Eventss

2019 Dec 10

Boris Solomyak (BIU) Hoelder regularity for the spectrum of translation flows

2:00pm to 3:00pm


Abstract: We consider generic translation flows corresponding to Abelian differentials on flat surfaces of genus $g\ge 2$. These flows are weakly mixing by the Avila-Forni theorem. Recently Forni obtained Hoelder estimates on spectral measures for almost all translation flows, following earlier work by Bufetov and myself in genus two. Combining Forni's idea with our methods, we extended our proof to the case of arbitrary genus $g\ge 2$. It is based on a vector form of the Erd\H{o}s-Kahane argument, which I will try to explain.
This is a joint work with A. Bufetov.
2019 Oct 30

Logic Seminar - Eugenio Colla

11:00am to 1:00pm

Location: 

Ross 63
Model-theoretic proofs of partition theorems for semigroups.


Abstract: 
Partition theorems have the following form. Let "regular" be some notion for a structure S; theorem: for every finite partition of S there is a "regular" set inside a cell of the partition. 
2019 Nov 05

T&G: Andrei Caldararu (UW Madison), A survey of categorical enumerative invariants

1:00pm to 2:30pm

Location: 

Room 209, Manchester Building, Jerusalem
I will survey recent progress in defining and computing categorical enumerative invariants, analogues of Gromov-Witten invariants defined directly from a cyclic A_infinity category and a choice of splitting of the Hodge filtration on its periodic cyclic homology. A proposed definition of such invariants appeared in 2005 in work of Costello, but the original approach had technical problems that made computations impossible.
2019 Nov 07

Basic Notions: Wayne Horowitz (HUJI, Archaeology department) "Some themes in Babylonian Mathematics of Astronomy".

4:00pm to 5:15pm

Location: 

Ross 70
Today, in our modern world, we perceive the physical universe in mathematical terms; whether degrees on longitude and latitude on earth, or in units of space-time beyond our earthly horizons. This talk will present two ancient cuneiform tablets from Babylonia which offer a geometric impression of the physical world as experienced by ancient Babylonians. Comparisons will be made with a range of other ancient mathematical, geographic, and astronomical materials from the cuneiform Ancient Near East.
2019 Nov 07

Groups & Dynamics seminar: Alex Margolis (Technion) “Almost normal subgroups and quotient spaces״

10:00am to 11:00am

Location: 

Ross 70
Abstract: A subgroup is said to be almost normal if it is commensurable
to all of its conjugates. Even though there may not be a well-defined
quotient group, there is still a well-defined quotient space that admits
an isometric action by the ambient group. We can deduce many geometric
and algebraic properties of the ambient group by examining this action.
In particular, we will use quotient spaces to prove a relative version
of Stallings-Swan theorem on groups of cohomological dimension one. We
2019 Nov 11

Combinatorics: Barak Weiss (TAU)

10:00am to 12:00pm

Location: 

C-400, CS building

Speaker: Barak Weiss (TAU)

Title:  New bounds on the covering radius of a lattice.

Abstract:

We obtain new upper bounds on the minimal density of lattice coverings of R^n by dilates of a convex body K. We also obtain bounds on the probability (with respect to the natural Haar-Siegel measure on the space of lattices) that a randomly chosen lattice L satisfies L + K = R^n. As a step in the proof, we utilize and strengthen results on the discrete Kakeya problem. This is joint work with Or Ordentlich and Oded Regev. 

Pages