Thick attractors, ergodic theorems for Hausdorff dimension, and Fubini regained.

Speaker: 

Yulij Ilyashenko

Institution: 

Cornell University, Independent University of Moscow, Moscow State University

Time: 

Tuesday, December 7, 2010 - 3:00pm

Location: 

RH 440R

The general belief is that attractors of diffeomorphisms of smooth manifolds either have measure zero, or coincide with the phase space. We prove that in the space of diffeomorphisms of a manifold with boundary onto itself there exists an open set (with at most a countable number of hypersurfaces deleted) such that any map from this set has a thick attractor: an attractor that has positive Lebesgue measure together with its complement. The result heavily relies upon the following two: ergodic theorems about the Hausdorff dimension of "exclusive" sets of some particular hyperbolic maps (P.Saltykov; Yu.Ilyashenko); overcoming of the "Fubini nightmare" for some perturbations of partially hyperbolic diffeomorphisms (joint work with A.Negut). Methods developed go back to investigations of A.Gorodetski and the speaker started at late 90's.

A brief survey of piecewise isometries in one dimension

Speaker: 

Scott Northrup

Time: 

Tuesday, November 23, 2010 - 3:00pm

Location: 

RH 440R

In this talk we we will first examine the dynamical properties of the simplest form of a piecewise isometry in one dimension, the interval exchange tranformation. We will then generalize this concept to interval translation mappings, and examine their dynamical properties, and consider an example of a rank 3 ITM which is of infinite type.

One dimensional quantum Ising model and hyperbolic dynamics

Speaker: 

William Yessen

Institution: 

UC Irvine

Time: 

Tuesday, October 12, 2010 - 3:00pm

Location: 

RH 440R

The one dimensional quantum Ising model is used in quantum statistical physics to model interracting particles on a discrete lattice. While the classical model (in one and two dimensions) has long been solved (its origin dates back to 1930's), its quasiperiodic analog (dating back about 25 years) is still a source of interesting problems. We shall discuss our solution to one such problem: we'll rigorously prove that the energy spectrum of the one dimensional quantum quasiperiodic Ising model is a Cantor set, as has been long believed, and discuss some of its properties.
This is the first in a series of two seminars dedicated to this topic. In this seminar we'll present the problem and set up the main ideas.

On conservative homoclinic bifurcations: recent results and open problems

Speaker: 

Anton Gorodetski

Institution: 

UC Irvine

Time: 

Tuesday, October 5, 2010 - 3:00pm

Location: 

RH 440R

In 1970s S.Newhouse discovered that a generic homoclinic bifurcation of a smooth surface diffeomorphism leads to persistent homoclinic tangencies, infinite number of attractors (or repellers), and other unexpected dynamical properties (nowadays called "Newhouse phenomena"). More than 20 years later P.Duarte provided an analog of these results in conservative setting (with attractors replaced by elliptic periodic points). We will discuss these and other recent results on conservative homoclinic bifurcations, and list some related open problems in the field.

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