Print Friendly printer friendly
 Events
UBC Math
Fri 30 Sep 2016, 3:00pm
Department Colloquium
ESB 2012
UBC Mathematics and PIMS Faculty Award Colloquium -- On the local Langlands conjectures
ESB 2012
Fri 30 Sep 2016, 3:00pm-4:00pm

Abstract

The Langlands program, initiated in the 1960s, is a set of conjectures predicting a unification of number theory and the representation theory of groups. More precisely, the Langlands correspondence provides a way to interpret results in number theory in terms of group theory, and vice versa.

In this talk we sketch a few aspects of the local Langlands correspondence using elementary examples. We then comment on some questions raised by the emerging "mod p" Langlands program.
hide
Jessica Bosch
Department of Computer Science, UBC
Tue 4 Oct 2016, 12:30pm
Scientific Computation and Applied & Industrial Mathematics
ESB 4133 (PIMS Lounge)
Fast Iterative Solvers for Cahn-Hilliard Problems
ESB 4133 (PIMS Lounge)
Tue 4 Oct 2016, 12:30pm-1:30pm

Abstract

The Cahn-Hilliard equation models the motion of interfaces between several phases. The underlying energy functional includes a potential for which different types were proposed in the literature. We consider smooth and nonsmooth potentials with a focus on the latter. In the nonsmooth case, we apply a function space-based algorithm, which combines a Moreau-Yosida regularization technique with a semismooth Newton method. We apply classical finite element methods to discretize the problems in space. At the heart of our method lies the solution of large and sparse fully discrete systems of linear equations. Block preconditioners using effective Schur complement approximations are presented. For the smooth systems, we derive optimal preconditioners, which are proven to be robust with respect to crucial model parameters. Further, we prove that the use of the same preconditioners give poor approximations for the nonsmooth formulations. The preconditioners we present for the nonsmooth problems incorporate the regularization terms. Extensive numerical experiments show an outstanding behavior of our developed preconditioners. Our strategy applies to different Cahn-Hilliard problems including phase separation and coarsening processes, image inpainting, and two-phase flows. 
hide
University of California at Irvine
Tue 4 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
On the first eigenvalue estimate for sub-Laplacian and Kohn Laplacian and Rigidity Theorems on pseudo-Hermitian CR manifolds
ESB 2012
Tue 4 Oct 2016, 3:30pm-4:30pm

Abstract

 In this talk, I will present  a CR-version of Lichnerowicz--Obata type theorem in a closed pseudo-Hermitian CR manifolds. It includes the lower bound estimates for the first positive eigenvalue for the both sub-Laplacian and Kohn Laplacian. I will also provide Obata type theorem associated to the sub-Laplacian and Kohn Laplacian on a closed pseudo-Hermitian manifold. As an application, we give some rigidity theorem when lower bound of eigenvalue is achieved. This is based on a joint work with X. Wang and a joint work with Duong N. Son and Wang. I will also talk about some ongoing work in this topic.
hide
Santiago Salazar
UBC
Tue 4 Oct 2016, 4:00pm
Discrete Math Seminar
ESB 4127
Forbidden Berge hypergraphs
ESB 4127
Tue 4 Oct 2016, 4:00pm-5:00pm

Abstract

 Given two matrices A,B we say that A is a Berge hypergraph of B if there is a submatrix of B, say matrix D, and a row and column permutation of A, say matrix C, so that C<=D. Define Av(m,F) to be the set of all m-rowed (0,1)-matrices with no repeated columns and no Berge hypergraph F. Define Bh(m,F) to be the maximum, over all matrices A in Av(m,F), of the number of columns of A. We are interested in determining the asymptotic growth of Bh(m,F) for specific F. We show some techniques we can use to this end and mention the general results determined for F with 5 or fewer rows. We also show that if F is the vertex-edge incidence matrix of a tree then bh(m,F) has a linear bound. When F is the vertex-edge (s+t)x(st) incidence matrix of the bipartite graph K_{s,t} we show that finding Bh(m,F) relates to determining ex(m,K_r,K_{s,t} ), the maximum number of complete subgraphs K_r in a m-vertex graph avoiding K_{s,t} as a subgraph. Recent papers by Alon and others have solved some cases.
hide
Cindy Greenwood
UBC
Wed 5 Oct 2016, 1:45pm
Mathematical Biology Seminar
PIMS (ESB 4th floor)
Hidden Patterns Revealed by Noise: semi-arid vegetation patterns
PIMS (ESB 4th floor)
Wed 5 Oct 2016, 1:45pm-2:45pm

