 p.m., Thursday, November 3, 2005
Event: Graduate Student Seminar
Speaker: Yinan Song, Department of Mathematics, UBC
Subject:``Introduction to Lie algebras and their representations''
Location: MATX 1102
Abstract: In this introductory talk, I will define Lie algebra and I will
describe a particular infinite dimensional Lie algebra, the Heisenberg algebra.
Finally, I will describe how the Heisenberg algebra acts on the homology groups
of Hilbert schemes of points on a surface.
Time and Date: 4:005:00 p.m., Thursday, November 3, 2005
Event: Complex Fluids Seminar
Speaker: Laurent Rubatat, Department of Physics, SFU
Subject:``Probing the microstructure of carbopol
using dynamic light scattering and multiple particle tracking''
Location: MATH 225
Abstract: We study the microrheology of dispersions of Carbopol
ETD 2050 in water as a function of the gel concentration. To do so, we use
dynamic light scattering and optical microscopy to track submicron spherical
particles loaded in the gel, with diameter ranging from 50 nm to 1 mm. The
Mean Square displacement (MSD) of the particles is calculated and analyzed
to obtain the complex mechanical modulus of the gel on micrometer length scales.
For low Carbopol concentrations (0.1%), the spheres diffuse. At moderate
concentrations (0.5%) there is subdiffusion as the structure of the fluid
constrains the sphere motion. At high concentrations (1%), the Carbopol is a
stiff gel and the particles are almost completely confined. The results
obtained by microscopy and dynamic light scattering are in good agreement.
In contrast, we find substantial differences between our microscale
measurements and the results of lassical shear rheometry. We will discuss
the difference between the bulk results and the microscale results in the
context of the gel structure.
Time and Date: 3:00 p.m., Friday, November 4, 2005
Event: Mathematics Colloquium
Speaker: Michael Thaddeus, Columbia University
Subject:
``Holomorphic curves on infinitedimensional homogeneous spaces''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 2:45 p.m., Monday, November 7, 2005
Event: Mathematics Tea
Location: MATX 1115, (Math Lounge)
Time and Date: 3:004:00 p.m., Monday, November 7, 2005
Event: IAMPIMSMITACS 20052006 Distinguished Colloquium Series
Speaker: Gregory Kriegsmann, Foundation Chair of Applied Mathematics, Professor of Mathematics,
Department of Mathematical Sciences, New Jersey Institute of Technology
Subject:``Microwave Heating of Materials: A Mathematical and Physical Overview''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: The use of microwaves to heat and dry materials is rapidly gaining acceptance in industry and, to some extent, in the field of biomedical engineering. The working engineering theories are based upon heuristically averaged, linear equations which adequately explain some processes, such as microwave cooking of foodstuffs, but not others. These include such phenomenon as thermal runaway and hotspot formations which have important ramifications in both biomedical and industrial applications. They are caused by the temperature dependencies of the electrical and thermal properties of the irradiated material which make the basic underlying mathematical description highly nonlinear. We shall describe several microwave heating experiments and present models which have been used by researchers in this field. The strengths and shortcomings of these models will be discussed, and open questions of both mathematical and computational natures will be presented.
Time and Date: 3:004:00 p.m., Monday, November 7, 2005
Event: Algebraic Geometry Seminar
Speaker: Yinan Song, Department of Mathematics, UBC
Subject:``GromovWitten/DonaldsonThomas correspondence''
Location: WMAX 110 (PIMS Seminar Room), 1933 West Mall, UBC
Abstract: I will discuss the conjectural correspondence of GromovWitten/DonaldsonThomas theories of threefolds with focus on the theoretical and computational aspects of DonaldsonThomas theory. I will also discuss some recent results on P^2bundle over a smooth curve that provide some evidence for this conjecture.
Time and Date: 3:304:30 p.m., Tuesday, November 8, 2005
Event: Joint SFU/UBC Discrete Math/CS Theory Seminar
Speaker: Luis Goddyn, SFU
Subject:``An Optimization Problem arising from Videoon Demand Broadcasting''
Location: WMAX 216 (PIMS)
Abstract: A common protocol (FDPB) for videoondemand specifies that a
large document (a movie) be divided into consecutive time segments
s_1, \dots, s_n. The segments are continually broadcast through
a single channel according to a specified periodic schedule
such as s_1, s_5, s_2, s_1, s_3, s_4, s_1, s_2, s_3, \dots.
A client may, at any time, decide to watch the movie.
Segments s_i with a small subscript i should appear frequently
in the schedule, so the viewer does not have to wait long for the
movie to begin. Segments with large i may appear less frequently
since they can be loaded while the movie is already playing.
An optimal schedule minimizes the initial delay time while guaranteeing
that the movie does not have to pause to await a missing segment.
A (patented) solution to this problem involves a "roundrobin tree".
To implement their protocol efficiently, one must solve the following
optimization problem. Given a large positive integer n_0,
we seek a positive integer d which maximizes n_d, where
n_1, n_2, \dots, n_d are defined by
n_{i+1} = n_i + \floor( n_i / d ), 0 \le i < d.
For a fixed n_0, the value of n_d behaves erratically as a
function of d. We show that the optimal value of d
can be determined by examining a small interval centred
at 1.2578 \sqrt{ n_0 }. This greatly improves the lineartime
search proposed by the patent holders (Hollmann et al, 1995).
This is joint work with T. Kameda and Y. Sun.
Time and Date: 3:30 p.m., Tuesday, November 8, 2005
Event: DGMPPDE Seminar
Speaker: Nassif Ghoussoub, BIRS, UBC
Subject:``On the Partial Differential Equations of Electrostatic MEMS Devices''
Location: WMAX 110 (PIMS)
Abstract: I will be talking about work with Yujin Guo on the nonlinear
parabolic problem u_t=\Delta u \frac{\lambda f(x)}{(1+u)^2} on a bounded domain
\Omega of \R^N with Dirichlet boundary conditions. This models a simple electrostatic
MicroElectromechanical System (MEMS) device consisting of a thin dielectric elastic
membrane with boundary supported at 0 above a rigid ground plate located at 1. When
a voltage represented here by \lambda is applied, the membrane deflects towards
the ground plate and a snapthrough may occur when it exceeds a certain critical value \lambda^*.
This equation suggested by Michael Ward turned out to be a rich source of interesting
mathematical phenomena. Numerics give lots of information and point to many conjectures,
and the existing arsenal of nonlinear analysis and PDE techniques can only tackle a precious few.
Refined properties of steady states such as regularity, stability, uniqueness, multiplicity,
energy estimates and comparison results are shown to depend on the dimension of the
ambient space. I will also describe some of the results and questions in the dynamic case:
Touchdown or not, in finite or infinite time.
Time and Date: 2:00 p.m., Wednesday, November 9, 2005
Event: Mathematical Biology Seminar
Speaker: Lin Wang, University of Victoria
Subject:``Competition in the chemostat''
Location: WMAX 216 (PIMS)
Abstract: In this talk, a chemostat model with general
nonmonotone response functions is considered. The nutrient conversion process
involves time delay. It is shown that under certain conditions, when several
species with differential removal rates compete in the chemostat for a single
resource that is allowed to be inhibitory at high concentrations, the competitive
exclusion principle (CEP) holds.
