“Infinite measure dynamics”
June, 6th to 9th 2017, UBO, Brest, France.

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Tuesday 6 Wednesday 7 Thursday 8 Friday 9

J. Chaika
R. Dougall

E. Roy

S. Brofferio
J. Aaronson
M. Bromberg
D. Thomine

A. Málaga S.

University canteen Water tower University canteen University canteen

F. Dal’bo
O. Glorieux

D. Terhesiu
Walk by the sea
D. Dolgopyat
S. Gouëzel

Walk by the sea

Walk by the sea
M. Stadlbauer


1 Short talks by young researchers.


Jon Aaronson (Univ. Tel Aviv)       Sara Brofferio (Univ. Paris Sud)
Michael Bromberg (Univ. Bristol)       Jon Chaika (Univ. Utah)
Françoise Dal’bo (Univ. Rennes 1)       Dmitri Dolgopyat (Univ. Maryland)
Rhiannon Dougall (Univ. Warwick)       Olivier Glorieux (IMPA)
Sébastien Gouëzel (Univ. Nantes)       Alba Málaga Sabogal (Univ. Paris 8)
Emmanuel Roy (Univ. Paris 13)       Manuel Stadlbauer (Univ. Rio de Janeiro)
Dalia Terhesiu (Univ. Vienna)       Damien Thomine (Univ. Paris Sud)
Roland Zweimüller (Univ. Vienna)      

Practical informations

The conference takes place in Brest, France. The city is located by the sea, the air temperature is between 18 and 28 Celsius degree, the water temperature is between 16 and 18 degree and there are no mosquitos. The beaches are located outside the city and are better reached by bus/car, a trip is planned on wednesday afternoon.

Directions to the university

Concerning transportation, tickets can be purchased at stations and in buses but not in tramways. The same ticket works for buses, tramways and telepherique (1 hour duration) and must be stamped each time you enter a vehicle.

From the airport

The airport is located North-East of the city. Either take a taxi (15 mn, 30 euros) or take the shuttle in front of the airport. Shuttle tickets (1.5 euros) are purchased in the shuttle. The shuttle goes to the tramway terminus station (10 mn) or to the railway station. The tramway goes to the center of the town (30 mn). Get off at place de la liberté. This is the city center, from which you can reach the university or your hotel in at most 15 minutes, either by bus or by foot.

From the city center

The university can be reached from the town center or the railway station by bus (15mn) or by foot (30mn). Take the bus number 1 either in front of the railway station or from place de la liberté. Tickets can be bought on the bus. Wait until the bus takes a huge blue bridge and get off at Bouguen close to entry A of the faculté des Sciences, just after the roundabout. A detailed map of the bus stations is available on the website of the Bibus bus company.

On the campus

The mathematics department is located on third floor of the bâtiment C, the building closest to entry A. The secretary is in the library, close to the restroom and the coffee machine. The talks take place in Amphitheater E.


Annick Nicolle is the secretary of the research laboratory.

email:, phone number: +33 (0) 2 98 01 62 07.

The local organizers are Yves Coudène and Françoise Pène.

Brest airport
Airport shuttle
Railway (SNCF)
Brest Bus
University location
Math department


Jon Aaronson (Univ. Tel Aviv)

Kamel Belarif (UBO)

Adrien Boulanger (Univ. Paris 6)

Sara Brofferio (Univ. Paris Sud)

Michael Bromberg (Univ. Bristol)

Jon Chaika (Univ. Utah)

Jean-Pierre Conze (Univ. Rennes)

Yves Coudène (UBO)

Gilles Courtois (UPMC)

Françoise Dal’bo (Univ. Rennes 1)

Nguyen Thi Dang (Univ. Rennes 1)

Jean-Marc Derrien (UBO)

Yves Derriennic (UBO)

Aziz El Hadji Abdou Diop (Dakar)

Dmitry Dolgopyat (Univ. Maryland)

Rhiannon Dougall (Univ. Warwick)

