Events & Seminars

2016 Dec 26

Combinatorics: Adam Sheffer (CalTech) "Geometric Incidences and the Polynomial Method"

10:00am to 11:45am

Location: 

B220 Rothberg (CS)
Speaker: Adam Sheffer, CalTech Title: Geometric Incidences and the Polynomial Method Abstract: While the topic of geometric incidences has existed for several decades, in recent years it has been experiencing a renaissance due to the introduction of new polynomial methods. This progress involves a variety of new results and techniques, and also interactions with fields such as algebraic geometry and harmonic analysis.
2017 Oct 23

Combinatorics seminar: Quang Nhat Le

11:00am to 12:30pm

Location: 

Eilat Hall at the IIAS
Title: Counting lattice points inside a d-dimensional polytope via Fourier analysis Abstract: Given a convex body $B$ which is embedded in a Euclidean space $R^d$, we can ask how many lattice points are contained inside $B$, i.e. the number of points in the intersection of $B$ and the integer lattice $Z^d$. Alternatively, we can count the lattice points inside B with weights, which sometimes creates more nicely behaved lattice-point enumerating functions.
2016 Oct 31

Combinatorics: Gil kalai (HU) "Algebraic-topological invariants of hypergraphs and extremal combinatorics"

11:00am to 1:00pm

Location: 

Rothberg (CS) B220
Speaker: Gil Kalai, HU Title: Algebraic-topological invariants of hypergraphs and extremal combinatorics Abstract: We will discuss some algebraic invariants of hypergraphs and some connection to algebraic topology. We will present some conjectural (rather speculative) relations with two central problems in extremal combinatorics: The Turan (4,3) conjecture and the Erdos-Rado sunflower conjecture.
2017 Mar 27

Combinatorics: Micha Sharir (TAU) "Eliminating depth cycles for lines and triangles, with applications to bounding incidences"

11:00am to 1:00pm

Location: 

Rothberg B220 (CS bldg)
Speaker: Micha Sharir (Tel Aviv University) Title: Eliminating depth cycles for lines and triangles, with applications to bounding incidences Abstract: --------- The talk presents three related results. We first consider the problem of eliminating all depth cycles in a set of n lines in 3-space. For two lines l_1, l_2 in 3-space (in general position), we say that l_1 lies below l_2 if the unique vertical line that meets both lines meets l_1 at a point below the point where it meets l_2. This depth relationship typically has cycles, which can be eliminated if we cut the lines into
2016 Dec 19

Combinatorics: Lukas Kühne (U. Bonn) "Heavy hyperplanes in multiarrangements and their freeness"

11:00am to 1:00pm

Location: 

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 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.
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.
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 Jun 29

Amitsur Algebra: Nir Gadish

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.

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