In addition, a local stability analysis is provided that includes sufficient
conditions for the bistability of the single species survival equilibrium and
the washout equilibrium, thus showing initial condition dependent outcome is
possible.
This talk is based on joint work with G.S.K. Wolkowicz (McMaster University).
Time and Date: 2:453:35 p.m., Wednesday, November 9, 2005
Event: PIMS Tea
Location: WMAX 101 (PIMS Library)
Time and Date: 3:304:30 p.m., Wednesday, November 9, 2005
Event: Probability Seminar
Speaker: Omer Angel, UBC
Subject:``Onedimensional DLA''
Location: WMAX 216
Abstract: Diffusion limited aggregation (DLA) in 2 or more dimensions is an infamously difficult model for the growth of a random fractal. DLA was introduced in 1981 and attracted massive attention (63,400 google results for "diffusion limited aggregation"). Kesten's 1987 upper bound is almost the only proven result on it.
We define a variation of DLA in one dimension. This becomes interesting when the random walk generating the DLA has arbitrary long jumps. It turns out that the growth rate of the aggregate depends on the step distribution in complex ways. In particular there are three phase transitions in the behaviour when the step distribution has finite expectation, finite variance, and finite third moment.
Joint work with Gidi Amir, Itai Benjamini and Gadi Kozma.
Time and Date: 4:00 p.m., Wednesday, November 9, 2005
Event: IAM StudentFaculty Seminar
Speaker: George Bluman, UBC
Subject:``Connections between symmetries and conservation laws''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: pdf link: http://www.emis.de/journals/SIGMA/2005/.
The classical Noether's Theorem yields conservation laws arising
from continuous symmetries of functionals whose extrema solve the
corresponding EulerLagrange equations. After reviewing Noether's Theorem
and its severe limitations, we present the Direct Construction Method to
find directly the CLs for any given system of differential equations. The
DCM yields the factors for CLs as well as an integral formula for
corresponding conserved densities. The factors are symmetries of the given
system of DEs if and only if the given system has a variational
principle. The action of a symmetry (discrete or continuous) on a
conservation law yields conservation laws. Conservation laws of a given
system of DEs yield nonlocally related systems that, in turn yield
algorithms to obtain nonlocal symmetries (and nonlocal conservation laws as
well as extensions of qualitative, numerical and perturbation methods) for
a given system. Moreover from its admitted symmetries or factors for
conservation laws, one can determine whether or not a given system of PDEs
can be linearized by an invertible transformation and find its
linearization when it exists. All of these connections are
algorithmic. Examples will be given and some open problems will be
presented.
Time and Date: 3:003:50 p.m., Thursday, November 10, 2005
Event: SFU/UBC Number Theory Seminar at SFU
Speaker: Greg Martin, UBC
Subject:``Smooth numbers, primes, and Egyptian fractions''
Location: SFU Campus, Room ASB 10900
Abstract: This will be an expository talk about smooth numbers (numbers without large prime factors) and their connection to the distribution of prime numbers, particularly prime values of polynomials. An application to questions on Egyptian fractions (sums of reciprocals of distinct positive integers) will ensue, mainly as an excuse to bring in some of the speaker's old research. The entire talk will be accessible to students and nonexperts.
Time and Date: 4:005:00 p.m., Thursday, November 10, 2005
Event: Complex Fluids Seminar
Speaker: Andreas Putz, Department of Mathematics, UBC
Subject:``Plug breaking and walllayer formation in a wavy walled channel flow''
Location: MATH 225
Abstract: We show numerical simulation results for the Poiseuille flow of a Bingham
fluid down a wavywalled channel, at long wavelengths. For small amplitude
perturbations of the plane channel, the rigid plug region remains intact,
but breaks at a critical amplitude. The asymptotic theory in [1] predicts
both the shape of the perturbation of the yield surface and the critical
amplitude when the plug breaks. Counterintuitively, the unyielded plug is
wider in the narrower part of the channel and narrower in the wider part.
Numerically, this is a challenging problem. For high accuracy in a channel
of large aspect ratio, a large number of cells are required. Regularisation
methods are inappropriate for such geometries and anyway do not necessarily
predict the correct yield surface position. We have used finite elements
with the augmented Lagrangian method, coupled with an adaptive meshing
technique that focuses the mesh close to the yield surface, see [2].
The numerical results confirm the results of [1]. Unequivocally, this means
that the lubrication paradox of [3] is in fact no paradox, i.e. it is simply
that appropriate numerical and asymptotic methods must be applied. The
numerical results are able to reveal more of the flow structure than the
results in [1]. In particular, we determine the shape of the plug region
during breaking. We also investigate larger amplitude wall perturbations at
significant Bingham numbers, B. Here we show that a unyielded plug begins to
form on the wall in the widest part of the channel, at a critical amplitude.
It is not apparently necessary for the plug to break, since the static
walllayer blocks the channel allowing a faster plug velocity at the channel
centre, which reduces the stresses.
Refs:
[1] Ryan & Frigaard
[2] Saramito
[3] Lipscomb & Denn
Time and Date: 4:105:00 p.m., Thursday, November 10, 2005
Event: SFU/UBC Number Theory Seminar at SFU
Speaker: Peter Borwein, SFU
Subject:``The Riemann Hypothesis  not necessarily for experts''
Location: SFU Campus, Room ASB 10900
Time and Date: 3:004:00 p.m., Monday, November 14, 2005
Event: IAM Seminar Series
Speaker: Peter Berg, Faculty of Science, University of Ontario Institute of Technology
Subject:``Linking Cellular Automata and OptimalVelocity Traffic Models through Wave Selections at Bottlenecks''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: Cellular automata (CA) models have been widely used to simulate traffic flow on highways
and road networks, in particular the NagelSchreckenberg (NS) model. Together with carfollowing and continuum models,
they represent the three most popular classes of traffic models.
In this talk, we will investigate a bottleneck simulation of road traffic on a loop, using the NS model. Three types
of stationary wave solutions emerge. They consist of:
a. two shock waves at the bottleneck boundaries,
b. one shock wave at the boundary and one on the 'open' road, and
c. the trivial solution, i.e. homogeneous uniform flow.
These solutions are selected dynamically from a range of kinematically possible solutions. This is similar in fashion
to the wave selection in a bottleneck simulation of the optimalvelocity (OV) carfollowing model, a coupled system of
ODEs. It is also one of the strongest indications todate that CA and OV models share certain underlying dynamics,
although the former are discrete in space and time while the latter are continuous.
Time and Date: 12:302:00 p.m., Tuesday, November 15, 2005
Event: UBC SCAIM Seminar
Speaker: Evgeny Sorkin, Department of Physics & Astronomy, UBC
Subject:``Critical collapse of a scalar field in higher dimensional spacetime''
Location: MATX 1118
Abstract: The scaling phenomenon found in general relativistic critical
gravitational collapse of a massless scalar field is extended to
higher dimensions. We find that in the range 4 <= D <= 11 of the
spacetime dimension the behavior is qualitatively similar to that
originally discovered by Choptuik in 4D, back in 1992. In each
dimension we obtain numerically the universal numbers associated with
the critical collapse: the scaling exponent gamma and the echoing
period Delta. The behavior of these numbers with increasing
dimension seems to indicate that gamma reaches a maximum and Delta a
minimum value around 11 <= D <= 13. These results and their relation
to the phase transition in the higherdimensional black holeblack
string system are discussed.