Olivier Glorieux (IMPA)

Sébastien Gouëzel (Univ. Nantes)

Lingmin Liao (Univ. Paris-Est Créteil)

François Maucourant (Univ. Rennes 1)

Thi Hien Nguyen (UBO)

Jean-Claude Picaud (Univ. Tours)

Françoise Pène (UBO)

Anja Randecker (Univ. Toronto)

Emmanuel Roy (Univ. Paris 13)

Alba Málaga Sabogal (Univ. Paris 8)

Adamou Saidou (Univ. Dan Dicko Dankoulodo de Maradi)

Benoit Saussol (UBO)

Barbara Schapira (Univ. Rennes 1)

Cesar Silva (Williams College)

Manuel Stadlbauer (Univ. Rio de Janeiro)

Samuel Tapie (Univ. Nantes)

Dalia Terhesiu (Univ. Vienna)

Damien Thomine (Univ. Paris Sud)

Nasab Yassine (UBO)

Hisatoshi Yuasa (Univ. Osaka Kyoiku)

Roland Zweimüller (Univ. Vienna)

Titles and abstracts of the talks

Jon Aaronson

Rational ergodicity properties and distributional limits of infinite ergodic transformations.

In infinite ergodic theory, various weak and distributional limits replace the absolutely normalized pointwise ergodic theorem. We’ll review the subject and then see that every random variable on the positive reals occurs as the distributional limit of some infinite ergodic transformation. As a corollary, we obtain a complete classification of the possible ”A-rational ergodicity properties” for an infinite ergodic transformation.

The main construction follows by ”inversion” from a cutting and stacking construction showing that every random variable on the positive reals occurs as the distributional limit of the partial sums of some positive, ergodic stationary process normalized by a 1-regularly varying normalizing sequence (indeed, here the process can be chosen over any EPPT).

Joint work with Benjamin Weiss. See arXiv:1604.03218

Sara Brofferio

On unbounded invariant measures of stochastic dynamical systems

We consider stochastic dynamical systems Xn = Ψn(Xn-1), where Ψn are i.i.d. random continuous transformations of R. We assume that Ψn(x) behave asymptotically like Anx, for some random positive number An. The main example is the stochastic affine recursion Xn = AnXn-1 +Bn, but this class includes other interesting processes such as reflecting random walks or branching process. Our aim is to describe invariant Radon measures of the process {Xn} in the critical case, when E logA = 0. Under optimal assumptions, we prove that those measures behave at infinity like dx∕x. In the proof we strongly use some properties of random walks on the affine group. The talk will be based on a joint paper with Dariusz Buraczewski.

Michael Bromberg

Temporal distributional limit theorem for cocycles over rotations

For a measure preserving system (X,B,μ,T ) and a real valued function f on X, temporal random variables along an orbit of a fixed point x in X are obtained by considering the Birkhoff sums Sn(f,x), n = 1,...,N and choosing n randomly uniformly from 1, ..., N. These r.v’s, measure the fraction of time that Birkhoff sums spend in various sets. If, under proper normalization, as N tends to infinity, these variables converge to a non-atomic distribution, we say that f satisfies a temporal limit theorem along the orbit of x (when the limit is Gaussian, we refer to this as temporal CLT). The aim of the talk is to introduce the relevant concepts and sketch a proof of a temporal CLT for piecewise constant cocycles with a single breakpoint, over an irrational rotation with a badly approximable rotation number. This result generalises earlier results by J.Beck and by D.Dolgopyat and O.Sarig. This is joint work with C.Ulcigrai.

Jon Chaika

Ergodicity of typical skew products over some interval exchange transformations

Let T be a linear recurrent interval exchange transformation. This is a measure zero, but full Hausdorff dimension set of interval exchange transformations that are analogous to badly approximable rotations. We show that an R valued skew product over such an IET by an integral 0 function that is a linear combination of characteristic functions of intervals is typically ergodic. Relevant terms will be defined. This is joint work with Donald Robertson.

