The Budapest  Wien Dynamics seminar
This is a series of seminars initiated to foster
exchange between the
very dynamical ergodic theory groups based in Vienna and
Budapest.
Organizers: Henk Bruin, Peter Balint
Upcoming
events:
 13 March 2020 , University of Vienna:
An afternoon of jolly good talks about this and that, plus an even better evening.

14:15  15:15: Viviane Baladi (Paris): On the measure of maximal entropy of Sinai billiards.
Abstract: Sinai billiards maps and flows are uniformly hyperbolic  however
grazing orbits give rise to singularities. Most existing works on the ergodic properties
of billiards are about the SRB measure (i.e. the Liouville measure in the case of flows),
for which exponential mixing is known (both in discrete and continuous time). Another
natural equilibrium state is the measure of maximal entropy. Since the discretetime
billiard is discontinuous, the mere existence of this measure is not granted a priori.
With Mark Demers, under a mild condition of sparse recurrence to the singularities,
we have recently constructed a measure of maximal entropy and shown that it is unique,
Bernoulli and has full support. I will also discuss conditions ensuring that the measure
of maximal entropy differs from the SRB measure.
 15:30  16:30: Imre Peter Toth (Budapest): Nonintegrability in circular billiards.
Abstract: At the 2019 Sydney workshop on mathematical billiards, Sonia
PintodeCarvalho
proposed the question whether there is a surface where
the geodesic circular billiard is not
integrable. In other words,
consider a 2dimensional Riemannian manifold M and a domain D
in M such
that the boundary of D is a circle. Now consider a point particle which
moves in D
with unit velocity along geodesics until it hits the
boundary, where it gets reflected elastically.
The resulting dynamical
system  the circular billiard  is clearly fully integrable when M is
the
Euclidean plane or a sphere. But can it also be nonintegrable?
In this talk I present a positive answer by constructing many examples
of nonintegrable
circular billiards, and ask some further questions
about even more possible examples. This is
joint work with Alexey Glutsyuk.
 17:00  18:00: Tomas Persson (Lund): Recurrence.
Abstract: Recurrence is a classical topic in ergodic theory.
Poincaré's recurrence theorem
(Carathéodory, 1919) says that under
some conditions, $d(x,T^n x)$ becomes arbitrarily
small for almost
all points $x$, that is allmost all points returns arbitrarily
close to themself.
Another classical result is by Boshernitzan
(1993). It is a more quantitative version of
Poincaré's recurrence
theorem, and says that if $s$ is the Hausdorff dimension of the
space,
then, for almost all $x$, $d(x,T^n x)$ is approximately
$n^{1/s}$ or smaller for infinitely
many $n$.
In this talk, I will present some new results on recurrence obtain
in collaboration with
Maxim Kirsebom and Philipp Kunde. For some
interval maps and linear maps on tori, we
obtained refined scales
of recurrence rates compared to Boshernitzan's result. In a very
general
setting, we have also proved a ''uniform'' version of
Boshernitzan's result.
Projected events: Tentative
dates for subsequent meetings: 8 May 2020 ,
Past events:
 31 Jan 2020 , Budapest University of Technology and Economics (local information here):

Karoly Simon (BME Budapest): Appropriate dimensional Hausdorff measure of typical selfsimilar and selfconformal attractors on the line.
 Zoltan
Buczolich (Budapest): Fast and slow points of Birkhoff sums.
 Olli Hella (Helsinki): Stein's method for dynamical systems.
 8 Nov 2019 , Budapest University of Technology and Economics (local information here):

Balazs Barany (Budapest): Superexponential condensation without exact overlaps.
 Dalia Terhesiu (Leiden): Rates of mixing for the Lorenz gas.
 Maik Gröger (U Vienna): Bifurcation sets from families of bounded orbits, open dynamics and matching.
 27 Sept 2019 , University of Vienna:

