Résumés

Jon Aaronson (Tel-Aviv University)
Limit properties of infinite transformations and their return time stochastic processes.

This will be a review of some distributional and pointwise limit properties of some infinite transformations (and hence their return time stochastic processes) and - some new applications of the Darling-Kac method to ''weakly pointwise dual ergodic'' transformations yielding eg the stable limit theorems and (other) law of the iterated logarithm for certain positive statiionary processes (work in progress with Roland Zweimuller); -- a distributional limit theorem for transformations like the Hajian-Ito-Kakutani transformation (work in progress with Omri Sarig).

Oleg Ageev (Moscow State Technical University)
Typical homeomorphisms of Cantor sets; spectral invariants and embeddings into group actions.

Pierre Arnoux (Institut de Mathématiques de Luminy)
Tilings and endomorphisms of free groups.

We will give an overview of some recent progresses on self-similar tilings related to substitutions and endomorphisms of free groups, and on related dynamical systems.

Julien Brémont (Université Paris 12)
Random walk in quasi-periodic random environment

We consider a one-dimensional random walk with finite range in a random environment defined by an ergodic translation on a torus. For regular data and under a Diophantine condition on the translation, we prove an invariance principle with deterministic centering.

Jean-Pierre Conze (Université de Rennes)
Examples of stationary walks over rotations: recurrence, regularity.

We will give different examples of noncompact recurrent extensions of rotations. In particular, we discuss recurrence/transience for extensions of bi-dimensional rotations (joint work with Nicolas Chevallier)

Sylvain Crovisier (Université Paris 13)
Realization of minimal and uniquely ergodic homeomorphisms on manifolds.

In a joint work with F. Beguin and F. Le Roux, we prove that the family of measured dynamical systems which can be realised as uniquely ergodic minimal homeomorphisms on a given manifold (of dimension at least two) is stable under measured extension. As a corollary, any ergodic system with an irrational eigenvalue is isomorphic to a uniquely ergodic minimal homeomorphism on the two-torus. The proof uses realization techniques by Rees and the following improvement of Weiss relative version of Jewett-Krieger theorem: any extension between two ergodic systems is isomorphic to a skew-product on Cantor sets.

Fabien Durand (Université de Picardie)
Eigenvalues of finite topological rank Cantor dynamical systems.

Krzysztof Frączek (University of Toruń)
Growth and mixing

My talk will be based on a joint paper with Leonid Polterovich. Given a bi-Lipschitz measure-preserving homeomorphism of a compact metric space (with a probability Borel measure) of finite dimension, consider the sequence formed by the Lipschitz norms of its iterations. I shall discuss the growth of this sequence for some classes of homeomorphisms. For homeomorphisms which mix Lipschitz functions I shall present some universal lower estimations on the growth and some lower bounds which depend on the rate of mixing.

Houcein El Abdalaoui (Université de Rouen)
On the spectral type of the Funny rank one maps.

Andres del Junco (Toronto)
Almost continuous orbit equivalence for groups of homeomorphisms.

Anatole Katok (Penn State University)
What are the theorems in ergodic theory?

The meaning of this question is the following. What are non-trivial results which either hold for all measure-preserving transformations or for broad classes such as ergodic or weakly mixing? Behind this question is an underlying concern that the central notions of measure preserving transformation and measurable isomorphism of those, while great as a shorthand, are too vague to capture general properties, somewhat similarly to the notions of Banach space or a bounded linear operator in a Hilbert space. So what are they? There are venerable classics such as Birkhoff Ergodic Theorem, or von Neumann Pure Point Spectrum Theorem. Somewhat closer to our time one thinks of Furstenberg Multiple Weak Mixing Theorem (weak mixing implies multiple weak mixing) and subsequent developments identifying various characteristic factors. Beautiful characterizations of Bernoulli and standard/loosely Bernoulli systems qualify too. But what for example can be said about spectral properties of ergodic measure preserving transformations beyond von Neumann Theorem, invariance of the continuous spectrum under translations by the eigenvalues and density of the maximal spectral type? There is a vast and valuable body of work here which can be summarized by a generic statement: ``No, this is possible''. In other words, those results are not really theorems in the sense described above, but rather counterexamples. In this talk I will mention some of the most interesting counterexamples, give my prognosis about few outstanding old questions (Theorems or counterexamples?) and speculate both about the general issues and about few potential theorems.

Andrey Kochergyn (Moscow)
Mixing properties for some atypical flows on surfaces.

The talk discusses special flows over the circle rotations on atypical angles with logarithmic roof-function.

Mariusz Lemańczyk (University of Toruń)
On Parreau's theorem on non-mixing transformations

Martine Queffélec (Université de Lille 1)
M_0-measures for orthonormal systems

If T denotes the compact group $\R/\Z and µ is a complex measure on $\T$ identified to [0,1), the Fourier coefficients of µ are defined by $$\hat\mu(n)=\int_\T e^{-2i\pi nt} d\mu(t),\ n\in\Z.$$ The space $M_0(\T)$ consists in the complex measures on $\T$, whose Fourier coefficients tend to 0 at infinity. These measures appear in the characterization of the strong mixing property. Our interest in $M_0$-measures can also be explained by the role that they play in metric number theory and uniform distribution problems. We are thus looking forward to weaker hypotheses on measures ensuring some weaker normality properties; accordingly, that led us to consider other bounded orthonormal systems than characters and the behaviour of the related Fourier coefficients of measures. In particular, we shall focus on the Walsh system and compare both asymptotic behaviours of measures. This is a common work with François Parreau.

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Thierry de la Rue (Université de Rouen)
A Class of pairwise-independent Joinings

We introduce a special class of pairwise-independent self-joinings for a stationary process: Those for which one coordinate is a continuous function of the two others. We investigate which properties on the process the existence of such a joining entails. In particular, we prove that if the process is aperiodic, then it has positive entropy. Our other results suggest that such pairwise independent, non-independent self-joinings exist only in very specific situations: Essentially when the process is a subshift of finite type topologically conjugate to a full-shift. This provides an argument in favor of the conjecture that 2-fold mixing implies 3-fold-mixing.

Dalibor Volný (Université de Rouen)
Skew products with uncountable eigenvalue groups