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 Events
Bob Hough
Institute for Advanced Study, Princeton
Thu 11 Feb 2016, 3:30pm
Discrete Math Seminar
MATH 126
Random walk on unipotent groups
MATH 126
Thu 11 Feb 2016, 3:30pm-4:30pm

Abstract

Random walk on a group is an established but still-growing field.  I discuss aspects of recent work, alone and joint with Persi Diaconis, on random walks on unipotent groups.  Among our results, we have a new local limit theorem for random walk on the Heisenberg group, which applies to arbitrary centered measures of compact support and obtains an optimal rate. There is also a mixing time bound of degree times diameter squared for the mixing time of random walk on some Cayley graphs of cyclic groups.
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Pierre Tarrago
Fri 12 Feb 2016, 1:00pm
Probability Seminar
MATH 126
Thermodynamic limit on the graph of Zigzag diagrams
MATH 126
Fri 12 Feb 2016, 1:00pm-2:00pm

Abstract

 In this talk, I will first introduce the notions of Gibbs measures and thermodynamic limit on graded graphs, as they were defined by the Russian school (Vershik, Kerov, Olshanski,...). Then, I will present some results related to the thermodynamic limit on the graph of Zigzag diagrams: the latter is a graded graph whose set of vertices of degree n consists of words of length n-1 in two letters, and such that the edge structure is given by a simple combinatorial relation between words of consecutive lengths. This graph is related to the Young graph, and I will explain this relation by mapping paths on the graph of Zigzag diagrams to paths on the Young graph. "
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Bob Hough
Institute for Advanced Study, Princeton
Fri 12 Feb 2016, 3:00pm
Department Colloquium
MATX 1100
Covering systems of congruences and the Lovasz Local Lemma
MATX 1100
Fri 12 Feb 2016, 3:00pm-4:00pm

Abstract

The Lov\'{a}sz Local Lemma is a powerful technique from probabilistic combinatorics for treating many rare events with localized dependence structure.  I discuss the local lemma and its application in my negative solution to the following problem of Erd\H{o}s.

A distinct covering system of congruences is a collection of arithmetic progressions
 
a_i \bmod m_i, \qquad 1 < m_1 < m_2 < ... < m_k

whose union is the integers. Can m_1 be arbitrarily large?

Note for Attendees

Refreshments will be served in MATH 125 before the colloquium.
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Brown
Mon 22 Feb 2016, 3:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 22 Feb 2016, 3:00pm-4:00pm

Abstract


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Krisztina Vasarhelyi
IMPACT-HIV and SFU Health Sciences
Wed 24 Feb 2016, 12:00pm
PIMS Seminars and PDF Colloquiums
UBC Robson Square
PIMS Vancouver Lunchbox Lecture: Systems Modeling for HIV Health Service Delivery
UBC Robson Square
Wed 24 Feb 2016, 12:00pm-1:00pm

Abstract

Public health program managers and policy makers are regularly faced with complex decisions that affect the health and well-being of the public. Mathematical models and operations research tools can be used to consider diverse interacting factors, such as the epidemiology and clinical aspects of a condition, delivery methods of health services, and constraints on budget and resources. Creating reliable, data-driven models that are tractable and useful for informing policy decisions requires close collaboration of stakeholders and mathematicians.

This presentation will describe a health systems modeling project to inform the delivery of HIV health services in Vancouver, which illustrates the promise, challenges and rewards of cross-sector collaborations and offers possible avenues for the expanded use of modeling in public policy.

Registration is free and a light lunch will be provided. For more details and to register for this event, please visit http://www.pims.math.ca/industrial-event/160224-pllkv .


Note for Attendees

About the PIMS Lunchbox Series

The PIMS Lunch Box Series create a beneficial link between researchers in industry and academics in the mathematical sciences. Researchers with industrial and commercial concerns are invited to present their current work, demonstrating how the latest advances in the mathematical sciences apply to current, real-world issues in industrial processes such as seismic and medical imaging, financial mathematics and complex fluids. PIMS has been holding lunchbox lectures in Calgary for seven years and is now expanding to Vancouver. To learn more about PIMS, please visit  www.pims.math.ca<http://www.pims.math.ca> .


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UBC
Thu 25 Feb 2016, 3:30pm
Number Theory Seminar
room MATH 126
The story of the Lebesgue-Nagell equation and mathematical dead-ends
room MATH 126
Thu 25 Feb 2016, 3:30pm-4:30pm

Abstract

The Lebesgue-Nagell equation is a Diophantine equation that arises in a variety of contexts, ranging from the classification of finite simple groups to Catalan’s problem. In this talk, we will discuss a variety of approaches to this equation that share the common thread of failing to solve it. This is joint work with Aaron Levin.
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Maria Chudnovsky
Princeton University
Fri 26 Feb 2016, 3:00pm SPECIAL
Department Colloquium / PIMS Seminars and PDF Colloquiums
ESB 2012
Coloring some perfect graphs -PIMS/UBC Distinguished Colloquium
ESB 2012
Fri 26 Feb 2016, 3:00pm-4:00pm

Abstract

Perfect graphs are a class of graphs that behave particularly well with respect to coloring. In the 1960's Claude Berge made two conjectures about this class of graphs, that motivated a great deal of
research, and by now they have both been solved.

The following remained open however: design a combinatorial algorithm that produces an optimal coloring of a perfect graph. Recently, we were able to make progress on this question, and we will discuss it in this talk. Last year, in joint work with Lo, Maffray, Trotignon and Vuskovic we were able to construct such an algorithm under the additional assumption that the input graph is square-free (contains no induced four-cycle). More recently, together with Lagoutte, Seymour and Spirkl, we solved another case of the problem, when the clique number of the input graph is fixed (and not part of the input).

