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.
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 $$|\chi(g)| = O(\chi(1)^\alpha),$$
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.
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)
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
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.
2017 Nov 21

# T&G: Semyon Alesker (Tel Aviv University), Calabi type problem for Monge-Ampere equations on HKT manifolds

12:00pm to 1:30pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
Real and complex Monge-Ampere equations play a central role in several branches of geometry and analysis. We introduce a quaternionic version of a Monge-Ampere equation which is an analogue of the famous Calabi problem in the complex case. It is a non-linear elliptic equation of second order on so called HyperKahler with Torsion (HKT) manifolds (the latter manifolds were introduced by physicists in 1990's). While in full generality it is still unsolved, we will describe its solution in a special case and some
2016 Mar 20

# Game Theory & Math Economics: Gilad Bavly and Ron Peretz (Bar-Ilan) - "Limits of Correlation with Bounded Complexity"

4:00pm to 5:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
Peretz (2013) showed that, perhaps surprisingly, players whose recall is bounded can correlate in a long repeated game against a player of greater recall capacity. We show that correlation is already impossible against an opponent whose recall capacity is only linearly larger. This result closes a gap in the characterisation of min-max levels, and hence also equilibrium payoffs, of repeated games with bounded recall.
2015 Nov 01

# Game Theory & Math Economics: Abraham Neyman (HUJI) - "Additive valuations of streams of payoffs that obey the time-value of money principle: Characterization and robust optimization"

4:00pm to 5:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
This paper characterizes the ordinal utilities over the bounded infinite streams of payoffs that satisfy the time-value of money principle and an additivity property, and those that in addition are impatient. Building on this characterization, the paper introduces the concept of optimization that is robust to small imprecision in the specification of the preference, and proves that the set of feasible streams of payoffs of a finite Markov Decision Process admits such a robust optimization.
2016 May 15

# Game Theory & Math Economics: Talia Einhorn (Tel Aviv University & Ariel University) - "Israel's Legal Infrastructure – walking on thin ice"

4:00pm to 5:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
A sound legal infrastructure is critical to the development of the Israeli economy. In its absence, business people and private persons alike face difficulties in planning their actions. All too often they are obliged to turn to the courts of law. However, in the absence of a proper infrastructure, those do not themselves have the necessary tools to resolve the disputes. The matters at issue are not marginal. They have long-lasting consequences for the economy. The number of publicly-traded companies listed in Tel-Aviv Stock Exchange sank from 657 in 2008 to 461 in March 2016.
2015 Nov 22

# Game Theory & Math Economics: Sergiu Hart (HUJI) - "Calibrated Forecasts, Leaks, and Game Equilibria" (joint work with Dean P. Foster)

4:00pm to 5:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
How good is a forecaster? Assume for concreteness that every day the forecaster issues a forecast of the type "the chance of rain tomorrow is 30%." A simple test one may conduct is to calculate the proportion of rainy days out of those days that the forecast was 30%, and compare it to 30%; and do the same for all other forecasts. A forecaster is said to be _calibrated_ if, in the long run, the differences between the actual proportions of rainy days and the forecasts are small—no matter what the weather really was.
2016 Jun 19

# Game Theory & Math Economics: Jacob (Kobi) Glazer (Tel Aviv University) - "Has the National Health Insurance Law Run its Course?"

4:00pm to 5:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus

The National Health Insurance Law is operated through several economic mechanisms that are meant to implement its vision. In this lecture we will present the main flaws of some of these mechanisms and propose ways to fix them. The lecture will be in hebrew.