Events & Seminars

2019 Mar 14

Manuel Luethi (ETH) : Effective equidistribution of primitive rational points along long horocycle orbits and disjointness to Kloosterman sums

10:00am to 11:30am

Location: 

Ross 70
Abstract: An observation by Jens Marklof shows that the primitive rational points of a fixed denominator along the periodic unipotent orbit of volume equal to the square of the denominator equidistribute inside a proper submanifold of the modular surface. This concentration as well as the equidistribution are intimately related to classical questions of number theoretic origin. We discuss the distribution of the primitive rational points along periodic orbits of intermediate size. In this case, we can show joint equidistribution with polynomial rate in the modular surface and in the torus.
2019 Apr 03

Analysis Seminar: Malte Gerhold (Technion) "Dilations of q-commuting unitaries"

12:00pm to 1:00pm

Location: 

Ross 70
Title:
Dilations of q-commuting unitaries
Abstract:
Let (u,v) be a pair of unitary operators on a Hilbert space H such that vu=quv for a complex number q of modulus 1. For q' another complex number of modulus 1, we determine the smallest constant c>0 for which there exists a pair of q' commuting unitaries (U,V) on a larger Hilbert space K containing H such that (u,v) is the compression of (cU,cV) to H.
2019 Mar 19

T&G: Viatcheslav Kharlamov (Strasbourg), Segre indices, Welschinger weights, and an invariant signed count of real lines on real projective hypersurfaces

1:00pm to 2:30pm

Location: 

Room 110, Manchester Building, Jerusalem, Israel
As it was observed a few years ago, there exists a certain signed count of real lines on real projective hypersurfaces of degree 2n+1 and dimension n that, contrary to the honest "cardinal" count, is independent of the choice of a hypersurface, and by this reason provides, as a consequence, a strong lower bound on the honest count. Originally, in this invariant signed count the input of a line was given by its local contribution to the Euler number of an appropriate auxiliary universal vector bundle.
2019 May 14

Dynamics Seminar: Rene Ruhr (Technion) Counting Saddle Connection on Translation surfaces.

2:00pm to 3:00pm


Abstract:
A collection of polygons with the property that to each side one can find another side parallel to it can be endowed with a translation surface structure by glueing along those edges.
This means that the closed surfaces obtained carries a flat metric outside finitely many conical singularities. Geodesics (which are straight lines) connecting such singularities are called saddle connections.
2019 Apr 30

Dynamics Seminar: Iftach Dayan (TAU) "Random walks on the 1-dim torus and an application to normal numbers on fractals"

2:15pm to 3:15pm

Location: 

Ross 70
Abstract: We show that under certain conditions, a random walk on the 1-dim torus by affine expanding maps has a unique stationary measure. We then use this result to show that given an IFS of contracting similarity maps of the real line with a uniform contraction ratio 1/D, where D is some integer > 1, under some suitable condition, almost every point in the attractor of the given IFS (w.r.t. a natural measure) is normal to base D.
2019 May 01

Set Theory Seminar - Thomas Gilton (UCLA): Abraham-Rubin-Shelah Open Coloring Axiom with a large continuum

2:00pm to 3:30pm

Location: 

Ross 63

Abstract: In their 1985 paper, the above three authors introduced a consistent generalization of Ramsey's theorem to pairs of countable ordinals, which we abbreviate as $OCA_{ARS}$. This axiom asserts that for any continuous coloring (with respect to an appropriate topology) of pairs of countable ordinals, there is a decomposition of $\omega_1$ into countably-many homogeneous sets. The key to their argument is to construct Preassignments of Colors.
2019 Mar 13

Set Theory Seminar - Tom Benhamou (TAU), "Projections of Tree-Prikry forcing"

2:00pm to 3:30pm

Location: 

Ross 63

Title: Projections of Tree-Prikry forcing.
Abstract:
Gitik, Kanovei and Koepke proved that if U is a normal measure over \kappa then the projections of Prikry forcing with U is essentially Prikry forcing with U.
The questions remains regarding to the Tree-Prikry forcing. Gitik and B. showed that without normality, it is possible that a Tree-Prikry generic sequence adds a Add(\kappa,1)
generic function.
In this talk we wish to examine which forcing notions can be projections of Tree-Prikry forcing under different large cardinals assumptions.
2019 Mar 27

Set Theory Seminar - Ralf Schindler (Munster), "Paradoxical" sets with no well-ordering of the reals

2:00pm to 3:30pm

Location: 

Ross 63
Title: "Paradoxical" sets with no well-ordering of the reals
Abstract: By a Hamel basis we mean a basis for the reals, R, construed as a vecor space over
the field of rationals. In 1905, G. Hamel constructed such a basis from a well-ordering
of R. In 1975, D. Pincus and K. Prikry asked "whether a Hamel basis exists in any
model in which R cannot be well ordered." About two years ago, we answered this positively
in a joint paper with M. Beriashvili, L. Wu, and L. Yu. In more recent joint
2019 Mar 20

Set Theory Seminar - Tom Benhamou (TAU) (part II)

2:00pm to 3:30pm

Location: 

Ross 63

Title: Projections of Tree-Prikry forcing.
Abstract:
Gitik, Kanovei and Koepke proved that if U is a normal measure over \kappa then the projections of Prikry forcing with U is essentially Prikry forcing with U.
The questions remains regarding to the Tree-Prikry forcing. Gitik and B. showed that without normality, it is possible that a Tree-Prikry generic sequence adds a Add(\kappa,1)
generic function.
In this talk we wish to examine which forcing notions can be projections of Tree-Prikry forcing under different large cardinals assumptions.
2019 Mar 12

Dynamics Seminar: Terry Soo (KU) Finitary isomorphism of Bernoulli flows

2:15pm to 3:15pm

Location: 

Ross 70
A powerful theory due to Ornstein and his collaborators has been successfully applied to many random systems to show that they are isomorphic to independent and identically distributed systems. The isomorphisms provided by Ornstein's theory may not be finitary, that is, effectively realizable in practice. Despite the large number of systems known to be Bernoulli, there are only a handful of cases where explicit finitary isomorphisms have been constructed. In this talk, we will discuss classical and recent constructions, and some long standing open problems.
2019 May 22

Analysis seminar: Yoel Grinshpon "Fluctuations of linear statistics for Schroedinger operators with a random decaying potential"

12:00pm to 1:00pm

Location: 

Ross 70
Title:
Fluctuations of linear statistics for Schroedinger operators with a random
decaying potential
Abstract:
Linear statistics provide a tool for the analysis of fluctuations of random
measures and have been extensively studied for various models in random
matrix theory. In this talk we discuss the application of the same
philosophy to the analysis of the finite volume eigenvalue counting measure
of one dimensional Schroedinger operators and demonstrate it with some
interesting results in the case of a random decaying potential.

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