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MIT
Mon 29 Feb 2016, 3:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 29 Feb 2016, 3:00pm-4:00pm

Abstract


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DAMTP, Cambridge University
Mon 29 Feb 2016, 3:00pm SPECIAL
Institute of Applied Mathematics
LSK 460
Explaining the flow of elastic liquids
LSK 460
Mon 29 Feb 2016, 3:00pm-4:00pm

Abstract

The behaviour of elastic liquids does not follow simply from our understanding of both elastic solids and viscous liquids. Four anomalous behaviours will be discussed :-- (i) long wakes at low Reynolds numbers, (ii) large vortices upstream of a constriction, (iii) long times for capillary forces to squeeze a filament, and (iv) different devices measuring wildly different values of `the' extensional viscosity for the international standard liquid M1. Many features can be explained and understood using the simplest constitutive equation, that of an Oldroyd-B fluid, which generates the important ideas of tension in streamlines and delays for the stress to respond. This model fluid has however an undesirable negative viscosity under certain conditions, which can be regularized  by requiring a finite extensibility of the underlying microstructure, in the FENE modification. This modification enables the remain anomalous behaviours to be understood, with a high extensional viscosity to increase drag and an anisotropy to create the long upstream vortices.

Note for Attendees

This is an IAM/PIMS distinguished speaker. Tea will be served before the talk in the IAM lounge (LSK 306). 
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Jan Vonk
McGill University
Thu 3 Mar 2016, 3:30pm
Number Theory Seminar
room IRMACS 10901 (SFU)
TBA
room IRMACS 10901 (SFU)
Thu 3 Mar 2016, 3:30pm-4:30pm

Abstract

 
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UC Berkeley
Fri 4 Mar 2016, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS Hugh Morris Lecture
ESB 2012
Fri 4 Mar 2016, 3:00pm-4:00pm

Abstract


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UBC/PIMS
Thu 10 Mar 2016, 3:30pm
Number Theory Seminar
room MATH 126
Some finiteness results on monogenic orders in arbitrary characteristic
room MATH 126
Thu 10 Mar 2016, 3:30pm-4:30pm

Abstract


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University of Toronto
Fri 11 Mar 2016, 3:00pm
Department Colloquium
Math Annex 1100
Monodromy of shift of argument eigenvectors and cactus groups
Math Annex 1100
Fri 11 Mar 2016, 3:00pm-4:00pm

Abstract

The classical method of Gelfand-Zetlin constructs bases in representations of gl_n using iterative restriction to smaller gl_k. For any semisimple Lie algebra this can be generalized using eigenvectors for maximal commutative subalgebra of universal envelopping algebras. In this way, we obtain a family of bases for representations of our Lie algebra. This family is parametrized by the moduli space of marked genus 0 real curves. The fundamental group of this moduli space is called the cactus group and thus we obtain an an action of the cactus group on one of these bases. This action of the cactus group matches an action defined combinatoriallyusing crystals.
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Jacob Lurie
Harvard University
Fri 18 Mar 2016, 3:00pm SPECIAL
Department Colloquium / PIMS Seminars and PDF Colloquiums
ESB2012
PIMS-UBC Distinguished Colloquium--The Siegel Mass Formula, Tamagawa Numbers, and Nonabelian Poincare Duality
ESB2012
Fri 18 Mar 2016, 3:00pm-4:00pm

Abstract

Let L be a positive definite lattice. There are only finitely many positive definite lattices L' which are isomorphic to L modulo N for every N > 0: in fact, there is a formula for the number of such lattices, called the Siegel mass formula. In this talk, I'll review the Siegel mass formula and explain how it was reformulated by Weil as a statement about volumes of adelic groups. I'll then describe some joint work with Dennis Gaitsgory on computing these volumes over function fields using ideas from topology: in particular, a nonabelian version of Poincare duality.
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Western Ontario
Mon 21 Mar 2016, 3:00pm
Algebraic Geometry Seminar
MATH 126
TBA
MATH 126
Mon 21 Mar 2016, 3:00pm-4:00pm

Abstract


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TBA
Thu 24 Mar 2016, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 24 Mar 2016, 3:30pm-4:30pm

Abstract

 
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TBA
Thu 31 Mar 2016, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 31 Mar 2016, 3:30pm-4:30pm

Abstract

 
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Robert Kohn
Courant Institute, NYU
Fri 1 Apr 2016, 3:00pm SPECIAL
Department Colloquium
ESB2012
PIMS-UBC Distinguished Colloquium--TBA
ESB2012
Fri 1 Apr 2016, 3:00pm-4:00pm

Abstract

 
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Oklahoma State University
Thu 7 Apr 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Thu 7 Apr 2016, 3:30pm-4:30pm

Abstract


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TBA
Thu 7 Apr 2016, 3:30pm
Number Theory Seminar
room MATH 126
room MATH 126
Thu 7 Apr 2016, 3:30pm-4:30pm

Abstract

 
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G. Huisken
Fri 9 Sep 2016, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium--TBA
ESB 2012
Fri 9 Sep 2016, 3:00pm-4:00pm

Abstract

 
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University of Minnesota
Tue 20 Sep 2016, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
ESB 2012
TBA
ESB 2012
Tue 20 Sep 2016, 3:30pm-10:00am

Abstract


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University of Minnesota
Fri 23 Sep 2016, 3:00pm SPECIAL
Department Colloquium
ESB 2012
PIMS-UBC Distinguished Colloquium--TBA
ESB 2012
Fri 23 Sep 2016, 3:00pm-4:00pm

Abstract


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