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 Events
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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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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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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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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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
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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