Abstract

A deterministic model may sometimes seem to be a good description of the dynamics of an observed system but may have a long-term stable constant limit, whereas observations of the system itself show a noisy pattern. An example is semi-arid vegetation patterns. Adding noise to the model may well reveal the pattern. In this talk I show some photos, talk about some math, and show some simulations. This is not a magic show.
hide
UBC Computer Science and PIMS
Wed 5 Oct 2016, 3:00pm
Probability Seminar
ESB 2012
On longest paths and diameter in random Apollonian networks
ESB 2012
Wed 5 Oct 2016, 3:00pm-4:00pm

Abstract

Consider the following iterative construction of a random planar triangulation. Start with a triangle embedded in the plane. In each step, choose a bounded face uniformly at random, add a vertex inside that face and join it to the vertices of the face. After n – 3 steps, we obtain a random triangulated plane graph with n vertices, which is called a Random Apollonian Network (RAN). See http://www.math.cmu.edu/~ctsourak/ran.html for an example.

We prove that the diameter of a RAN is asymptotic to c log(n) in probability, where c ≈ 1.668 is the solution of an explicit equation. The proof adapts a technique of Broutin and Devroye for estimating the height of random trees.

We also prove that there exists a fixed s<1, such that eventually every self-avoiding walk in this graph has length less than n^s, which verifies a conjecture of Cooper and Frieze. Using a similar technique, we show that if r < d are fixed constants, then every r-ary subtree of a random d-ary recursive tree on n vertices has less than n^b vertices, for some b=b(d,r)<1.

Based on joint work with A. Collevecchio, E. Ebrahimzadeh, L. Farczadi, P. Gao, C. Sato, N. Wormald, and J. Zung.
hide
Western Washington University
Wed 5 Oct 2016, 3:00pm
Harmonic Analysis Seminar
MATH 126
On probabilistic Strichartz estimates for the NLS
MATH 126
Wed 5 Oct 2016, 3:00pm-4:00pm

Abstract

We will begin by briefly discussing the non-linear Schroedinger (NLS) equation and the corresponding classical Strichartz estimates. We will then introduce a so-called Wiener randomization of initial data and indicate how it leads to an improvement of the classical Strichartz estimates. As a toy application, we will show how, in contrast with the deterministic case, the energy-critical cubic NLS in four dimensions is almost surely well-posed with respect to randomized initial data below the energy space. This is a joint work with Tadahiro Oh (University of Edinburgh) and Oana Pocovnicu (Heriot-Watt University).
hide
University of Southern California
Wed 5 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
A new proof of the decomposition theorem
ESB 4133 (PIMS Lounge)
Wed 5 Oct 2016, 3:15pm-4:15pm

Abstract

In this talk, we will discuss a new proof of the decomposition theorem of Beilinson, Bernstein, Deligne and Gabber for semi-simple perverse sheaves of geometric origin on complex algebraic varieties. This proof follows from rather formal considerations of higher algebra, stable motivic homotopy theory and Grothendieck's six functors, avoiding both the positive-characteristic methods of the original proof, and the delicate analysis of degenerations of mixed Hodge structures involved in M. Saito's proof.
 
hide
Laure Saint-Raymond
Harvard University, ENS
Fri 7 Oct 2016, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium--Propagation of chaos and irreversibility in gas dynamics
ESB 2012
Fri 7 Oct 2016, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments (A light reception) are served in ESB 4133 from 2:30pm-3:00pm before the colloquium.
hide
Tobias Huxol
UBC
Tue 11 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 11 Oct 2016, 3:30pm-4:30pm

Abstract

 
hide
UBC Math
Wed 12 Oct 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 12 Oct 2016, 3:00pm-4:00pm

Abstract

 
hide
UBC
Wed 12 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
TBA, part I
ESB 4133 (PIMS Lounge)
Wed 12 Oct 2016, 3:15pm-4:15pm

Abstract

 
hide
Frank Sotille
TAMU
Thu 13 Oct 2016, 4:00pm
Discrete Math Seminar
Math 126
Math 126
Thu 13 Oct 2016, 4:00pm-5:00am

Abstract


hide
UBC Math
Fri 14 Oct 2016, 3:00pm
Department Colloquium
Math Annex 1100
TBA
Math Annex 1100
Fri 14 Oct 2016, 3:00pm-4:00pm

Abstract


hide
UBC
Mon 17 Oct 2016, 3:00pm
Harmonic Analysis Seminar
MATH 126
Large Sets Avoiding Patterns
MATH 126
Mon 17 Oct 2016, 3:00pm-4:00pm