Time and Date: 3:304:30 p.m., Tuesday, November 15, 2005
Event: Joint SFU/UBC Discrete Math/Computer Science Theory Seminar. Cancelled Nov. 14th due to illness.
Speaker: John Bueti, UCLA
Subject:``A combinatorial result for the (n,k) problem''
Location: WMAX 216 (PIMS Seminar Room), 1933 West Mall, UBC
Abstract: The (n,k) problem is a variant of the Kakeya problem which asks one to determine a lower
bound on the size of a set E contained in the vector space F^n (for some large finite field F) which has the property
that E contains a translate of every kdimensional subspace of F^n. In this talk, we will discuss a bound for the
associated maximal function operator whose proof depends entirely upon incidence combinatorics.
Time and Date: 3:30 p.m., Tuesday, November 15, 2005
Event: DGMPPDE Seminar
Speaker: Nataliya Ivanova, Department of Mathematics, UBC
Subject:``On symmetry properties of nonlinear Schrodinger equations''
Location: WMAX 110 (PIMS Seminar Room)
Abstract: The complete group classification in the class of Schrodinger equations with power
nonlinearity and potential term is performed. We construct all possible inequivalent potentials for which these
equations have nontrivial Lie symmetries. All admissible transformations in the class under consideration are found.
The obtained results are used to derive some results on existence and uniqueness of solutions of Cauchy problem.
Time and Date: 4:00 p.m., Tuesday, November 15, 2005
Event: Algebraic Geometry Seminar
Speaker: Vladimir Chernousov, University of Alberta
Subject:``Motivic decomposition of projective homogeneous varieties and the KrullSchmidt theorem''
Location: MATX 1118
Abstract: We discuss the problem of decompositon of a motive of the product of two projective
homogeneous Gvarieties into a direct sum of twisted motives of projective homogeneous Gvarieties and uniqueness
of such decompositions.
Time and Date: 2:00 p.m., Wednesday, November 16, 2005
Event: Mathematical Biology Seminar
Speaker: Neil Balmforth, UBC
Subject:``Locomotion of Gastropods: Lubrication theory plus RoboSnail''
Location: WMAX 216 (PIMS)
Abstract: Many gastropods, such as slugs and snails, crawl via adhesive locomotion in which the
foot sends waves over a fluid layer between the creature and the underlying surface. We investigate this method of
propulsion using two mathematical models, one for direct waves and one for retrograde waves. We then test the
effectiveness of both proposed mechanisms by constructing two mechanical crawlers. Each crawler uses a different
mechanical strategy to move on a thin layer of fluid. The first uses a flexible flapping sheet to generate lubrication
pressures in a Newtonian fluid which in turn propels the mechanical snail. The second generates a wave of compression
on a layer of Laponite, a nonNewtonian, finiteyield stress fluid with characteristics similar to those of snail mucus.
This second design can climb smooth vertical walls and perform an inverted traverse.
Time and Date: 2:003:00 p.m., Wednesday, November 16, 2005
Event: Mathematics Colloquium hosted by PIMS & UBC
Speaker: Heinz Bauschke, UBC Okanagan
Subject:
``Projection methods  a guided tour''
Location: MATH 103
Please plan to attend the PIMS hosted Tea and refreshments after the colloquium in WMAX 101.
Time and Date: 2:453:35 p.m., Wednesday, November 16, 2005
Event: PIMS Tea
Location: WMAX 101 (PIMS Library)
Time and Date: 3:30 p.m., Wednesday, November 16, 2005
Event: Algebra Topology Seminar
Speaker: Dale Rolfsen, UBC
Subject:``The Poincare conjecture and its cousins''
Location: WMAX 110
Abstract: For a hundred years, topologists have attacked the PC, sometimes by finding equivalent
algebraic or topological conjectures, which might "reduce" the problem. Now that the PC has (reputedly) been solved
by a differential geometer, some of these other problems are also solved  the reverse of the expected order of things.
And some are not. My talk will be a survey of some of these "cousins" of the PC.
Time and Date: 3:304:30 p.m., Wednesday, November 16, 2005
Event: Probability Seminar
Speaker: Rick Durrett, Cornell University
Subject:``Waiting for ATCAAAG''
Location: WMAX 216
Abstract: One possible explanation for the substantial organismal differences that have developed
in the 6 million years sincee the divergence of humans and chimpanzees is that there have been changes in gene regulation.
The word in the title is a sample transcription factor binding sites and motivates the following probability question:
given a 1000 nucleotide region in our genome, how long does it take for a specified six to nine letter word to appear
in that region in some individual? Stone and Wray (2001) computed 5949 years as the answer for six letter words in the
human population. We will show that for words of length 6, the average waiting time is 100,000 years while for words of
length 8, the waiting time is roughly a 1/3  2/3 mixture of exponentials with means 375,000 years and 625 million years.
In biological reality, the match to the target word does not have to be perfect for binding to occur. If we model this
by saying that we allow mismatch, then almost all of the mass in the probability distribution shifts to the smaller mean.
This is joint work with Deena Schmidt.
Time and Date: 4:00 p.m., Wednesday, November 16, 2005
Event: IAM StudentFaculty Seminar
Speaker: Shreyas Mandre, Department of Mathematics, UBC
Subject:``Pouring things down an incline and related flows''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: It is common knowledge that water runs down an incline, so do other
liquids. But as they flow down, I will begin by show some interesting things that
may happen, followed by a discussion on the motivation for studying such flows. One
of the observations on such flows is the propagation of waves and I will briefly
explain the mechanism behind their formation.
The problem of flow down an incline is related to a few others, for example the
flow of air past vocal cords generating speech. For the second part, I will
allude to the mechanism of processes like speech generation in somewhat detail
and conclude by mentioning some future work and open problems.
Time and Date: 4:005:00 p.m., Thursday, November 17, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker: Biao Wu, School of Mathematics and Statistics, Carleton University
Subject:``Interacting Systems in Timevarying and Random Environments''
Location: WMAX 216
Abstract: Two topics of interacting systems will be covered in this talk: A) multiagent models and B) interacting agent feedback
finance models.
In the multiagent models, there exist a closed system of N agents who are classified into r types with respect to their
states of an internal system. Each agent can change its type by its observation of the performances of the internal states
or by the relative frequency of different internal states among the others (the latter is called multinomial sampling,
which is one source of interaction). The multiagent models with multinomial sampling are related to the WrightFisher
model. The asymptotic behavior of multiagent models are studied by the weak convergence criteria for timeinhomogeneous
Markov processes and the theory of Volterra integral equations of the second kind.
In addition to the assumptions of multiagent models, we assume in the interacting agent feedback finance models that
there is a financial asset and there exists a recursive log price mechanism. The change of the types of agents is based
on the empirical distribution of the types of agents as well as the market price of the financial asset. The market
price has an influence, feedback, on the change of the internal states of agents. There are two kind of interactions
among agents: the effect of the empirical distribution of the agents' types and the feedback of market price on the
switching of an agent's type. The weak convergence criteria for timeinhomogeneous Markov processes and the theory of
nonlinear Volterra equations of second kind with semiLipschitz conditions are employed to analyze the asymptotics of
interacting agent feedback finance models. One simple example will be given to illustrate the link between the
interacting agent feedback finance models in random environments and the geometric Brownian motion of stock price
forumula suggested by Samuelson.
