2017 May 18

# Basic notions: Ehud de Shalit - The Loxton - van der Poorten conjecture

4:00pm to 5:00pm

Abstract: Adamczewski and Bell proved in the 2013 the Loxton - van der Poorten
conjecture. It says the following. Let f be a Laurent power series (with complex
coefficients) and let \sigma_p be the operator substituting x^p for x in f. Suppose that f satisfies a homogenous polynomial equation in the operator \sigma_p with
coefficients which are rational functions, and a similar equation in the operator \sigma_q where p and q are multiplicatively independent natural numbers. Then f is a rational function.
2015 Dec 23

# Eshnav: Dorit Aharonov - "The revolution of quantum information"

Dorit Aharonov
6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)
2017 Dec 13

# Eshnav: Ohad Noy Feldheim - "Lattices, Colorings and Magnets"

6:15pm to 7:15pm

## Location:

Math 2 (Manchester building)
2017 Apr 30

# Combinatorics: Amir Yehudayoff (Technion) TBA

Repeats every week every Sunday until Sun Jun 25 2017 except Sun Apr 30 2017.
11:00am to 1:00pm

11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm

## Location:

Rothberg B221 (CS building)
Speaker: Misha Tyomkyn (TAU)
Title: Lagrangians of hypergraphs and the Frankl-Furedi conjecture
Abstract:
Frankl and Furedi conjectured in 1989 that the maximum Lagrangian of
all r-uniform hypergraphs of given size m is realised by the initial
segment of the colexicographic order. For r=3 this was partially solved
by Talbot, but for r\geq 4 the conjecture was widely open. We verify
the conjecture for all r\geq 4, whenever
$\binom{t-1}{r} \leq m \leq \binom{t}{r}- \gamma_r t^{r-2}$
2015 Dec 24

# Amitsur Algebra: Michael Larsen (Indiana U)

12:00pm to 1:15pm

## Location:

Manchester Building (room 209), Jerusalem, Israel
Title: Character values on compact simple Lie groups
Abstract: This work is part of a joint project with Aner and others to find upper bounds for values of irreducible characters in two related settings: compact simple Lie groups and finite groups of Lie type. I will discuss the first case, presenting bounds of the form
$$|\chi(g)| = O(\chi(1)^\alpha),$$
2015 Nov 19

# Amitsur Algebra: Avinoam Mann (HUJI), "Irreducible characters of some p-groups"

12:00pm to 1:15pm

## Location:

Manchester Building (room 209), Jerusalem, Israel
Abstract: We will discuss the characters of some classes of finite p-groups, in particular groups of maximal class and generalizations, and normally monomial groups.
2016 Jan 14

# Amitsur Algebra: Frauke Bleher (U of Iowa): Holomorphic differentials in positive characteristic

12:00pm to 1:15pm

## Location:

Manchester Building (room 209), Jerusalem, Israel
Title: Holomorphic differentials in positive characteristic
Abstract: This talk is about joint work with Ted Chinburg and Aristides Kontogeorgis.
Let X be a smooth projective curve over an algebraically closed field
k of positive characteristic p. Suppose G is a finite group with non-trivial
2015 Dec 03

# Amitsur Algebra: Boris Plotkin (Hebrew U)

12:00pm to 1:15pm

## Location:

Manchester Building (room 209), Jerusalem, Israel
Title: Algebraic Geometry in an arbitrary variety of algebras and Algebraic Logic
Abstract: I will speak about a system of notions which lead to interesting new problems for groups and algebras as well as to reinterpretation of some old ones.
2016 Mar 08

# Dynamics & probability: Elon Lindenstrauss (Mean dimension and embedding of Z^d actions)

2:00pm to 3:00pm

## Location:

Manchester building, Hebrew University of Jerusalem, (Room 209)
2016 Mar 29

# Dynamics & probability: Paul Nelson (ETH) - Microlocal lifts and quantum unique ergodicity on GL(2,Q_p)

2:00pm to 3:00pm

## Location:

Manchester building, Hebrew University of Jerusalem, (Room 209)
Abstract:
There are by now several celebrated measure classification results to the effect that a measure is uniform provided it possesses sufficient "invariance" as quantified by stabilizer, entropy, or recurrence. In some applications, part of the challenge is to identify or construct measures to which these hypotheses apply.
2018 Jan 15

# Michael Farber: "Robot motion planning and equivariant Bredon cohomology"

9:00am to 11:00am

## Location:

IIAS, Feldman Building, Givat Ram

Abstract: The motion planning problem of robotics leads to an interesting invariant of topological spaces, TC(X), depending on the homotopy type of X = the configuration space of the system. TC(X) is an integer reflecting the complexity of motion planning algorithms for all systems (robots) having X as their configuration space. Methods of algebraic topology allow to compute or to estimate TC(X) in many examples of practical interest. In the case when the space X is aspherical the number TC(X) depends only on the fundamental group of X.

2018 Jan 22

# HD-Combinatorics: Frank Calegari, "Methods for computing homology and cohomology"

9:00am to 11:00am

## Location:

IIAS, Feldman Building, Givat Ram
Abstract: We describe some different techniques for studying cohomology (both rationally and integrally), including the idea of studying "towers" (of spaces or groups).
Examples include the circle, the Alexander polynomial of a knot, and arithmetic groups.
2018 Mar 12

# HD-Combinatorics Special Day: Cohomology of sheaves on graphs and complexes (organized by Uriya First)

(All day)

## Location:

IIAS, Feldman Building, Givat Ram
2018 Mar 05

# HD-Combinatorics Special Day: Samplers in Computer Science (organized by Amnon Ta-Shma)

(All day)

## Location:

Room 130, IIAS, Feldman Building, Givat Ram

All talks will be given by Amnon Ta-Shma.
10:00-11:00 - The sampling problem and some equivalent formulations

11:30-12:30 - A basic "combinatorial" construction

14:00-14:45 - Algebraic constructions of randomness condensers

15:15-16:00 - Structured sampling

Program:

1. 10:00-11:00 - The sampling problem and some equivalent formulations.
Abstract:
We will first define Samplers, and the parameters that
one usually tries to optimize: accuracy, confidence, query complexity
2018 Mar 22

# Colloquium: Gilles Zemor (Université de Bordeaux) - "Additive Combinatorics in Field Extensions"

3:30pm to 4:30pm

## Location:

Manchester Building (Hall 2), Hebrew University Jerusalem
Additive combinatorics enable one to characterize subsets S of elements in a group such that S+S has small cardinality. We are interested in linear analogues of these results, namely characterizing subspaces S in some algebras (mostly extension fields) such that the linear span of the set S^2 of products st, for s,t in S, has small dimension. We shall present a linear analogue of a theorem of Vosper which says that under the right conditions, a sufficiently small dimension for S^2 implies that S has a basis of elements in geometric progression.