Abstract

 
hide
Saikat Mazumdar
UBC
Tue 18 Oct 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 18 Oct 2016, 3:30pm-4:30am

Abstract


hide
Gizem Karaali
Pomona College
Tue 18 Oct 2016, 4:00pm
Discrete Math Seminar
ESB 4127
ESB 4127
Tue 18 Oct 2016, 4:00pm-5:00pm

Abstract


hide
University of Washington
Wed 19 Oct 2016, 3:00pm
Probability Seminar
ESB 2012
Extremal conformal metrics, spectral geometry, and distributional limits of graphs
ESB 2012
Wed 19 Oct 2016, 3:00pm-4:00pm

Abstract

I will talk about an intrinsic approach to uniformization of a graph's geometry based on extremal discrete metrics.  This method allows one to generalize known results about planar graphs that rely heavily on the theory of circle packings, and to obtain new information even for well-studied models of planar graphs like the uniform infinite triangulation (UIPT) and quadrangulation (UIPQ).
 
It yields a short proof of Benjamini and Schramm's result that a distributional limit of bounded-degree planar graphs is almost surely recurrent.  The same argument resolves a 2001 conjecture of those authors since it works also for H-minor-free graphs (and, in fact, a substantial generalization known as region intersection graphs).
 
Gurel-Gurevich and Nachmias recently solved a central open problem by showing that UIPT and UIPQ are almost surely recurrent.  By combining extremal discrete metrics with methods from spectral geometry, I will present a new proof of this fact that also gives explicit control on divergence of the Green function.  If g(x, T) denotes the number of returns to the root at time T, we show that almost surely (over the choice of the random rooted graph), g(x,T) grows asymptotically at least as fast as log log T.  This is a consequence of a general result that holds for any distributional limit of H-minor-free graphs and provides lower bounds on return probabilities based on the tails of the degree distribution of the root.
 
Finally, I will discuss extensions to general graphs and, in particular, give a characterization of the almost sure spectral dimension of a distributional limit in terms of the "conformal growth rate" of any sequence that approaches the limit graph.  This has consequences for graphs that can be sphere-packed in R^d for d > 2.
hide
UBC
Wed 19 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
TBA, part II
ESB 4133 (PIMS Lounge)
Wed 19 Oct 2016, 3:15pm-4:15pm

Abstract

 
hide
UBC Math
Fri 21 Oct 2016, 3:00pm
Department Colloquium
Math Annex 1100
TBA
Math Annex 1100
Fri 21 Oct 2016, 3:00pm-4:00pm

Abstract


hide
Alessandro Marinelli
UBC
Mon 24 Oct 2016, 3:00pm
Harmonic Analysis Seminar
Math 126
Math 126
Mon 24 Oct 2016, 3:00pm-4:00pm

Abstract

 
hide
Brian Chan
UBC
Tue 25 Oct 2016, 4:00pm
Discrete Math Seminar
ESB 4127
ESB 4127
Tue 25 Oct 2016, 4:00pm-5:00pm

Abstract

 
hide
TBA
Wed 26 Oct 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 26 Oct 2016, 3:00pm-4:00pm

Abstract

 TBA
hide
NTNU Norwegian University of Science and Technology
Wed 26 Oct 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
TBA
ESB 4133 (PIMS Lounge)
Wed 26 Oct 2016, 3:15pm-10:00am

Abstract


hide
McGill University
Fri 28 Oct 2016, 3:00pm
Department Colloquium
ESB 2012
CRM-Fields-PIMS Award Lecture: TBA
ESB 2012
Fri 28 Oct 2016, 3:00pm-4:00pm

Abstract


hide
Yale University
Mon 31 Oct 2016, 3:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 31 Oct 2016, 3:00pm-4:00pm
hide
University of Oregon
Tue 1 Nov 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
ESB 2012
Tue 1 Nov 2016, 3:30pm-4:30pm

Abstract

 
hide
University of California, San Diego
Wed 2 Nov 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 2 Nov 2016, 3:00pm-4:00pm

Abstract

 TBA
hide
Princeton University
Fri 4 Nov 2016, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium--TBA
ESB 2012
Fri 4 Nov 2016, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments (A light reception) are served in ESB 4133 from 2:30pm-3:00pm before the colloquium.
hide
Stanford University
Tue 8 Nov 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
ESB 2012
Tue 8 Nov 2016, 3:30pm-4:30pm

Abstract

 
hide
University of Bath
Wed 9 Nov 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 9 Nov 2016, 3:00pm-4:00pm