Time and Date: 4:005:00 p.m., Thursday, November 17, 2005
Event: Graduate Student Seminar
Speaker: Jesse Goodman, Department of Mathematics, UBC
Subject:``Conformal invariance and the restriction property''
Location: MATX 1102
Abstract: Many twodimensional random processes (including Brownian motion) are conformally
invariant: when run in two different subdomains of C, the resulting curves are related by a conformal map. Using
a blend of complex analysis and probability, recent work has classified all conformally invariant processes that
also satisfy the chordal restriction property. The talk will explain the restriction property and discuss connections
with reflected Brownian excursions, Brownian bubbles, and the SchrammLoewner evolution (SLE).
Time and Date: 4:005:00 p.m., Thursday, November 17, 2005
Event: Complex Fluids Seminar
Speaker: Speaker: Mark Jellinek, Department of Earth and Ocean Sciences, UBC
Subject:``Are Earthlike mantle plumes weird: The improbable longevity of hotspots and mantle plumes''
Location: MATH 225
Abstract: The existence, spatial distribution and style of volcanism on
terrestrial planets is an expression of their internal dynamics and
evolution. On Earth, a physical link has been proposed between
hotspots, regions with particularly persistent, localized, and high
rates of volcanism, and underlying deep mantle plumes from the
coremantle boundary. Such mantle plumes are thought to be
constructed of large spherical heads and narrow trailing conduits.
This plume model has provided a way to interpret observable phenomena
including the volcanological, petrological and geochemical evolution
of ocean island volcanoes, the relative motion of plates, continental
breakup, global heat flow and the Earth's magnetic field within the
broader framework of the thermal history of our planet. Despite the
plume model's utility the underlying dynamics giving rise to hotspots
as longlived stable features in a convecting mantle have remained
elusive. In this talk I combine results from new and published
observational, analog, theoretical and numerical studies to address
two key questions:
Why might mantle plumes in the Earth have a headtail structure?
How can mantle plumes and hotspots persist for large geological times?
I show first that the characteristic headtail structure of mantle
plumes, which is a consequence of hot upwellings having a low
viscosity, is likely a result of strong cooling of the mantle by
largescale stirring driven by plate tectonics. Second, I show that
the headtail structure of such plumes is a necessary but
insufficient condition for their longevity. Third, I summarize
seismological, geodynamic, geomagnetic and geochemical constraints on
the structure and composition of the lowermost mantle to argue that
the source regions for most deep mantle plumes contain dense, low
viscosity material within the D'' layer at the base of the Earth's
mantle. Such a layer may be composed of partial melt, outer core
material or a mixture of both (i.e. a "dense layer"). Fourth, using
results from laboratory experiments on thermochemical convection and
theoretical scaling analyses, I will argue that the longevity of
mantle plumes in the Earth is a consequence of interactions between
plate tectonics, core cooling and dense, low viscosity material
within D''. Conditions leading to Earthlike mantle plumes and
hotpsot volcanoes are highly specific and may, thus, be unique to our
own planet.
Time and Date: 2:003:00 p.m., Friday, November 18, 2005
Event: Special Information Theory Seminar
Speaker: Gadiel Seroussi, Mathematical Sciences Research Institute, Berkeley, CA
Subject:``On Universal Types''
Location: WMAX 110 (PIMS Seminar Room), 1933 West Mall, UBC
Abstract: The universal type class of a sequence x^n is defined, in analogy to the notion
underlying the classical method of types. Two sequences of the same length are said to be of the same universal
(LZ) type if and only if they yield the same dictionary (or, equivalently, parsing tree) in the incremental parsing
of Ziv and Lempel (1978). It is shown that for any finite order k, the variational distance between the kth order
empirical probability distributions of two sequences of the same universal type vanishes as the sequence length
tends to infinity. Consequently, for any k, and any kth order probability assignment, the difference between
the normalized logarithms of the probabilities assigned to two sequences of the same universal type also vanishes
asymptotically. The size of a universal type class is studied, and it is shown that its asymptotic behavior parallels
that of the conventional counterpart, with the LZ78 code length playing the role of the empirical entropy. The number
of universal types for sequences of length n is estimated, and shown to be of the form \exp((1+o(1))\gamma n/\log n)
for a well characterized constant \gamma. Algorithms for enumerating the sequences in a universal type class, and
for drawing a sequence from the class with uniform probability are described. As an application, the problem of universal
simulation of individual sequences is considered. A sequence drawn with uniform probability from the universal type
class of x^n is an optimal simulation of x^n in a well defined mathematical sense.
Time and Date: 3:00 p.m., Friday, November 18, 2005
Event: Mathematics Colloquium
Speaker: Vladimir Chernousov, University of Alberta
Subject:
``Essential dimensions of algebraic groups''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 3:004:00 p.m., Monday, November 21, 2005
Event: IAM Seminar Series
Speaker: Ulrich Horst, Department of Mathematics, UBC
Subject:``Queuing theoretic approaches to financial price fluctuations''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: We establish a central limit theorem for queuing models where the arrival and departure rates depend on stationary semiMarkov processes with heavy tailed sojourn time distributions. We show that after suitable rescaling the fluctuations around the deterministic first order approximation can be described by a fractional OrnsteinUhlenbeck process. We apply our limit theorem to model price fluctuations in financial markets with many inert investors that trade only occasionally. With our choice of scaling long range dependence emerges in financial time series. We also link investor inertia to the observed fall is the Hurst coefficient of the S&P 500 index over the late 1990s.
The talk is based on joint work with E. Bayraktar (Michigan) and R. Sircar (Princeton).
Time and Date: 3:00 p.m., Monday, November 21, 2005
Event: Algebraic Geometry Seminar
Speaker: Tonny Springer, University of Utrecht
Subject:``Some subvarieties of a compactification of a semisimple group''
Location: WMAX 110 (PIMS Seminar Room)
Abstract: An adjoint semisimple group G over an algebraically closed field has a "wonderful" compactification X (introduced by De Concini and Procesi). X is a smooth projective G\times Gvariety which contains G as an open stable subvariety, G\times G acting on G in the wellknown way. The closures in X of familiar subsets of the group G are interesting subvarieties of X. Examples of such subsets are: double cosets BwB (B a Borel subgroup) and regular conjugacy classes. In the talk I will discuss a number of recent results about the geometry of their closures.
Time and Date: 4:00 p.m., Monday, November 21, 2005
Event: Mathematics Colloquium
Speaker: Peter Walters, University of Warwick
Subject:
``Cohomology for Subshifts''
Location: MATH 104
Refreshments will be served at 3:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 12:302:00 p.m., Tuesday, November 22, 2005
Event: UBC SCAIM Seminar
Speaker: Joab Winkler, Department of Computer Science, University of Sheffield
Subject:``The stability of the effective condition number for least squares problems''
Location: MATX 1118
Abstract: The condition number of the linear algebraic equation Ax=b, where A is n x n and nonsingular, may overestimate its exact normwise condition number S(A,b), and this was the motivation for Chan and Foulser to introduce a sequence S(A,b;k), k=1,...,n, of upper bounds of S(A,b)in 1988. It is shown that although the minimum upper bound is a very good approximation to S(A,b), it is illconditioned when the equation is truly illconditioned, that is, when S(A,b) >> 1. This result is established theoretically for the normal equations that arise in least squares problems, and it is confirmed computationally by considering an example of regression using radial basis functions. It is in agreement with the result of Demmel in 1987, which states that the computation of the numerical condition of a problem is approximately as difficult as the computation of its solution.
