Group Theory

Iwahori-Hecke algebras are Gorenstein (part II)

Submitted by root on Wed, 2012-10-24 13:21
Speaker: 
Peter Schneider
Date: 
Tue, Oct 23, 2012
Location: 
PIMS, University of British Columbia
Conference: 
PIMS Speaker series
Abstract: 
n the local Langlands program the (smooth) representation theoryof p-adic reductive groups G in characteristic zero plays a key role. For any compact open subgroup K of G there is a so called Hecke algebra H(G,K). The representation theory of G is equivalent to the module theories over all these algebras H(G,K). Very important examples of such subgroups K are the Iwahori subgroup and the pro-p Iwahori subgroup. By a theorem of Bernstein the Heckealgebras of these subgroups (and many others) have finite global dimension. In recent years the same representation theory of G but over an algebraically closed field of characteristic p has become more and more important. But little is known yet. Again one can define analogous Hecke algebras. Their relation to the representation theory of G is still very mysterious. Moreover they are no longer of finite global dimension. In joint work with R. Ollivier we prove that over any field the algebra H(G,K), for K the (pro-p) Iwahori subgroup, is Gorenstein.

Iwahori-Hecke algebras are Gorenstein (part I)

Submitted by root on Wed, 2012-10-24 12:30
Speaker: 
Peter Schneider
Date: 
Wed, Oct 17, 2012
Location: 
PIMS, University of British Columbia
Conference: 
PIMS Speaker series
Abstract: 
N.B. Due to problems with our camera, there is some audio distortion on this file and a small portion of the video has been removed.

This lecture is the first of a two part series (part II).

In the local Langlands program the (smooth) representation theory of p-adic reductive groups G in characteristic zero plays a key role. For any compact open subgroup K of G there is a so called Hecke algebra H(G,K). The representation theory of G is equivalent to the module theories over all these algebras H(G,K). Very important examples of such subgroups K are the Iwahori subgroup and the pro-p Iwahori subgroup. By a theorem of Bernstein the Hecke algebras of these subgroups (and many others) have finite global dimension.

In recent years the same representation theory of G but over an algebraically closed field of characteristic p has become more and more important. But little is known yet. Again one can define analogous Hecke algebras. Their relation to the representation theory of G is still very mysterious. Moreover they are no longer of finite global dimension. In joint work with R. Ollivier we prove that over any field the algebra H(G,K), for K the (pro-p) Iwahori subgroup, is Gorenstein.

Quadratic forms and finite groups

Submitted by root on Wed, 2012-10-17 16:51
Speaker: 
Eva Bayer
Date: 
Fri, Sep 28, 2012
Location: 
PIMS, University of British Columbia
Conference: 
PIMS/UBC Distinguished Colloquium
Abstract: 
The study of quadratic forms is a classical and important topic of algebra and number theory. A natural example is the trace form of a finite Galois extension. This form has the additional property of being invariant under the Galois group,leading to the notion of "self-dual nornal basis", introduced by Lenstra. The aim of this talk is to give a survey of this area, and to present some recent joint results with Parimala and Serre.

Asymptotic dimension

Submitted by root on Fri, 2012-06-01 10:42
Speaker: 
Mladen Bestvina
Date: 
Mon, May 28, 2012
Location: 
PIMS, University of British Columbia
Conference: 
PIMS Distinguished Lecturer
Abstract: 
Most of the talk will be an introduction to (second) bounded cohomology of a discrete group. I will explain classical constructions of bounded cocycles and recent results (joint with Bromberg and Fujiwara) regarding mapping class groups and a construction of bounded cocycles with coefficients in an arbitrary unitary representation.

Second Bounded Cohomology

Submitted by root on Thu, 2012-05-31 17:52
Speaker: 
Mladen Bestvina
Date: 
Mon, May 28, 2012
Location: 
PIMS, University of British Columbia
Conference: 
PIMS Distinguished Lecturer
Abstract: 
Most of the talk will be an introduction to (second) bounded cohomology of a discrete group. I will explain classical constructions of bounded cocycles and recent results (joint with Bromberg and Fujiwara) regarding mapping class groups and a construction of bounded cocycles with coefficients in an arbitrary unitary representation.

Regular Permutation Groups and Cayley Graphs

Submitted by root on Mon, 2011-10-17 13:43
Speaker: 
Cheryl E. Praeger
Date: 
Fri, Jul 10, 2009
Location: 
University of New South Wales, Sydney, Australia
Conference: 
1st PRIMA Congress
Abstract: 
Regular permutation groups are the `smallest' transitive groups of permutations, and have been studied for more than a century. They occur, in particular, as subgroups of automorphisms of Cayley graphs, and their applications range from obvious graph theoretic ones through to studying word growth in groups and modeling random selection for group computation. Recent work, using the finite simple group classification, has focused on the problem of classifying the finite primitive permutation groups that contain regular permutation groups as subgroups, and classifying various classes of vertex-primitive Cayley graphs. Both old and very recent work on regular permutation groups will be discussed.

Expanders, Group Theory, Arithmetic Geometry, Cryptography and Much More

Submitted by root on Mon, 2011-10-17 13:43
Speaker: 
Eyal Goran
Date: 
Tue, Apr 6, 2010
Location: 
University of Calgary, Calgary, Canada
CRG: 
Number Theory (2010-2013)
Abstract: 
This is a lecture given on the occasion of the launch of the PIMS CRG in "L-functions and Number Theory". The theory of expander graphs is undergoing intensive development. It finds more and more applications to diverse areas of mathematics. In this talk, aimed at a general audience, I will introduce the concept of expander graphs and discuss some interesting connections to arithmetic geometry, group theory and cryptography, including some very recent breakthroughs.

Algebraic Z^d-actions

Submitted by Gotay on Mon, 2011-04-18 13:58
Author: 
Klaus Schmidt
Date: 
Fri, Nov 1, 2002
Location: 
University of Victoria, Victoria, Canada
Conference: 
PIMS Distinguished Chair Lectures
Abstract: 

This is a written account of five Pacific Institute for the Mathematical Sciences Distinguished Chair Lectures given at the Mathematics Department, University of Victoria, BC, in November 2002. The lectures were devoted to the ergodic theory of $ \mathbb Z^d $--actions, i.e. of several commuting automorphisms of a probability space. After some introductory remarks on more general $ \mathbb Z^d $-actions the lectures focused on ‘algebraic’ $ \mathbb Z^d $-actions, their sometimes surprising properties, and their deep connections with algebra and arithmetic. Special emphasis was given to some of the very recent developments in this area, such as higher order mixing behaviour and rigidity phenomena.

Notes: 
application/pdf iconSchmidt.pdf

Exponential Sums Over Multiplicative Groups in Fields of Prime Order and Related Combinatorial Problems

Submitted by Gotay on Thu, 2011-04-14 12:09
Author: 
Sergei Konyagin
Date: 
Thu, Apr 1, 2004
Location: 
University of British Columbia, Vancouver, Canada
Conference: 
PIMS Distinguished Chair Lectures
Abstract: 

Let $ p $ be a prime. The main subject of my talks is the estimation of exponential sums over an arbitrary subgroup $ G $ of the multiplicative group $ {\mathbb Z}^*_p $:

$$S(a, G) = \sum_{x\in G} \exp(2\pi iax/p), a \in \mathbb Z_p.$$

These sums have numerous applications in additive problems modulo $ p $, pseudo-random generators, coding theory, theory of algebraic curves and other problems.

Notes: 
application/pdf iconKonyagin_Lectures.pdf
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