Dynamical & Probability

The Dynamics & Probability Seminar meets every Tuesday at 14:15 at Ross 70.
The HUJI dynamics group webpage can be found here.

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 tableaux with Plancherel Measure. These examples open series of
2019 Mar 26

Dynamics Seminar: Nattalie Tamam "Diagonalizable groups with non-obvious divergent trajectories"

12:00pm to 1:00pm

Location: 

Manchester faculty club
Singular vectors are the ones for which Dirichlet’s theorem can be infinitely improved. For example, any rational vector is singular. The sequence of approximations for any rational vector q is 'obvious'; the tail of this sequence contains only q. In dimension one, the rational numbers are the only singulars. However, in higher dimensions there are additional singular vectors. By Dani's correspondence, the singular vectors are related to divergent trajectories in Homogeneous dynamical systems. A corresponding 'obvious' divergent trajectories can also be defined.
2019 Mar 07

Emmanuel Roy (Paris 13) Non-singular Poisson suspensions

2:45pm to 3:45pm

Location: 

Ross 70
Poisson suspensions are random sets of points endowed with a transformation that displaces each point according to a single transformation of the sigma-finite space where the points lie. In this ongoing work, instead of dealing with measure-preserving transformations (which is the classical case), we are going to present our attempt to explore the non-singular case. The difficulties are counterbalanced by new tools that are trivial in the measure-preserving case but highly informative in the non-singular one. We will present these tools as well as the first basic results we’ve obtained.
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 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 Mar 19

Dynamics Seminar: Elon Lindenstrauss (HUJI) - Double variational principle for mean dimension

2:15pm to 3:15pm

Mean dimension is a topological invariant of dynamical systems introduced by Gromov that measures the number of parameters per iteration needed to describe a trajectory in the system. We characterize this invariant (at least for dynamical systems with the marker property, such as infinite minimal systems) using a min-max principle, where choices of both a metric on the topological space and an invariant probability measure on the system are varied. The work I will report on is joint work with M. Tsukamoto.

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