Time and Date: 3:304:30 p.m., Tuesday, November 22, 2005
Event: Joint SFU/UBC Discrete Mathematics and Theoretical Computing Science Seminar
Speaker: Pavol Hell, School of Computing Science, SFU
Subject:``From Graph Colouring to Constraint Satisfaction: There and Back Again''
Location: SFU Campus, IRMACS Theatre
Abstract: I will discuss dichotomies in graph colouring, homomorphism, and constraint satisfaction problems, and introduce a concept of fullness of constraint satisfaction problems. When this concept is applied to graph colourings, we obtain interesting graph partition problems, which frequently arise in the study of perfect graphs. Emphasis will be on forbidden subgraph characterizations (if time permits).
Time and Date: 3:30 p.m., Tuesday, November 22, 2005
Event: DGMPPDE Seminar
Speaker: Alan Hammond, Department of Mathematics, UBC
Subject:``Moment bounds and gelation in PDE modelling coaslescence''
Location: WMAX 110 (PIMS)
Abstract: We examine the behaviour of solutions to a system of PDE (the Smoluchowski PDE), that model the aggregation of massbearing particles that diffuse and are prone to coagulate in pairs at close range. Conditions under which these solutions conserve mass for all time will be presented, along with stronger estimates, moment bounds that show that heavy particles are rare. In the case where mass conservation fails, a gelation occurs at a finite time, with particles coalescing to such a degree that some develop infinite mass. Many of the estimates have been derived both by PDE methods and by a probabilistic one. I'll give examples of each type. This is joint work with Fraydoun Rezakhanlou.
Time and Date: 2:00 p.m., Wednesday, November 23, 2005
Event: Mathematical Biology Seminar
Speaker: Fred Brauer, Department of Mathematics, UBC
Subject:``Simple pandemic models''
Location: WMAX 216 (PIMS)
Abstract: Stochastic simulation of large network models have become the standard approach to modelling epidemics and control measures, including anticipated possible pandemics. We show that simple compartmental deterministic models can give some of the predictions of such models simply and with better understanding of critical dependence on some parameters. In particular, the dependence on the initial number of infectives is critical, and this makes predictions of the amount of treatment needed for control and the number of disease cases completely unreliable. However, comparison of different control strategies is still possible.
(work joint with Julien Arino, Pauline van den Driessche, James Watmough, and Jianhong Wu).
Time and Date: 3:30 p.m., Wednesday, November 23, 2005
Event: Algebra Topology Seminar
Speaker: Tonny Springer, University of Utrecht
Subject:``Some subvarieties of a compactification of a semisimple group II''
Location: WMAX 110, Note: This is a continuation of Monday's Algebraic Geometry Seminar.
Time and Date: 3:304:30 p.m., Wednesday, November 23, 2005
Event: Probability Seminar
Speaker: Codina Cotar, Department of Mathematics, UBC
Subject:``Edge reinforced random walk as a random walk in random environment''
Location: WMAX 216
Abstract: We consider linear edge reinforced random walk on a finite graph. This was
studied by S. Rolles and M.S.Keane, who developed the so called "magic
formula", expressing a linear edge reinforced random walk as a random walk
in a random environment.
By using properties of the gamme function, a new equivalent formula is
developed.
Time and Date: 4:00 p.m., Wednesday, November 23, 2005
Event: IAM StudentFaculty Seminar
Speaker: Miguel Angel MoyersGonzalez, Department of Mathematics, UBC
Subject:``Transient effects in oilfield cementing flows''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: A twodimensional evolution model for displacement flows occurring
in the primary cementing of an oil well is presented. This process involves
displacement of a sequence of nonNewtonian fluids along
a narrow eccentric annulus. It has been shown that for certain
rheological and physical parameters of the fluids, the
displacement front will advance much faster on the wide side of
the annulus than on the narrow side. In extreme cases the
displacement front does not advance at all on the narrow side of
the annulus and a static mud channel results as the finger
advances up the wide side. We consider whether the interface of a
progressively advancing finger will remain stable to small
perturbations and also investigate how a mud channel might be
removed by pulsation of the flow rate, which is sometimes used in
the cementing industry.
Time and Date: 3:003:50 p.m., Thursday, November 24, 2005
Event: SFU/UBC Number Theory Seminar at UBC
Speaker: Yoonjin Lee, SFU
Subject:``The structure of the class groups of global function fields of any unit rank''
Location: UBC Campus, WMAX 110 (PIMS Seminar Room), 1933 West Mall
Abstract: The problem of determining the structure of the class group dates back to Gauss. In this talk we discuss the structure of the class groups of global function fields. Let F be a finite field and T a transcendental element over F. We show an explicit method of constructing, for positive integers m,n, and r with 0 â r â m1, infinitely many global function fields K of degree m over F(T) such that K has a given unit rank r and the ideal class group of K contains a subgroup isomorphic to (Z/nZ)^{mr}.
Time and Date: 4:005:00 p.m., Thursday, November 24, 2005
Event: PIMSMITACS Math Finance Seminar
Speaker: Tahir Choulli, Department of Mathematical & Statistical Sciences, University of Alberta
Subject:``Minimal Hellinger martingale measures of order q''
Location: WMAX 216
Abstract: In my talk I will propose an extension of the minimal Hellinger martingale measure (MHM hereafter) concept to any order q\not=1 and to the general semimartingale framework. This extension allows us to provide a unified formulation for the minimal martingale measure of F\"ollmeer and Schweizer (here q=2), the minimal Hellinger martingale measure of Grandits (here q=1/2), and the minimal distance martingale measure when the utility is logarithmic (here q=0). Under some mild conditions of integrability and arbitrage, we show the existence of the MHM measure of order q, and we describe it explicitly in terms of pointwise equations
in \RR^d. Application to the maximization of expected power utility at stopping times with implied liability or endowment is given. We describe an optimal investment that is robust with respect to the investor's lifetime (which could be certain or announced at birth). Finally the main results of the paper are illustrated for the discretetime market models, where a relationship between this optimal martingale measure and a dynamic risk measure is established as well.
This talk is based on a joint paper with Christophe Stricker and Jia Li.
Time and Date: 4:005:00 p.m., Thursday, November 24, 2005
Event: Complex Fluids Seminar
Speaker: Dana Grecov, Department of Mechanical Engineering, UBC
Subject:``Modeling Microstructural Processes in Liquid Crystalline Flows''
Location: MATH 225
Abstract: The orientational order of liquid crystal materials offers a unique pathway to
create new nano and microstructures with unique optical, electromagnetic, and
mechanical properties. Nematic liquid crystalline materials are textured,
anisotropic, viscoelastic materials. Their mechanical behavior is greatly
influenced by the presence of textures, or spatial distribution of topological
defects. We present a multiscale theory and simulation of hydrodynamic texture
formation to provide fundamental principles for control and optimization of
structures in liquid crystal materials. We characterize the relation between
rheological functions and textural transformations of flowaligning liquid
crystalline materials subjected to shear startup flow. Defects reduce stress
so that when defects leave the system, the shear stress increases. Simulated
textural transformations show that smooth staircase stress growth is the result
of defect annihilation processes. The nonmonotonic stress growth is consistent
with experimental observations. Simulated textures provide specific important
knowledge to the understanding of the rheology of textured liquid crystalline
materials.
