Eventss

2019 Dec 16

Combinatorics: Orit Raz (HUJI)

10:00am to 12:00pm

Location: 

C-400, CS building

Combinatorics Seminar HUJI


When: Monday Dec 16, 10:00-11:45
Where: C-400, CS building


Speaker: Orit Raz (HUJI)


Title: Dense graphs have rigid parts


Abstract:
2019 Dec 02

Combinatorics: Boaz Slomka (Open U.)

10:00am to 12:00pm

Location: 

C-400, CS building

Speaker: Boaz Slomka (Open U.)
Title: On Hadwiger's covering problem



Abstract:
A long-standing open problem, known as Hadwiger’s covering problem, asks what is the smallest natural number N(n) such that every convex body in R^n can be covered by a union of the interiors of N(n) of its translates. 

In this talk, I will discuss some history of this problem and its close relatives, and present more recent results, including a general upper bound for N(n).
2019 Dec 09

Combinatorics: Ilan Newman (Haifa)

10:00am to 12:00pm

Location: 

C-400, CS building

Speaker: Ilan Newman (Haifa)

Title:  Some recent results on sublinear algorithms for graph related properties

Abstract:
I will describe property testing of (di)graph properties in bounded degree graph models, and talk about a characterization of the 1-sided error testable monotone graph properties and the 1-sided error testable hereditary graph properties in this model. I will introduce the notion of configuration-free properties and talk about some graph theoretic open problems.
2019 Dec 05

Colloquium: Yoel Groman (HUJI) - Floer homology of the magnetic cotangent bundle

2:30pm to 3:30pm

Location: 

Manchester Building (Hall 2), Hebrew University Jerusalem

Hamiltonian Floer cohomology was invented by A. Floer to prove the Arnold conjecture: a Hamiltonian diffemorphism of a closed symplectic manifold has at least as many periodic orbits as the sum of the Betti numbers. A variant called Symplectic cohomology was later defined for certain non compact manifolds, including the  cotangent bundle of an arbitrary closed smooth manifold. The latter is the setting for classical mechanics of constrained systems.

2019 Nov 06

Logic Seminar - Itay Kaplan

11:00am to 1:00pm

Location: 

Ross building - Room 63
On distal and co-distal types

 

I will define the notions described in the title, and ask if they are equivalent. I will present a proof showing that they are in case the theory is NIP. The proof is essentially the proof of the fact that the lack of distality is witnessed by a sequence of singletons by Pierre Simon’s.
2019 Nov 04

NT & AG Lunch: Michael Temkin, "Resolution of singularities"

Repeats every week every Monday until Sun Dec 15 2019 .
1:00pm to 2:00pm

1:00pm to 2:00pm
1:00pm to 2:00pm
1:00pm to 2:00pm
1:00pm to 2:00pm
1:00pm to 2:00pm

Location: 

Mathematics, Faculty Lounge
This semester will be devoted to resolution of singularities -- a process that modifies varieties at the singular locus so that the resulting variety becomes smooth. For many years this topic had the reputation of very technical and complicated, though rather elementary.
In fact, the same resolution algorithm can be described in various settings, including schemes, algebraic varieties or complex analytic spaces.
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. 

Pages