2019 Nov 19

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

2:00pm to 3:00pm

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


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


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.

2020 Jan 01

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

12:00pm to 1:00pm


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.
2019 Nov 05

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

2:00pm to 3:00pm

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.
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