Time and Date: 4:105:00 p.m., Thursday, November 24, 2005
Event: SFU/UBC Number Theory Seminar at UBC
Speaker: Stephen Choi, SFU
Subject:``Why Lehmer's conjecture is so difficult''
Location: UBC Campus, WMAX 110 (PIMS Seminar Room), 1933 West Mall
Abstract: We compute asymptotic formulas for mean values of Mahler's measure and the Lpnorms of several classes of polynomials with restricted coefficients and bounded degree. We study the unimodular polynomials with complex coefficients of modulus 1, the Littlewood polynomials with {1,1} coefficients, the height1 polynomials with {1,0,1} coefficients, and their restrictions to reciprocal polynomials. We show for instance that both the geometric mean and the arithmetic mean of Mahler's measure of the unimodular polynomials with degree n1 approach e^{Î³/2}n^{1/2} as n grows large, and that this same result holds for the Littlewood polynomials. Moreover, we prove that the normalized measure or Lpnorm of a polynomial in one of these families lies arbitrarily close to the corresponding mean value with probability approaching 1 as the degree grows large.
Time and Date: 3:00 p.m., Friday, November 25, 2005
Event: Mathematics Colloquium
Speaker: Ivar Ekeland, PIMS, UBC
Subject:
``Nuts, bolts, and markets''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 3:004:00 p.m., Monday, November 28, 2005
Event: IAM Seminar Series
Speaker: James J. Feng, Department of Mathematics and the Department of Chemical and Biological Engineering, UBC
Subject:``Recent Adventures on Interfaces of Simple and Complex Fluids''
Location: Room 301, Leonard S. Klinck Bldg.
Abstract: I will report recent results from our group on experimental and computational studies of interfacial dynamics of Newtonian and viscoelastic fluids. The experimental work has centered on the coalescence between a drop and a fluidfluid interface, where a phenomenon known as 'partial coalescence' takes place within proper ranges of the Ohnesorge number. We have identify the mechanisms governing this process for Newtonian and polymeric liquids. On the numerical side, we have successfully reproduced the experimental observations of partial coalescence. In addition, I will also discuss simulations of the formation and dispersion of droplets in microfluidic channels.
Time and Date: 3:00 p.m., Monday, November 28, 2005
Event: Algebraic Geometry Seminar
Speaker: Kiumars Kaveh, UBC
Subject:``Canonical bases and toric degeneration of flag and spherical varieties''
Location: WMAX 110 (PIMS Seminar Room)
Abstract: I will briefly introduce KashiwaraLutzig canonical basis and its string parametrization due to Littleman, Bernstein and Zelevinsky. I then show how the combinatorics of string parametrization can be used to prove that the homogeneous coordinate ring of a flag variety has a socalled SAGBI basis. This will imply that a flag variety can be flatly degenerated to a toric variety. This result extends to the more general case of spherical varieties.
Time and Date: 3:30 p.m., Tuesday, November 29, 2005
Event: DGMPPDE Seminar
Speaker: Claudio Fernandez, Pontificia Universidad Catolica de Chile
Subject:``Absence of embedded eigenvalues for perturbed Hamiltonians''
Location: WMAX 110 (PIMS)
Abstract: We shall show how to use a technique, based on commutator estimates, to prove that the propagator U(t,0) for a selfadjoint operator H(t)=H_0+V(t), has no eigenvalues, with adequate conditions on the potential V.
Secondly, we consider the Stark magnetic Hamiltonian, H(\mu ,\epsilon )=(D_xuy)^2+D_y^2+\epsilon x+V(x,y), on the Hilbert space L^2(\mathbb R^2). We show that if the potential V satisfies some mild regularity conditions and it is sufficiently decaying at infinity, then the operator H has no eigenvalues.
Time and Date: 2:00 p.m., Wednesday, November 30, 2005
Event: Mathematical Biology Seminar
Speaker: Muhammad Arshad Chaudhry, Michael Smith Laboratories, UBC
Subject:``Influence of Culture pH and Osmolality on the Maintenance of Pluripotentiality of Murine Embryonic Stem Cells''
Location: WMAX 216 (PIMS)
Abstract: The clinical realization of stem cells based gene and tissue
regeneration therapies depends on the development of consistent, robust and scalable processes
to expand their numbers without compromising their developmental potential. Murine embryonic
stem (ES) cells provide a practical model for stem cell culture process research as they can
be readily obtained at relatively high numbers and purities. Conventional ES cultures require
daily medium exchange and an understanding of their environmental tolerance ranges is still
lacking. We have now begun to explore these using a functional assay (Embryoid body, EB,
formation) to quantify the integrity of an ES cell line, R1, exposed to various culture
stresses. Based on the EB formation assay, culture environment strongly influences the
developmental potential of two ES cell lines, R1 and EFC. A doseresponse analysis of R1 cells
exposed to various medium pH and osmolalities was carried out and revealed that within 48 h,
the yield of EBs was ~ 3fold decreased (p<0.05) when R1 cells were cultured in pH 7.0 or 400 mOsm/kg
osmolality medium (compared to a pH of 7.3 and 300 mOsm/kg osmolality). This was due to both
a relative and absolute decreases in the rate of EBforming cell expansion. These studies
provide guidance in determining the optimal culture conditions and environmental tolerances
for stem cell bioprocess research and development.
Time and Date: 3:30 p.m., Wednesday, November 30, 2005
Event: Algebra Topology Seminar
Speaker: Alejandro Adem, PIMS & UBC
Subject:``Products in the Cohomology and Ktheory of Orbifold''
Location: WMAX 110
Abstract: We will discuss products in the cohomology and Ktheory of orbifolds, as well as a twisted version for certain cocycles.
Time and Date: 4:00 p.m., Wednesday, November 30, 2005
Event: IAM StudentFaculty Seminar
Speaker: Livio Gibelli, Postdoctoral Fellow, Department of Mathematics, Milan Polytechnic, Italy
Subject:``Elements of kinetic theory"
Location: LSK 301
Abstract: The talk will give a brief overview of the basic elements of the kinetic
theory of gases. The purpose of kinetic theory is to model the time
evolution of a collection of particles. The particles may be entirely
different objects depending on the physical situation. For instance, the
particles are molecules in a neutral gas, electrons and ions in a plasma,
stars in stellar dynamics, galaxies or even clusters of galaxies in
cosmological problems. Mathematical models of particle systems are most
frequently described by kinetic or fluid equations. The connection between
the two approaches will be stressed. The time evolution of the system is
determined by the nature of interactions between the particles. The cases
in which the driving mechanisms are collisions (the Boltzmann equation)
and interaction through electromagnetic fields (the VlasovMaxwell system)
will be briefly discussed.
Time and Date: 3:30 p.m., Thursday, December 1, 2005
Event: DGMPPDE Seminar
Speaker: Andrew Comech, Texas A & M University
Subject:``Global attractor for the KleinGordon equation with a nonlinearity supported at a point''
Location: WMAX 110 (PIMS)
Abstract: We consider the longtime asymptotics of all finite energy solutions to the KleinGordon equation in one dimension, with the nonlinearity concentrated at a point. Our main result is that the attracting set of any finite energy solution consists of ``nonlinear eigenfunctions'', also known as solitary or standing waves. The problem is inspired by Bohr's postulate on quantum transitions and Schroedinger's identification of the quantum stationary states to the eigenfunctions of the coupled MaxwellSchroedinger or MaxwellDirac equations. This is a joint work with Alexander Komech, Vienna University.
