2019
May
13

# Events & Seminars

2019
May
14

# Dynamics Lunch: Hongming Nie "Preperiodic points of unicritial polynomials”.

12:00pm to 1:00pm

Following the paper “ Preperiodic points and unlikely intersection” by Baker and DeMarco.

2019
May
13

# NT & AG Lunch: Michael Temkin "Elliptic curves with complex multiplication, II"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

We'll talk about explicit class field theory of imaginary quadratic fields

2019
May
13

# NT & AG Seminar: "A dream desingularization algorithm", Michael Temkin (HU)

2:30pm to 4:00pm

## Location:

Ross 70

Abstract: Any birational geometer would agree that the best algorithm

for resolution of singularities should run by defining a simple invariant of

the singularity and iteratively blowing up its maximality locus.

The only problem is that already the famous example of Whitney umbrella

shows that this is impossible, and all methods following Hironaka had

to use some history and resulted in more complicated algorithms.

Nevertheless, in a recent work with Abramovich and Wlodarczyk we did

for resolution of singularities should run by defining a simple invariant of

the singularity and iteratively blowing up its maximality locus.

The only problem is that already the famous example of Whitney umbrella

shows that this is impossible, and all methods following Hironaka had

to use some history and resulted in more complicated algorithms.

Nevertheless, in a recent work with Abramovich and Wlodarczyk we did

2019
May
28

# Dynamics seminar: Toru Sera (Kyoto) "Multidimensional arcsine law for intermittent interval maps"

2:00pm to 3:00pm

Abstract:

Paul L\'evy's classical arcsine law states that the occupation time ratio of one-dimensional Brownian motion for the positive side is arcsine-distributed. The arcsine law has been generalized to a variety of classes of stochastic processes and dynamical systems.

Paul L\'evy's classical arcsine law states that the occupation time ratio of one-dimensional Brownian motion for the positive side is arcsine-distributed. The arcsine law has been generalized to a variety of classes of stochastic processes and dynamical systems.

2019
Jun
10

# NT & AG Seminar - Dan Edidin - ``An intrinsic characterization of cofree representations of reductive groups''

1:00pm to 2:00pm

## Location:

Ross 70

Title: An intrinsic characterization of cofree representations of reductive groups

2019
May
07

# Anatoly Vershik (St. Petersburg) Соmbinatorial (locally finite) еncoding of the Bernoulli processes with infinite entropy.

2:00pm to 3:00pm

Abstract.

The realization of m.p automorphisms as transfer on the space of the

paths on the graded graphs allows to use new kind of encoding

of one-sided Bernoulli shift.

I will start with simple example how to realize Bernoulli shift in

the locally finite space (graph) $\prod_n {1,2,\dots n}$ (triangle

compact.)

Much more complicated example connected to old papers by

S.Kerov-Vershik and recent by Romik-Sniady in which one-sided

Bernoulli shift is

realized as Schutzenberger transfer on the space of infinite Young

The realization of m.p automorphisms as transfer on the space of the

paths on the graded graphs allows to use new kind of encoding

of one-sided Bernoulli shift.

I will start with simple example how to realize Bernoulli shift in

the locally finite space (graph) $\prod_n {1,2,\dots n}$ (triangle

compact.)

Much more complicated example connected to old papers by

S.Kerov-Vershik and recent by Romik-Sniady in which one-sided

Bernoulli shift is

realized as Schutzenberger transfer on the space of infinite Young

2019
Jun
27

# Group and dynamics seminar: Michael Chapman (HUJI): Cutoff on Ramanujan complexes

10:00am to 11:15am

## Location:

Ross 70

Abstract: A Markov chain over a finite state space is said to exhibit the total variation cutoff phenomenon if, starting from some Dirac measure, the total variation distance to the stationary distribution drops abruptly from near maximal to near zero. It is conjectured that simple random walks on the family of $k$-regular, transitive graphs with a two sided $\epsilon$ spectral gap exhibit total variation cutoff (for any fixed $k$ and $\epsilon). This is known to be true only in a small number of cases.

2019
Jun
03

# Combinatorics - back to back:

11:00am to 1:00pm

## Location:

CS Rothberg bldg, room B-500, Safra campus

First talk:

Speaker: Madeleine Weinstein (Berkeley)

Title: Voronoi Cells of Varieties

Abstract:

Speaker: Madeleine Weinstein (Berkeley)

Title: Voronoi Cells of Varieties

Abstract:

2019
May
13

# Combinatorics: Shira Zerbib (U. Michigan, Iowa State University) "Envy-free division of a cake without the “hungry players" assumption"

11:00am to 1:00pm

## Location:

CS bldg, room B-500, Safra campus

Speaker: Shira Zerbib (U. Michigan, Iowa State University)

Title: Envy-free division of a cake without the “hungry players" assumption

Abstract:

The fair division theorem due to Stromquist (1980) ensures that under some conditions it is possible to divide a rectangular cake into n pieces and assign one piece to each of n players such that no player strictly prefers a piece that has not been assigned to him.