Abstract

 TBA
hide
University of Washington
Wed 9 Nov 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
TBA
ESB 4133 (PIMS Lounge)
Wed 9 Nov 2016, 3:15pm-10:00am

Abstract


hide
TU Darmstadt, Department of Mechanical Engineering
Mon 14 Nov 2016, 3:00pm
Institute of Applied Mathematics
ESB 2012
New conservation laws of Euler and Navier-Stokes equations. Subtitle: Generic and dimensionally reduced cases for plane, axisymmetric and helically symmetric flows
ESB 2012
Mon 14 Nov 2016, 3:00pm-4:00pm

Abstract

It has long been known that 3D time-dependent Navier-Stokes equations for incompressible fluids admit the classical conservation laws (CL) of mass, momentum, angular momentum and centre-of-mass theorem. For inviscid flows, i.e. Eulers equation, this is extended by the conservation of helicity and energy. Employing the “direct method” (DM) by Anco, Bluman (1997) it has been shown that this set of conservation laws is complete for primitive variables. The DM is a substantial generalization of Noethers theorem and does not rely on a variational principle, and, further, is directly applicable to any type of differential equation, even dissipative ones.  With this an additional infinite set of CL for Navier-Stokes equations in vorticity formulation are derived. Various examples are shown.
Interesting enough, even more CLs exist for Euler and Navier-Stokes equations in spatially reduced coordinate systems such as for plane, axisymmetric and helically symmetric flows. E.g. an infinite set of CLs for the generalization of helicity has been derived, and, surprisingly, even new CL for plane flows haven been identified.

Note for Attendees

Tea served beforehand in ESB 4133 (PIMS lounge) 
hide
Massachusetts Institute of Technology
Wed 16 Nov 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 16 Nov 2016, 3:00pm-4:00pm

Abstract

 TBA
hide
Reed College
Wed 16 Nov 2016, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)
TBA
ESB 4133 (PIMS Lounge)
Wed 16 Nov 2016, 3:15pm-10:00am

Abstract


hide
Penn State
Fri 18 Nov 2016, 3:00pm
Department Colloquium
Math Annex 1100
TBA
Math Annex 1100
Fri 18 Nov 2016, 3:00pm-4:00pm

Abstract


hide
Purdue University
Mon 21 Nov 2016, 1:45pm
Harmonic Analysis Seminar
Mon 21 Nov 2016, 1:45pm-2:45pm

Abstract

 
hide
Johns Hopkins University
Mon 21 Nov 2016, 3:00pm SPECIAL
Department Colloquium
Math Annex 1100
Quests for Golden numbers, old and new
Math Annex 1100
Mon 21 Nov 2016, 3:00pm-4:00pm

Abstract


hide
Qingsan Zhu
UBC Math
Wed 23 Nov 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 23 Nov 2016, 3:00pm-4:00pm

Abstract

TBA
hide
Emory University
Fri 25 Nov 2016, 3:00pm SPECIAL
Department Colloquium
ESB 2012
TBA--PIMS-UBC Distinguished Colloquium
ESB 2012
Fri 25 Nov 2016, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments (A light reception) are served in ESB 4133 from 2:30pm-3:00pm before the colloquium.
hide
UBC Math
Wed 30 Nov 2016, 3:00pm
Probability Seminar
ESB 2012
TBA
ESB 2012
Wed 30 Nov 2016, 3:00pm-4:00pm

Abstract

 TBA
hide
University of California, San Diego
Fri 3 Mar 2017, 3:00pm SPECIAL
Department Colloquium
ESB2012
PIMS-UBC Distinguished Colloquium--TBA
ESB2012
Fri 3 Mar 2017, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments (A light reception) are served in ESB 4133 from 2:30pm-3:00pm before the colloquium.
hide
University of Grenoble
Fri 10 Mar 2017, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium-TBA
ESB 2012
Fri 10 Mar 2017, 3:00pm-4:00pm

Abstract

PIMS-UBC Distinguished Colloquium TBA

Note for Attendees

Refreshments (A light reception) are served in ESB 4133 from 2:30pm-3:00pm before the colloquium.
hide
University of Grenoble
Mon 13 Mar 2017, 3:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 13 Mar 2017, 3:00pm-4:00pm
hide
Umberto Zannier
SNS, Pisa
Fri 2 Mar 2018, 3:00pm SPECIAL
Department Colloquium
ESB2012
PIMS-UBC Distinguished Colloquium--TBA
ESB2012
Fri 2 Mar 2018, 3:00pm-4:00pm

Abstract

 
hide
 
Top