Time and Date: 4:005:00 p.m., Thursday, December 1, 2005
Event: Graduate Student Seminar
Speaker: Mat Rogers, Department of Mathematics, UBC
Subject:``A brief introduction to Mahler Measure''
Location: MATX 1102
Abstract: In this talk I will give a brief introduction to Mahler
measure, and I will discuss a few of my recent results. Recall that the Mahler measure
of a ndimensional polynomial, P(x1,...xn), is defined by the ndimensional integral,
m(P(x1,...,xn))=\int\logP(z1,...zn)/(z1*...*zn) dz1...dzn, where the path of integration
is taken over T^n.
When n>=2, we can find identities expressing Mahler measures in terms of Lfunctions.
For example, I recently showed that, m(x+(1+x)^2+(1+x+y)^2 z)=28/5*Zeta(3)/Pi^2+Log(Phi),
where Phi=(1+5^(1/2))/2 is the goldenratio, and Zeta(3)=1+1/2^3+1/3^3.... I will discuss
several results of this type.
Time and Date: 4:00 p.m., Thursday, December 1, 2005
Event: Complex Fluids Seminar
Speaker: Isaias Ochoa, Dept. of Chemical Engineering, UBC
Subject:``Paste extrusion of Polytetrafluoroethylene (PTEE) fine powder resin: The effects of the processing aid physical properties''
Location: MATH 225
Abstract: The rheological properties of a number of polytetrafluoroethylene (PTFE) pastes were studied relevant to paste extrusion process. The effects of the physical properties of lubricants and the geometrical characteristics of the extrusion die on the performing, extrusion pressure and mechanical properties of the final extrudates were also examined. A number of lubricants were characterized in terms of both flow and surface properties and identified as suitable for the paste extrusion of polytetrafluoroethylene (PTFE). The flow and surface properties of some lubricants were altered to study their relative effects on preforming and extrusion of PTFE paste. Based on this study, it was concluded that preforming quality increases with increase of lubricant viscosity and with improvement in the wettability characteristics of the lubricant with PTFE. The effects of the lubricant physical properties on the processing of polytetrafluoroethylene (PTFE) fine powder resins were also studied. It was found that the wettability (surface tension) and the viscosity of the lubricant play a significant role in the process as they strongly affect the pressure needed to extrude the PTFE pastes. These effects of the physical properties on the extrusion pressure influence significantly the mechanical properties of the final extrudates since the degree of fibrillation is strongly related to the extrusion pressure. The effects of die geometry as well as the extrusion temperatureon on extrusion pressure and mechanical properties of extrudates were also assessed in order to determine the geometrical characteristics and operation conditions for the optimization of the process. Finally, rheological characterization studies of the paste and the extrudates were performed in an attempt to clarify the behaviour of such an amazing material.
Time and Date: 3:00 p.m., Friday, December 2, 2005
Event: Mathematics Colloquium
Speaker: Maciej Zworski, UC Berkeley
Subject:
``Counting states in wave mechanics''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (MATX 1115, Math Lounge).
Time and Date: 3:004:00 p.m., Monday, December 5, 2006
Event: Algebraic Geometry Seminar
Speaker: Patrick Brosnan, Department of Mathematics, UBC
Subject:``Jumps in the height of the HainReed biextension line bundle over the moduli space of curves''
Location: MATX 1102
Abstract: Using Hodge theory, Richard Hain and David Reed have defined a natural metrized line bundle B on the moduli space of curves. Hain and Reed showed that B extends with its metric to the moduli space of stable curves with compact type. However, Greg Pearlstein and I have shown that the metric of B is singular on certain strata of noncompact type in the boundary of the moduli space of stable curve. Our measure of singularity of the metric boils down to an invariant the degeneration of a variation of mixed Hodge structure which we call the jump.
I plan to explain B, it's metric and our calculation of the jump.
Time and Date: 3:304:30 p.m., Monday, December 5, 2005
Event: Probability Seminar **Cancelled**
Speaker: Burgess Davis, Purdue University
Subject:``Continuous time vertex reinforced random walk''
Location: WMAX 216 (PIMS)
Abstract: I will talk about joint work with Stas Volkov concerning a nearest neighbor random walk on graphs. On the integer lattice the walk is defined as follows. Initially the weight of each integer is one. The walk jumps to each of its neighbors at a rate proportional to the weight of that neighbor. The weight of an integer at time t is the time up to t that the walk has spent at the neighbor. So for example, the first jump is equally likely to be to either neighbor and the time T before this jump is exponential rate 2, while the second jump is exponential rate 2+a if T=a. The integers visited by this walk up to time t are asymptotically the interval (clogt, clogt) where c is explicitly given. On some regular trees the walk goes to infinity while on others it visits every vertex.
Time and Date: 12:302:00 p.m., Tuesday, December 6, 2005
Event: UBC SCAIM Seminar
Speaker: Wayne Hayes, Department of Computer Science, UC Irvine
Subject:``From Butterflies to Galaxies: reliable simulation of chaotic systems''
Location: CS X736 Note: This is an alternate location (7th floor of new CS building).
Abstract: The "Butterfly Effect" refers to the idea that a butterfly flapping
its wings in Hawaii can affect the weather over Vancouver a few weeks
later. The Butterfy Effect is an example of "sensitive dependence on
small changes", which is exhibited by many nonlinear dynamical
systems from integrated circuits to galaxies. When such systems are
simulated on a computer, this sensitivity causes small numerical
errors to become exponentially magnified, leading to the possibility
that trajectories of such simulations are the result of nothing but
magnified noise. To justify the reliability of such simulations, we
turn to the study of "shadowing". A "shadow" is an exact trajectory
that stays close to a numerical trajectory for a long time, even in
the face of sensitive dependence. From the standpoint of physics, a
numerical trajectory that has a shadow can be viewed as an
experimental observation of that shadow, which means that the
dynamics observed in the simulation are real. This is a very strong
statement of simulation reliability. However, verifying the existence
of a shadow formally takes time O(N^3), where N is the number of
components in the system. In this talk I will outline how I
demonstrated the existence of shadows of galaxy simulations in which
N=10^8.
Time and Date: 3:30 p.m., Tuesday, December 6, 2005
Event: DGMPPDE Seminar
Speaker: Alexei Cheviakov, Department of Mathematics, UBC
Subject:``Framework for potential systems and nonlocal symmetries: Algorithmic approach''
Location: WMAX 110 (PIMS)
Abstract: For a given PDE system, one can construct extended hierarchies ("trees") of nonlocallyrelated PDE systems. Each system in an extended tree is equivalent, in the sense that the solution set for any system in a tree can be found from the solution set for any other system in the tree. Due to the equivalence of solution sets, any coordinateindependent method of analysis (qualitative, numerical, perturbation, etc.) can be applied to any system within the tree, and may yield simpler computations and new results that cannot be obtained when the method is directly applied to the given system. Nonlocal symmetries and new local and nonlocal conservation laws for a given PDE system can arise from any system in its extended tree.