Title: Envy-free division of a cake without the “hungry players" assumption

Abstract:

The fair division theorem due to Stromquist (1980) ensures that under some conditions it is possible to divide a rectangular cake into n pieces and assign one piece to each of n players such that no player strictly prefers a piece that has not been assigned to him.

2019
May
06

# Combinatorics: Omri Ben Eliezer (TAU) "Finding patterns in permutations"

11:00am to 1:00pm

## Location:

CS building, room B-500, Safra campus

Speaker: Omri Ben Eliezer, TAU

Title: Finding patterns in permutations

Abstract:

For two permutations sigma and pi, we say that sigma contains a copy of

pi, if there is a subset (not necessarily consecutive) of elements in sigma,

whose relative order is the same as in pi. For example, if pi = (1,2,3),

then a copy of pi in sigma amounts to an increasing subsequence in sigma

of length 3.

As shown by Guillemot and Marx, a copy of a constant length pi can be

found in sigma in linear time. However, how quickly can one find such a

Title: Finding patterns in permutations

Abstract:

For two permutations sigma and pi, we say that sigma contains a copy of

pi, if there is a subset (not necessarily consecutive) of elements in sigma,

whose relative order is the same as in pi. For example, if pi = (1,2,3),

then a copy of pi in sigma amounts to an increasing subsequence in sigma

of length 3.

As shown by Guillemot and Marx, a copy of a constant length pi can be

found in sigma in linear time. However, how quickly can one find such a

2019
May
16

# Basic Notions: Ehud de Shalit (HUJI) " Hilbert's 12th problem - recent developments"

4:00pm to 5:15pm

## Location:

Ross 70

Hilbert's 12th problem (Kronecker's Jugendtraum) is one of the major open problems

2019
Jun
10

# Combinatorics: Eyal Karni (BIU) "Combinatorial high dimensional expanders"

11:00am to 1:00pm

## Location:

CS bldg, room B-500, Safra campus

Speaker: Eyal Karni (BIU)

Title: Combinatorial high dimensional expanders

Abstract:

An eps-expander is a graph G=(V,E) in which every set of vertices X where |X|<=|V|/2 satisfies |E(X,X^c)|>=eps*|X| . There are many edges that "go out" from any relevant set.

Title: Combinatorial high dimensional expanders

Abstract:

An eps-expander is a graph G=(V,E) in which every set of vertices X where |X|<=|V|/2 satisfies |E(X,X^c)|>=eps*|X| . There are many edges that "go out" from any relevant set.

2019
May
27

# Combinatorics: Uri Rabinovich (U. Haifa) "SOME EXTREMAL PROBLEMS ABOUT SIMPLICIAL COMPLEXES"

11:00am to 1:00pm

## Location:

CS Rothberg bldg, room B-500, Safra campus

Speaker: Uri Rabinovich (U. Haifa)

Title: SOME EXTREMAL PROBLEMS ABOUT SIMPLICIAL COMPLEXES

Abstract:

We shall discuss the following three issues:

* The existence of Hamiltonian d-cycles, i.e., simple d-cycles containing a spanning d-hypertree of a complete d-complex K_n^d;

* The existence of a distribution D over spanning d-hypertrees T of K_n^d, so that for ANY

(d-1)-cycle C there, the expected size of the d-filling of C with respect to a random T from D is Omega(n^d);

Title: SOME EXTREMAL PROBLEMS ABOUT SIMPLICIAL COMPLEXES

Abstract:

We shall discuss the following three issues:

* The existence of Hamiltonian d-cycles, i.e., simple d-cycles containing a spanning d-hypertree of a complete d-complex K_n^d;

* The existence of a distribution D over spanning d-hypertrees T of K_n^d, so that for ANY

(d-1)-cycle C there, the expected size of the d-filling of C with respect to a random T from D is Omega(n^d);

2019
May
23

# Basic Notions: Ehud de Shalit (HUJI) " Hilbert's 12th problem - recent developments"

4:00pm to 5:15pm

## Location:

Ross 70

Hilbert's 12th problem (Kronecker's Jugendtraum) is one of the major open problems