• 2021 Jan 20

# Analysis Seminar: Dirk Hundertmark (Karlsruhe) "Quantum Systems at the Brink: Helium"

12:00pm to 1:00pm

## Location:

Zoom

Title: Quantum Systems at the Brink: Helium

Abstract: Perturbation theoryworks well for the the discrete spectrum below the essential spectrum. Whathappens if a parameter of a quantum system is tuned in such a way that abound state energy (e.g. the ground state energy) hits the bottom of theessential spectrum? Does the eigenvalue survive, i.e., the correspondingeigenfunction stays $L^2$, or does it dissolve into the continuumenergies?

It turns out the

• 2021 Jan 20

# Logic Seminar - Eran Alouf

11:30am to 1:15pm

## Location:

https://huji.zoom.us/j/82821066522?pwd=aVJnTkxBYktycHdzNFN5WDV0R2FkZz09
Dp-minimal expansions of (Z,+)

Abstract:
I will review the research about dp-minimal expansions of (Z,+), and then present a recent result classifying (Z,+,<) as the unique dp-minimal expansion of (Z,+) defining an infinite subset of N.
All the relevant notions will be defined in the talk.
• 2021 Jan 19

# Dynamics seminar: Barak Weiss (TAU). Ergodicity of rel foliations on the space of holomorphic one forms

2:00pm to 3:00pm

Abstract: The rel foliation is a foliation of the moduli space of abelian differentials obtained by "moving the zeroes of the one form while keeping all absolute periods fixed". It has been studied in complex analysis and dynamics under different names (isoperiodic foliation, Schiffer variation, kernel foliation). Until recent years the question of its ergodicity was wide open. Recently partial results were obtained by Calsamiglia-Deroin-Francaviglia and by Hamenstadt. In our work we completely resolve the ergodicity question.
• 2021 Jan 19

# Tom Meyerovich (BGU) "Markovian properties of continuous group actions: algebraic actions, entropy and the homoclinic group"

12:00pm to 1:00pm

following Sebastián Barbieri, Felipe García-Ramos and Hanfeng Li
https://arxiv.org/abs/1911.00785

Zoom details:
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Meeting ID: 837 2635 1672
Passcode: 7e288r
• 2021 Jan 18

# Combinatorics: Shinichi Tanigawa

11:00am to 1:00pm

## Location:

https://huji.zoom.us/j/81176578450?pwd=TStYWHhhWnE3YkNuR0RlZmkrejBIUT09

HUJI Combinatorics Seminar

When: Monday Jan 18th, 2021, at 11AM (Israel time)

Zoom link: https://huji.zoom.us/j/81176578450?pwd=TStYWHhhWnE3YkNuR0RlZmkrejBIUT09

Speaker: Shin-ichi Tanigawa (University of Tokyo)

Title: Maximal Matroid Problem on Graphs

Abstract:
• 2021 Jan 17

# Kazhdan seminar: Tomer Schank "Sheaves with nilpotent support"

Repeats every week every Sunday until Sun Jan 17 2021 .
2:00pm to 4:00pm

Abstract: Given a smooth and proper curve X and a reductive group G one can consider the stack Bun_{G,X} of principal G-bundles on X. This stack has an important role in Algebraic Geometry and Representation Theory especially with regard to the Langlands program. We shall study the geometry of Bun_{G,X} and the category
D(G,X) of constructible  sheaves on Bun_{G,X}. We shall be especially interested in the subcategory D_{nil}(G,X) of sheaves with nilpotent singular support.
• 2021 Jan 17

# Kazhdan seminar : Ari Shnidman "Fundamental lemmas and Fourier transform"

Repeats every week every Sunday until Sun Jan 17 2021 .
11:00am to 1:00pm

Abstract: A fundamental lemma is an identity relating p-adic integrals on two different groups. These pretty identities fit into a larger story of trace formulas and special values of L-functions.  Our goal is to present recent work of Beuzart-Plessis on the Jacquet-Rallis fundamental lemma, comparing integrals on GL(n) and U(n).
• 2021 Jan 14

# Basic Notions: Kobi Peterzil (U. of Haifa) "The Pila-Zannier method: applications of model theory to Diophantine geometry".

4:00pm to 5:15pm

## Location:

Zoom

A family of problems in Diophantine geometry has the following
form: We fix a collection of "special" algebraic varieties among which the
0-dimensional are called "special points". Mostly, if V is a special variety
then the special points are Zariski dense in V, and the problem is to prove
the converse: If V is an irreducible algebraic variety and the special
points are Zariski dense in V then V itself is special.

Particular cases of the above are the Manin-Mumford conjecture

• 2021 Jan 13

# Set Theory seminar - Juris Stperans (York) Universal functions, strong colourings and ideas from PID

2:00pm to 4:00pm

Juris Stperans will speak about

Universal functions, strong colourings and ideas from PID

A construction of Shelah will be reformulated using the PID to provide alternative models of the failure of CH and the existence of a universal colouring of cardinality. The impact of the range of the colourings will be examined. An application to the theory of strong colourings over partitions will also be given.

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• 2021 Jan 13

# Analysis seminar: Tracey Balehowsky (Helsinki) — An inverse problem for the relativistic Boltzmann equation

12:00pm to 1:00pm

In this talk, we consider the following problem: Given the source-to-solution map for a relativistic Boltzmann equation on a neighbourhood $V$ of an observer in a Lorentzian spacetime $(M,g)$ and knowledge of $g|_V$, can we determine (up to diffeomorphism) the spacetime metric $g$ on the domain of causal influence for the set $V$?