We construct extended trees for the systems of Planar Gas Dynamics and Nonlinear Telegraph equations. Using the described framework, we demonstrate a direct relation between Eulerian and Lagrangian descriptions of gas dynamics, and find new families of conservation laws and new nonlocal symmetries.
The presented research was done in collaboration with George Bluman (UBC).
Time and Date: 3:304:20 p.m., Tuesday, December 6, 2005
Event: Joint Discrete Mathematics  Theoretical Computing Science UBC/SFU Seminar
Speaker: David S. Gunderson, University of Manitoba
Subject:``Sumsets, primes, and combinatorics''
Location: SFU Campus, ASB 10900, IRMACS Theatre
Abstract: If A and B are sets of numbers, the set A+B=\{a+b:a\in A, b\in B\} is called a sumset. Many questions in combinatorial number theory focus on sumsets and primes or prime factorization. For example, one might ask how large can two sets be so that their sumset consists only of primes? (When A=\{1,7\} and B=\{4,6\}, the sumset A+B consists only of primes.)
Some questions regarding sumsets and primes have been answered using only the pigeonhole principle, Ramsey theory, or extremal graph theorywith no properties of primes being used!
The main theorem in this talk regards the parity of the number of factors in A, B, and A+B. Let \Omega(n) denote the number of prime factors (not necessarily distinct) of n. In 1999, Rivat, S\'ark\"ozy and Stewart proved a result regarding maximal cardinalities of sets A, B
\subset\{1,\ldots,N\} so that for every a\in A and b\in B, \Omega(a+b) is even.
In joint work with Christian Elsholtz (Royal Holloway, University of London)
the RivatS\'ark\"ozyStewart theorem is strengthened in three ways:
(1) The role of Liouville \lambdafunction, given by \lambda(n)=(1)^{\Omega(n)}, is generalized to all nonconstant completely multiplicative functions f from the natural numbers to \{1,1\}.
(2) Their results are also extended to all possible parities of \Omega on A, B, and A+ B, and,
(3) in each case, `many' such pairs (A,B) exist.
Time and Date: 2:00 p.m., Wednesday, December 7, 2005
Event: Mathematical Biology Seminar
Speaker: Anmar Khadra, Department of Mathematics, UBC
Subject:``Modeling the Pulsatile and Synchronized Behaviour of GnRH Neurons''
Location: WMAX 216
Abstract: The hypothalamic GnRH (Gonadotropin Releasing Hormone) decapeptide is essential for reproductive processes in vertebrates. GnRH plays key roles in the onset and progression of reproductive maturation, and regulation of hormonal changes that occur during menstrual and estrous cycle. It mediates the reproductive system responses to seasonal or diurnal cues. In primates, GnRH is secreted from synchronized GnRH neurons in a pulsatile and episodic manner in the median eminence, e.g., in humans, the hormone is released approximately every 60 mins. This pulsatile and episodic pattern is crucial for normal reproductive function. The underlying mechanism of the GnRH pulse generator that is responsible for the episodic secretion of GnRH has yet to be established. It is clear, however, that GnRH neurons have an intrinsic capacity for the generation of pulsatile neurosecretion. Recent experiments revealed important details of the molecular events underlying the GnRH pulsatility.
It has been shown that GnRH neurons express GnRH receptors allowing GnRH to exert an autocrine action on them. Krsmanovic et al., proposed a mechanism describing this autocrine effect via Calcium and cAMP. In this talk we will present a mathematical model which reflects the properties of the proposed mechanism. Furthermore, we illustrate how this hormone can act as an agent or a "diffusible mediator" that is responsible for coupling the GnRH neurons to generate synchronized release of itself. We also show the robustness of synchronization to variations in the properties of the GnRH neurons.
Time and Date: 3:30 p.m., Wednesday, December 7, 2005
Event: Algebra Topology Seminar
Speaker: Ian Hambleton, McMaster University
Subject:``Finite groups acting freely on products on spheres''
Location: WMAX 110
Abstract: We will present some details of new methods and results about which finite groups can act freely and smoothly on a product of spheres.
Time and Date: 3:003:50 p.m., Thursday, December 8, 2005
Event: SFU/UBC Number Theory Seminar at SFU
Speaker: Chris Sinclair, PIMS, SFU, UBC
Subject:``Determinants, Pfaffians and Volumes of Polynomials''
Location: SFU Campus, Room ASB 10900
Abstract: I will outline a method for computing certain volumes of polynomials of interest to number theorists, random matrix theorists, and physicists.
Time and Date: 4:105:00 p.m., Thursday, December 8, 2005
Event: SFU/UBC Number Theory Seminar at SFU
Speaker: Mat Rogers, Department of Mathematics, UBC
Subject:``Multivariable Mahler measures and related integrals''
Location: SFU Campus, Room ASB 10900
Time and Date: 3:00 p.m., Friday, December 9, 2005
Event: Mathematics Colloquium
Speaker: Ian Hambleton, McMaster University
Subject:
``Groups and Geometry''
Location: WMAX 110 (PIMS Seminar Room)
Refreshments will be served at 2:45 p.m. (WMAX PIMS Lounge).
Time and Date: 11:00 a.m., Wednesday, December 14, 2005
Event: Algebra Topology Seminar
Speaker: Genevieve Walsh, U of Texas, Austin
Subject:``Surfaces in finite covers and the group determinant''
Location: WMAX 110
Abstract: We show that infinitely many fillings of any onecusped
hyperbolic threemanifold are virtually Haken. The main tool is a symmetrized version
of the group determinant, as studied by Frobenius and Dedekind. I will explain what the
group determinant is, and how it relates to this problem via the representation theory
of finite groups. This is joint work with Daryl Cooper (UCSB).
Time and Date: 2:003:00 p.m., Wednesday, December 14, 2005
Event: Mathematics Colloquium
Speaker: Alexander Jones, University of Toronto
Subject:
``Locus theorems in ancient Greek geometry''
Location: WMAX 110 (PIMS Seminar Room)
Refreshments will be served at 1:45 p.m. (PIMS Lounge).
Time and Date: 3:30 p.m., Wednesday, December 14, 2005
Event: Algebra Topology Seminar
Speaker: Victor Nunez, CIMAT
Subject:``Universal Montesinos knots''
Location: WMAX 110
Abstract: An interesting way of constructing 3manifolds is through the study of branched coverings and universal knots. Montesinos knots were, until recently, untractable in questions about universality.
We explore the theory of universal knots, and review some known results. Using these and some new points of view, we show universality of many Montesinos knots.
Time and Date: 11:00 a.m., Friday, December 16, 2005
Event: Algebra Topology Seminar
Speaker: Rick Jardine, UWO
Subject:``Cocycle categories and gerbes''
Location: WMAX 110
Abstract: Cocycle categories are ubiquitous in homotopy theory, and their sets of path components represent morphisms in a large family of homotopy categories. The cocycle category approach is a flexible tool for demonstrating homotopy classifications results for equivalence classes of objects with structure. This approach can be used, in particular, to give homotopy classification results for locally connected stacks (aka. gerbes).
It's not as scary as it sounds.
Time and Date: 3:004:00 p.m., Friday, December 16, 2005
Event: Mathematics Colloquium
Speaker: Ramesh Sreekantan, Tata Institute
Subject:
``Drinfeld Modular Curves and special values of Lfunctions''
Location: MATX 1100
Refreshments will be served at 2:45 p.m. (Math Lounge).
