2017 Mar 06

Combinatorics: Zilin Jiang (Technion) "Relations between Tverberg points and central points"

11:00am to 1:00pm

Location:

Rothberg B220 (CS)
Speaker: Zilin Jiang (Technion) Title: Relations between Tverberg points and central points Abstract: Given 3n lines in general position in the plane, it is always possible to partition them into n triples of lines so that all the triangles, formed by the triples, share a common point. This result is known back in 1988 by J.P. Roudneff. Strangely, in higher dimensions, it is only proved by Roman Karasev for n that is a prime power.
2016 Mar 07

Combinatorics: Alexander Barvinok (U. Michigan), "Complex zeros and computational complexity of partition functions"

10:30am to 12:30pm

Location:

B220 Rothberg (CS and Engineering building)
Speaker: Alexander Barvinok, University of Michigan Title: Complex zeros and computational complexity of partition functions Abstract: I plan to discuss how complex zeros of combinatorial partition functions, such as permanents, their higher-dimensional versions, partition functions of graph homomorphisms, etc. are related to the complexity of computing the functions in the real domain. For example, the permanent of a complex matrix such that the real part of every entry is between
2016 Dec 29

Amitsur Algebra: Igor Rivin, "Random integer matrices"

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: Random integer matrices Abstract: I will discuss various models of random integer matrices, and their (occasionally surprising) properties. Some of the work discussed is joint with E. Fuchs.
2017 May 04

Amitsur Algebra: Jasbir Chahal, " A tale of three elliptic curves"

12:00pm to 1:00pm

Location:

Manchester 209
Title: A tale of three elliptic curves. Abstract: We will show how the arithmetic of three elliptic curves answers three old questions in the Euclidean geometry.
2016 Dec 08

Amitsur Algebra: George Glauberman (Chicago)

12:00pm to 1:15pm

Location:

Manchester Building, Room 209
Title: Fixed points of finite groups on modules Abstract: Suppose G is a finite group, p is a prime, S is a Sylow p-subgroup of G, and V is a G-module over a field of characteristic p. In some situations, an easy calculation shows that the fixed points of G on V are the same as the fixed points of the normalizer of S in G. Generalizations of this result have been obtained previously to study the structure of G for p odd. We plan to describe a new generalization for p = 2. (This is part of joint work with J. Lynd that removes the classification of finite simple groups
2017 Mar 02

Amitsur Algebra: Lev Glebsky, " Almost Congruence Extension Property for subgroups of free groups"

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: Almost Congruence Extension Property for subgroups of free groups. Abstract. The talk essentially based on: https://arxiv.org/abs/1606.02345 Let G be a group and H
2017 Feb 09

Amitsur Algebra: Evan DeCorte, "The spectral method for geometric colouring problems"

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: The spectral method for geometric colouring problems
2017 Jun 29

12:00pm to 1:00pm

Location:

Manchester 209
Title: Stability patterns in representation theory and applications Abstract: Many natural sequences of objects come equipped with group actions, e.g. the symmetric group on n letters acting on a space X_n. This leads to fundamental instability of invariants, such as homology, arising from the representation theory of the sequence of groups. Representation stability is a new and increasingly important set of ideas that describe a sense in which such sequence of representations (of different groups) stabilizes.
2017 Jan 12

Amitsur Algebra: Uriya First, "Semisimply degenerate quadratic forms and a conjecture of Grothendieck and Serre"

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: Semisimply degenerate quadratic forms and a conjecture of Grothendieck and Serre (joint work with E. Bayer-Fluckiger) Abstract:
2017 May 25

Amitsur Algebra: Katrin Tent, "Sharply 2- and 3-transitive groups"

12:00pm to 1:00pm

Location:

Manchester 209
The existence of sharply 2-transitive groups without regular normal subgroup was a longstanding open problem. Recently constructions have been given, at least in certain characteristics. We will survey the current state of the art and explain some constructions and their limitations. (joint work with E. Rips)
2016 Dec 22

Amitsur Algebra: Mark Sapir (Vanderbilt)

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: On groups with quadratic Dehn functions Abstract: This is a joint work with A. Olshanskii. We construct a finitely presented group with quadratic Dehn function and undecidable conjugacy problem.
2017 Mar 23

Amitsur Algebra: Daniel Palacin, "Pseudo-finite groups containing an involution with a finite centralizer"

12:00pm to 1:00pm

Location:

Manchester 209
Title: Pseudo-finite groups containing an involution with a finite centralizer.
2017 Jan 26

Amitsur Algebra: Lev Glebsky, "Approximations of groups and equations over groups"

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: Approximations of groups and equations over groups. Abstract: The talk is largely based on the paper which may be found here: https://authors.elsevier.com/a/1UN3b4~FOr6ze Abstract: Let G be a group and K a class of groups. I define a notion of approximation of G by K and give several characterizations of approximable by K groups. For example, the sofic groups, defined by B. Weiss, are the groups approximable by symmetric (or alternating) groups. In the case of sofic groups we have that the following are equivalent:
2017 Jan 19

Amitsur Algebra: Yiftach Barnea, "Old and New Results on Subgroup Growth in Pro-p Groups."

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
Title: Old and New Results on Subgroup Growth in Pro-p Groups. Abstract: I will survey our current knowledge about subgroup growth in pro-p growth. In particular I will present new solutions to long standing open problems in the area: 1. What is the minimal subgroup growth of non-$p$-adic analytic pro-$p$ groups? (Joint work with Benjamin Klopsch and Jan-Christoph Schlage-Puchta.) 2. What are the subgroup growths of the Grigorchuk group and the Gupta-Sidki groups? (Joint work with Jan-Christoph Schlage-Puchta.)
2017 Jun 22

Amitsur Algebra: Jan Dobrowolski

12:00pm to 1:00pm

Location:

Manchester 209
Title: Inp-minimal ordered groups. Abstract. The main goal of the talk is to present the proof of the theorem stating that inp-minimal (left)-ordered groups are abelian. This generalizes a previous result of P. Simon for bi-ordered inp-minimal groups.