Françoise Dal’bo

An example of a nonuniform lattice with infinite Bowen-Margulis measure

Joint work with M.Peigné, J-C Picaud, A.Sambusetti.
I will explain how to construct a noncompact negatively curved Riemannian surface with finite volume admitting an infinite Bowen-Margulis measure.

Dmitry Dolgopyat

On Local Limit Theorems for hyperbolic flows

I describe an approach to proving local limit theorems and related for flows based on (multidimensional) local limit theorem for associated Poincare map. Both finite and infinite measure case will be discussed. Based on a joint work with Peter Nandori.

Rhiannon Dougall

Growth of closed geodesics for infinite covers

We are interested in the dynamics of the geodesic flow for infinite volume manifolds M which arise as a regular cover of a fixed compact (or convex cocompact) negatively curved manifold M0. Writing hM for the exponential growth rate of closed geodesics in M, we have that hM h0, where h0 is the topological entropy of the geodesic flow for M0. We answer the question of when there is a uniform gap hM < h0 in M in terms of the permutation representations given by the covering M of M0. The proof uses the symbolic dynamics for the flow, and so we formulate the analogous statements for countable state shifts obtained as group extensions of a finite state shift.

Olivier Glorieux

Hausdorff dimension and critical exponent of Quasi-Fuchsian Anti-de Sitter manifolds

The aim of my talk will be to explain how classical invariants and theorems for groups acting on the hyperbolic space, can be extended to the Anti-de Sitter (AdS) setting. We will recall the notion of critical exponent and Hausdorff dimension for discrete action on the hyperbolic space and explain how we can define similar notions for a certain type of groups acting on AdS manifolds. We will finally explain how to get a rigid bound for these invariants in dimension 3 which is a result equivalent a famous result obtained by R. Bowen in ’79 . This is a joint work with D. Monclair.

Sébastien Gouëzel

Quantitative Pesin theory for subshifts of finite type

In non-uniformly hyperbolic dynamics, Pesin sets are measurable sets where the dynamics is very well understood. However, their definition makes these sets hard to control in a quantitative way, even when the underlying dynamics is hyperbolic. We will explain why such a control is useful, and what kind of bounds we can obtain.
Joint work with L. Stoyanov.

Alba Málaga Sabogal


Emmanuel Roy

Ergodic splittings of Poisson processes

If N denotes a Poisson process, a splitting of N is formed by two point processes N1 and N2 such that N = N1 +N2. If N1 and N2 are independent Poisson processes then the splitting is said to be Poisson and such a splitting is always available (We allow the possibility to enlarge the ambient probability space). In general, a splitting is not Poisson but the situation changes if we require that the distributions of the point processes are invariant by a common underlying map that acts at the level of each point of the processes. We will prove that if this map has infinite ergodic index, then a splitting is necessarily Poisson if the environment is ergodic.

This is a work in progress, with Elise Janvresse and Thierry de la Rue.

Manuel Stadlbauer


Dalia Terhesiu

Exploiting semistable laws for i.i.d. random variables

We recall that semistable laws is a class of infinitely divisible laws, which complements the more well known stable laws. I will recall some main, previously established, results on necessary and sufficient conditions for the existence of semistable laws for i.i.d. random variables. I will report on work in progress with Peter Kevei which aims toward a complete understanding of a limit law for null recurrent renewal chains, assuming that the involved return function is in the domain of a semistable law (as such, no strict regular variation is required). Some analogies with the Darling Kac law will be discussed. If time remains, I will present some results of work in progress with Douglas Coates on semistable laws for interval intermittent maps.

Damien Thomine


Roland Zweimüller



The conference is funded by the following agencies:

l’université de Bretagne-Occidentale,

l’université Bretagne-Loire et la région Bretagne,

– le laboratoire de mathématiques de Bretagne Atlantique et le CNRS,

le groupement de recherche Platon,

l’institut universitaire de France,

le labex Lebesgue.

Yves Coudène, May 18, 2017