2017
Dec
11

# Combinatorics seminar: Leonard Schulman

11:00am to 12:30pm

## Location:

Eilat Hall at IIAS

Title: The Invisible Hand of Laplace Read more about Combinatorics seminar: Leonard Schulman

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2017
Dec
11

11:00am to 12:30pm

Eilat Hall at IIAS

Title: The Invisible Hand of Laplace Read more about Combinatorics seminar: Leonard Schulman

2016
Dec
19

11:00am to 1:00pm

Rothberg B220 (CS)

Speaker: Lukas Kühne (University of Bonn)
Title: Heavy hyperplanes in multiarrangements and their freeness
Abstract:
One of the central topics among the theory of hyperplane arrangements is their freeness. Terao's conjecture tries to link the freeness with the combinatorics of an arrangement. One of the few categories of arrangements which satisfy this conjecture consists of 3-dimensional arrangements with an unbalanced Ziegler restriction. This means that the arrangement contains a lot of hyperplanes intersecting in one single line

2017
Nov
20

11:00am to 12:30pm

IIAS Room 130

Speaker 1: Sria Louis
Title: Asymptotically Almost Every 2r-regular Graph has an Internal Partition
Abstract: An internal partition of a graph is a partitioning of the vertex set into two parts such that for every vertex, at least half of its neighbors are on its side. It is easy to notice that such a partition doesn't always exist (e.g. - cliques), though, both the existence and finding of such a partition - are open problems.
Stiebitz (1996), responding to a problem of Thomassen (1983), made a breakthrough in this area, but the question and some interesting generalizations are still open.

2017
Mar
06

11:00am to 1:00pm

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

10:30am to 12:30pm

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

12:00pm to 1:00pm

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

12:00pm to 1:00pm

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

12:00pm to 1:15pm

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

12:00pm to 1:00pm

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

12:00pm to 1:00pm

Manchester Building, Room 209

Title: The spectral method for geometric colouring problems

2017
Jun
29

12:00pm to 1:00pm

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

12:00pm to 1:00pm

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

12:00pm to 1:00pm

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

12:00pm to 1:00pm

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

12:00pm to 1:00pm

Manchester 209

Title: Pseudo-finite groups containing an involution with a finite centralizer.