2018 Jun 27

# Analysis Seminar: Barry Simon (Caltech) "Heinävarra’s Proof of the Dobsch–Donoghue Theorem"

12:00pm to 1:00pm

## Location:

Ross Building, Room 70
Abstract:
In 1934, Loewner proved a remarkable and deep theorem about matrix monotone functions. Recently, the young Finnish mathematician, Otte Heinävarra settled a 10 year old conjecture and found a 2 page proof of a theorem in Loewner theory whose only prior proof was 35 pages. I will describe his proof and use that as an excuse to discuss matrix monotone and matrix convex functions including, if time allows, my own recent proof of Loewner’s original theorem.
2018 May 29

# Yuri Lima (Paris 11): Symbolic dynamics for non-uniformly hyperbolic systems with singularities

2:15pm to 3:15pm

## Location:

Ross 70
Symbolic dynamics is a tool that simplifies the study of dynamical systems in various aspects. It is known for almost fifty years that uniformly hyperbolic systems have good'' codings. For non-uniformly hyperbolic systems, Sarig constructed in 2013 good'' codings for surface diffeomorphisms. In this talk we will discuss some recent developments on Sarig's theory, when the map has discountinuities and/or critical points, such as multimodal maps of the interval and Bunimovich billiards.
2018 May 08

# Dynamics Seminar: Yinon Spinka (TAU): Finitary codings of Markov random fields

2:15pm to 4:15pm

## Location:

Ross 70

Let X be a stationary Z^d-process. We say that X is a factor of an i.i.d. process if there is a (deterministic and translation-invariant) way to construct a realization of X from i.i.d. variables associated to the sites of Z^d. That is, if there is an i.i.d. process Y and a measurable map F from the underlying space of Y to that of X, which commutes with translations of Z^d and satisfies that F(Y)=X in distribution. Such a factor is called finitary if, in order to determine the value of X at a given site, one only needs to look at a finite (but random) region of Y.
2018 Apr 12

# Special talk: Yonatan Harpaz (Paris 13) - "Small extensions in algebra and topology"

## Lecturer:

Yonatan Harpaz (Paris 13)
1:15pm to 2:15pm

## Location:

Ross 70
Abstract: In this talk, we will discuss the notion of small extensions in its various incarnations, from torsors under abelian groups to square-zero extensions of algebras. We will then focus on the somewhat less familiar case of small extensions of ∞-categories. Our main goal is to make this abstract concept concrete and intuitive through a variety of examples. In particular, we will advocate the point of view that small extensions of  ∞-categories offer a unifying perspective in understanding many constructions appearing in obstruction, classification, and deformation theoretic problems
2018 Apr 16

# HD-Combinatorics Special Day on Grassman Expanders and Unique Games (organized by Irit Dinur)

(All day)

## Location:

Room 130, IIAS, Feldman Building, Givat Ram
2018 Apr 11

4:00pm to 6:00pm

Ross 70A
2018 Apr 15

# GAME THEORY AND MATHEMATICAL ECONOMICS RESEARCH SEMINAR: Ron Peretz, Bar Ilan University: "The Rate of Innovation Diffusion in Social Networks (joint with Itai Arieli, Yakov Babichenko, and Peyton H Young)"

1:30pm to 2:30pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
2018 May 22

# Dynamics Lunch: Tsviqa Lakrec (Huji)

12:00pm to 1:00pm

## Location:

Manchester lounge
2018 May 02

# Logic Seminar - Chloe Perin - "Forking in the free group"

12:00pm to 2:00pm

## Location:

Ross 63
Sela proved that the theory of free groups is stable. It is thus natural to wonder what the independence relation looks like. Together with Sklinos, we worked out a complete characterization of forking independence in the standard model (over any set of parameters) in terms of an algebraic-geometric object called the JSJ decomposition, which encodes all the splittings of the group as an amalgamated product or an HNN extension relative to the parameter set.
In the talk we will try to give an idea of the proof over some examples.
2017 Dec 06

# Logic Seminar - Daoud Siniora - "Automorphism groups of homogeneous structures"

11:00am to 1:00pm

## Location:

Math 209

A special class among the countably infinite relational structures is the class of homogeneous structures. These are the structures where every finite partial isomorphism extends to a total automorphism. A countable set, the ordered rationals, and the random graph are all homogeneous.
2018 May 01

# Logic Seminar - Asaf Karagila - "What can you say about critical cardinals?"

1:30pm to 3:30pm

## Location:

Math 209
We isolate the property of being a critical point, and prove some basic positive
properties of them. We will also prove a lifting property that allows lifting
elementary embedding to symmetric extensions, and outline a construction that
shows that it is consistent that a successor of a critical cardinal is singular.
This is a recent work with Yair Hayut.
2017 Mar 22

# Logic seminar - Chris Lambie-Hanson, "Trees with ascent paths"

4:00pm to 6:00pm

## Location:

Ross 70
Abstract: The notion of an ascent path through a tree, isolated by Laver, is a generalization of the notion of a cofinal branch and, in many cases, the existence of an ascent path through a tree provides a concrete obstruction to the tree being special. We will discuss some recent results regarding ascent paths through kappa-trees, where kappa > omega_1 is a regular cardinal. We will discuss the consistency of the existence or non-existence of a special mu^+-tree with a cf(mu)-ascent path, where mu is a singular cardinal.
2017 Apr 24

# Logic seminar

Repeats every week every Monday until Sun May 21 2017 except Mon May 01 2017.
12:00pm to 2:00pm

12:00pm to 2:00pm
12:00pm to 2:00pm

## Location:

Ross 63
We will take a close look at the first few steps of the construction of the Bristol model, which is a model intermediate to L[c], for a Cohen real c, satisfying V
eq L(x) for all x.
2018 Jun 27

# Logic Seminar - Shahar Oriel - "Erdos-Hajnal property for stable graphs"

11:00am to 1:00pm

## Location:

Ross 63
We will follow a short note by Artem Chernikov & Sergei Starchenko: "A note on the Erdos-Hajnal Conjecture."
“In this short note we provide a relatively simple proof of the Erd ̋os–Hajnal conjecture for families of finite (hyper-)graphs without the m-order property. It was originally proved by M. Malliaris and S. Shelah”
2017 Nov 22

# Logic Seminar - Yair Hayut - "Chang's Conjecture at many cardinals simultaneously"

11:00am to 1:00pm

## Location:

Math 209

Chang's Conjecture is a strengthening of Lowenheim-Skolem-Tarski theorem. While Lowenheim-Skolem-Tarski theorem is provable in ZFC, any instance of Chang's Conjecture is independent with ZFC and has nontrivial consistency strength. Thus, the question of how many instances of Chang's Conjecture can consistently hold simultaneously is natural.

I will talk about some classical results on the impossibility of some instances of Chang's Conjecture and present some results from a joint work with Monroe Eskew.