2019 Oct 31

# Groups & Dynamics seminar - Vincent Guirardel (Universite de Rennes 1) "Measure Equivalence rigidity for Out(Fn)"

10:00am to 11:00am

## Location:

Ross 70
Abstract:
Measure equivalence of countable groups is a measure theoretic analogue
of quasi-isometry.
For example, any two lattices in the same Lie group are by definition
measure equivalent.
We prove that any countable group that is measure equivalent to Out(Fn)
is virtually isomorphic to Out(Fn). This is a joint work with Camille
Horbez.
2019 Oct 29

# Zemer Kosloff, Finitary isomorphisms of Brownian motions

2:00pm to 3:00pm

Ornstein and Shields (Advances in Math., 10:143-146, 1973) proved that Brownian motion reflected on a bounded region is an infinite entropy Bernoulli flow and thus Ornstein theory yielded the existence of a measure-preserving isomorphism between any two such Brownian motions. For fixed h >0, we construct by elementary methods, isomorphisms with almost surely finite coding windows between Brownian motions reflected on the intervals [0, qh] for all positive rationals q. This is joint work with Terry Soo.
2019 Nov 26

2:00pm to 3:00pm

Ross 70

2019 Nov 19

# Tom Meyerovitch (BGU), Efficient finitary codings by Bernoulli processes

2:00pm to 3:00pm

Abstract:
Recently Uri Gabor refuted an old conjecture stating that any
finitary factor of an i.i.d process is finitarly isomorphic to an
i.i.d process. Complementing Gabor's result,
in this talk, which is based on work in progress with Yinon Spinka,
we will prove that any countable-valued process which is admits a
finitary a coding by some i.i.d process furthermore admits an
$\epsilon$-efficient finitary coding, for any positive $\epsilon$.
Here an $\epsilon$-efficient coding'' means that the entropy
2019 Oct 31

# Basic Notions: Gil Kalai (HUJI) "Classical and quantum computation"

4:00pm to 5:15pm

## Location:

Ross 70
In the lecture I will describe basic notions of computational complexity:
Boolean functions, basic algorithmic tasks, Boolean circuits, P, NP, randomness, quantum circuits, noisy quantum circuits, bounded depth circuits, and more.
If time permits I will describe some (or more realistically one) mathematical challenge in the field and briefly
describe some examples (more realistically, one example) on how theory meets reality.
2019 Nov 20

# Eshnav: Mike Hochman - The isoperimetric inequality

6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)

פרופ' מייק הוכמן: האי-שוויון האיזופרימטרי

האי-שוויון האיזופרימטרי קובע שמבין כל הגופים בעלי נפח 1 במרחב אוקלידי N-מימדי, הגוף בעל שטח הפנים הקטן ביותר הוא כדור. יתר על כן, גוף קמור מנפח 1 ששטח פניו קרוב לשטח הפנים של כדור קרוב בעצמו, במובן מתאים, להיות כדור. לטענה זו יש היסטוריה ארוכה והיא היתה מוכרת, בגירסה זו או אחרת, כבר בימי קדם, אך הוכחה מלאה ניתנה רק בסוף המאה ה-19 ותחילת המאה ה-20, והכללות שלה מעסיקות מתמטיקאים עד היום.

2019 Dec 25

# Analysis Seminar: Adi Glucksam (Toronto) "Optimal growth of frequently oscillating subharmonic functions"

12:00pm to 1:00pm

## Location:

Ross 70

Title: Optimal growth of frequently oscillating subharmonic functions.

Abstract: In this talk I will present Nevanlinna-type tight bounds on the minimal possible growth of subharmonic functions with a large zero set.  We use a technique inspired by a paper of Jones and Makarov.
2019 Dec 03

# Uri Gabor (HUJI) - A measurable-group-theoretic solution to von Neumann’s problem (following D. Gaboriau and R. Lyons)

12:00pm to 1:00pm

2020 Jan 14

2:00pm to 3:00pm

2019 Nov 12

# Uri Gabor (HUJI), On the failure of Ornstein's theory in the finitary category.

2:00pm to 3:00pm

Abstract: In this talk, I'll show the invalidity of finitary counterparts for three main theorems in classification theory: The preservation of being a Bernoulli shift through factors, Sinai's factor theorem, and the weak Pinsker property. This gives a negative answer to an old conjecture and to a recent open problem.
2019 Oct 29

# Hagai Lavner (HUJI) - A Short Proof of Bernoulli Disjointness via the Local Lemma following ANTON BERNSHTEYN

12:00pm to 1:00pm

2019 Nov 06

# Analysis Seminar: Eyal Seelig (HUJI) "On the spacing of zeros of paraorthogonal polynomials for singular measures"

12:00pm to 1:00pm

## Location:

Ross 70
Title: On the spacing of zeros of paraorthogonal polynomials for singular measures
Abstract:
2020 Jan 01

# Analysis Seminar: Cyril Tintarev (Uppsala, visiting Technion) "Weak convergence methods: Cocompactness and structured defect of compactness" )

12:00pm to 1:00pm

## Location:

Ross 70
Profile decomposition theorem is a refinement of the Banach-Alaoglu (weak compactness) theorem in presence of a given set of quasi-isometries. We define a class of co-compact embeddings of Banach spaces that yields a clear structure for bounded divergent sequences. This is a generalization, on the functional-analytic level, of the concentration compactness principle of Lions. Applications include Sobolev, Jawerts  Strichartz and Moser-Trudinger embeddings.
2020 Jan 21

# Sebastian Barbieri (Bordeaux) On the relation between topological entropy and asymptotic pairs

2:00pm to 3:00pm

Abstract: I will present some results that state that under certain
topological conditions, any action of a countable amenable group with
positive topological entropy admits off-diagonal asymptotic pairs. I
shall explain the latest results on this topic and present a new
approach, inspired from thermodynamical formalism and developed in
collaboration with Felipe García-Ramos and Hanfeng Li, which unifies all
previous results and yields new classes of algebraic actions for which
2019 Nov 05

# Or Landesberg, On Radon measures invariant under horospherical flows on geometrically infinite quotients

2:00pm to 3:00pm

Abstract:
We consider a locally finite (Radon) measure on SO(d,1)/Gamma
invariant under a horospherical subgroup of SO(d,1) where Gamma is a discrete, but not necessarily geometrically finite, subgroup. We show that whenever the measure does not observe any additional invariance properties then it must be supported on a set of points with geometrically degenerate trajectories under the corresponding contracting 1-parameter diagonalizable flow (geodesic flow). This is joint work with Elon Lindenstrauss.