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, 3:30pm4:30pm
Abstract
Random walk on a group is an established but stillgrowing 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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Fri 12 Feb 2016, 1:00pm
Probability Seminar
MATH 126

Thermodynamic limit on the graph of Zigzag diagrams

MATH 126
Fri 12 Feb 2016, 1:00pm2:00pm
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 n1 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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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, 3:00pm4:00pm
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?
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Brown

Mon 22 Feb 2016, 3:00pm
Algebraic Geometry Seminar
MATH 126

TBA

MATH 126
Mon 22 Feb 2016, 3:00pm4:00pm
Abstract
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IMPACTHIV 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, 12:00pm1:00pm
Abstract
Public health program managers and policy makers are regularly faced with complex decisions that affect the health and wellbeing 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, datadriven 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 crosssector 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/industrialevent/160224pllkv .
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UBC

Thu 25 Feb 2016, 3:30pm
Number Theory Seminar
room MATH 126

The story of the LebesgueNagell equation and mathematical deadends

room MATH 126
Thu 25 Feb 2016, 3:30pm4:30pm
Abstract
The LebesgueNagell 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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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, 3:00pm4:00pm
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 squarefree (contains no induced fourcycle). 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, 3:00pm4:00pm
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, 3:00pm4:00pm
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 OldroydB 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.
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McGill University

Thu 3 Mar 2016, 3:30pm
Number Theory Seminar
room IRMACS 10901 (SFU)

TBA

room IRMACS 10901 (SFU)
Thu 3 Mar 2016, 3:30pm4:30pm
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, 3:00pm4:00pm
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, 3:30pm4:30pm
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, 3:00pm4:00pm
Abstract
The classical method of GelfandZetlin 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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Harvard University

Fri 18 Mar 2016, 3:00pm
SPECIAL
Department Colloquium / PIMS Seminars and PDF Colloquiums
ESB2012

PIMSUBC Distinguished ColloquiumThe Siegel Mass Formula, Tamagawa Numbers, and Nonabelian Poincare Duality

ESB2012
Fri 18 Mar 2016, 3:00pm4:00pm
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, 3:00pm4:00pm
Abstract
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Thu 24 Mar 2016, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 24 Mar 2016, 3:30pm4:30pm
Abstract
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Thu 31 Mar 2016, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 31 Mar 2016, 3:30pm4:30pm
Abstract
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Courant Institute, NYU

Fri 1 Apr 2016, 3:00pm
SPECIAL
Department Colloquium
ESB2012

PIMSUBC Distinguished ColloquiumTBA

ESB2012
Fri 1 Apr 2016, 3:00pm4:00pm
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, 3:30pm4:30pm
Abstract
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Thu 7 Apr 2016, 3:30pm
Number Theory Seminar
room MATH 126


room MATH 126
Thu 7 Apr 2016, 3:30pm4:30pm
Abstract
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Fri 9 Sep 2016, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumTBA

ESB 2012
Fri 9 Sep 2016, 3:00pm4:00pm
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, 3:30pm10:00am
Abstract
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University of Minnesota

Fri 23 Sep 2016, 3:00pm
SPECIAL
Department Colloquium
ESB 2012

PIMSUBC Distinguished ColloquiumTBA

ESB 2012
Fri 23 Sep 2016, 3:00pm4:00pm
Abstract
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Note for Attendees
Refreshments will be served in MATH 125 before the colloquium.