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 13

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

2:00pm to 4:00pm

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

# Logic Seminar - Krzysztof Krupinski

11:15am to 1:00pm

## Location:

https://huji.zoom.us/j/82821066522?pwd=aVJnTkxBYktycHdzNFN5WDV0R2FkZz09
On generating ideals by additive subgroups of rings and an application to
Bohr compactifications of some matrix groups

Abstract:
I will present several fundamental results about generating ideals in
finitely many steps inside additive groups of rings from my very recent
joint paper with T. Rzepecki. I will also mention an application to
computations of definable and classical Bohr compactifications of the
groups of upper unitriangular and invertible upper triangular matrices
2021 Jan 11

# AG & NT lunch: Francesco Maria Saettone "Gross' Canonical and Quasi-canonical Liftings"

1:00pm to 2:00pm

Date and time: 11 Jan, 2021, 13:00-14:00

Speaker:  Francesco Maria Saettone

Title:  Gross' Canonical and Quasi-canonical Liftings

Abstract: The goal of this talk is to give an account on Gross' seminal paper on canonical and quasi-canonical liftings of formal modules.
Except for basic notions on formal groups, this talk is intended to be self-contained.
2021 Jan 06

# Logic Seminar - Hanan Rabinowitz

11:15am to 1:00pm

## Location:

https://huji.zoom.us/j/82821066522?pwd=aVJnTkxBYktycHdzNFN5WDV0R2FkZz09
Results in Borel chromatic numbers using Infinite games and Borel determinacy

Abstract: (Based on the paper “A determinacy approach to Borel combinatorics” by Andrew Marks)
A Borel graph on a standard Borel space X is a symmetric irreflexive relation G on X that is Borel as a subset of X×X.

A Borel coloring of a Borel graph G on X is a Borel function c from X to a standard Borel space Y such that if
xGy then c(x)!=c(x)
2021 Jan 12

# Nachman Avraham-Reem (HUJI) The Orbit Equivalence Class of Markov SFT's

2:00pm to 3:00pm

Abstract: We discuss recent results on measure equivalence, orbit equivalence classification and Krieger type of Markov subshifts of finite type.
2021 Jan 04

# Mark Shusterman [HUJI-BGU Number Theory Seminar]

4:30pm to 6:00pm

The meeting will be open from 16.15 (local time) *NOTE UNUSUAL TIME* for a virtual coffee with the speaker.

Title: Short exponential sums and their applications over function fields

Abstract:

In joint work with Will Sawin, we obtain (square-root) cancellation in quite general incomplete exponential sums for the ring F_q[x] of polynomials over a finite field. This has applications to problems in analytic number theory such as the Chowla conjecture, Bateman-Horn conjecture, and the number of real quadratic function fields with a huge class group.
2020 Oct 19

# [HUJI-BGU Number Theory Seminar]

Repeats every week every Monday until Fri Jan 15 2021 except Mon Jan 04 2021.
2:30pm to 3:40pm

2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm
2:30pm to 3:40pm

## Location:

The meeting will be open from 14.15 (local time) for a virtual coffee with the speaker.

Join Zoom Meeting

Meeting ID: 815 6864 8940

Passcode: 3628800

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:
Join Zoom Meeting
Meeting ID: 837 2635 1672
Passcode: 7e288r
2021 Jan 12

# Zemer Kosloff (HUJI) Uniqueness of g-measures

12:00pm to 1:00pm

We will discuss the criteria for uniqueness of g-measures based on the theory of local absolute continuity of Kabanov-Lipcer and Shiryaev following Johansson, Oberg and Pollicott.

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Meeting ID: 815 9189 6783
Passcode: 4b941j
2020 Dec 30

# Logic Seminar - Daniel Palacin

11:15am to 1:00pm

## Location:

https://huji.zoom.us/j/82821066522?pwd=aVJnTkxBYktycHdzNFN5WDV0R2FkZz09

Solving equations in finite groups and complete amalgamation

Abstract: Roth's theorem on arithmetic progression states that a subset $A$ of the natural numbers of positive upper density contains an arithmetic progression of length 3, that is, the equation $x+z=2y$ has a solution in $A$.
2020 Dec 30

4:00pm to 6:00pm

First Talk: 16:00-17:00

Nachi Re'em: Markov measures

Abstract: We present measures on product spaces with Markovian type of dependence. We discuss questions like how they should be defined; in what way they are less understood than product measures; and, what nice properties of product measures we may hope to have also in Markov measures. We will assume knowledge in probability in an undergraduate level, as well as general familiarity with the fact that measures on product spaces can be specified on cylinders.
2021 Mar 22

# Combinatorics: Oliver Roche-Newton

11:00am to 1:00pm