Toru Sera (Kyoto): A conditional limit theorem for the PomeauManneville map.
 Tanja Schindler (Australian National University, SNS Pisa):
Strong laws under trimming  a comparison between iid random variables and dynamical systems.
 Jon Aaronson (Tel Aviv): On mixing of infinite measure preserving transformations.
 3 May 2019, Budapest University of Technology and Economics (local information here):
 Mike Todd (U of St.Andrews): Escape rates for multimodal maps with holes.
 Nandor
Simanyi (Birmingham, AL): Asymptotic homotopic complexity of 2D dispersing
billiards.
 Domokos
Szasz (Budapest): Andras Kramli (19432019).
 5 April 2019, University of Vienna:
 Abel Farkas (Renyi Institute): Interval projections of selfsimilar sets.
 Peter Balint (BME Budapest): Marked length spectrum and the geometry of open dispersing
billiards.
 Maja Resman (U Zagreb): Formal classification of powerlogarithmic germs and fractal approach.
 1 March 2019, Budapest University of Technology and Economics (local information here):
 Karoly Simon (BME Budapest): Hausdorff dimension for som nonMarkovian repellers.
 Maik Gröger (U Vienna): Amorphic complexity, substitution subshifts and iterated function systems.
 Henk Bruin (U Vienna): Limit laws for almost Anosov flows.
 25 January 2019, University of Vienna:
 Karoly Simon (BME Budapest): Hausdorff dimension of some nonconformal attractors.
 Sascha Troscheit (U Vienna): Selfconformal sets with positive Hausdorff measure.
 Benjamin Vejnar (Prague): Complexity of the homeomorphism relation between compact spaces.
 9 November 2018, Budapest University of Technology and Economics (local information here):
 Michal Rams (Impan Warsaw): Badly approximable numbers for irraional rotation.
 Feliks Przytycki (Impan Warsaw): Geometric coding trees for iterations of rational maps.
 Alejandro Kocsard (Univ Federal Fluminense): The Burnside problem for groups of diffeomorphisms.
 20 September 2018, University of Vienna:
 Dalia Terhesiu (Exeter): Mixing for some Zextensions of suspension flows.
 Balazs Barany (Budapest): Dimension of planar selfaffine measures with application to Birkhoff and Lyapunov spectra.
 Gabriel Fuhrmann (Imperial College): Unique ergodicity and zero entropy of irregular symbolic extensions of irrational rotations.
 27 April 2018, Budapest
University of Technology and Economics (local information here):
 Karoly Simon (BME Budapest): Hausdorff dimnsion for triangular selfaffine IFS.
 Alexey Korepanov (Exeter): Strength of strong approximation with a Brownian motion.
 Thomas
Gilbert (Brussels): The stochastic LotkaVolterra predatorprey model: it keeps cycling on!
 2 March 2018, University of Vienna:
 Manos Zafeiropoulos (Graz): Inhomogeneous Diophantine Approximation on M_0 sets.
 Balazs Barany
(Budapest): Almost multiplicativity of planar matrix cocycles and the difference between quasiBernoulli and Gibbs measures.
 Benoit Kloeckner (Paris Est): Optimal transportation, transfer operators and decay of correlations.
 20 Dec 2017, Budapest
University of Technology and Economics (local information here):

Fanni Selley
(BME Budapest): Stability of the invariant distribution in infinite systems of coupled maps.
 Françoise
Pène (Brest): Stochastic properties of the Z^{2} periodic Sinai billiard.
 Benoit
Saussol (Brest): Spatiotemporal Poisson process for visits to small sets in hyperbolic dynamics.
 20 Oct 2017, University of Vienna:

Jun Luo (Chongqing University): Lipschitz equivalence of selfsimilar fractals.
 Michal Rams (Warsaw): Lyapunov spectra of matrix cocycles.
 Nandor
Simanyi (Birmingham, AL): Noncommutative Rotation Vectors for Certain Cylindrical Billiards.
 30 June 2017, Budapest
University of Technology and Economics (local information here):

Peter Kevei (University od Szeged): On the tail of the solution of random fixed point equations.
 Henk Bruin (U Vienna): Regular variation for almost Anosov diffeomorphism.
 Mike Todd (U of St.Andrews): Analysis of a transient interval map.
 28 April 2017, University of Vienna:

Sonja
Stimac (University of Zagreb): Lozilike maps.
 Fanni Selley
(BME Budapest): Coupled map systems with a continuum of sites.
 Stefano Marmi (SNS Pisa): Small divisors and interval exchange maps.
 3 Mar 2017, Budapest
University of Technology and Economics (local information here):

Karoly Simon (BME Budapest): Singularity of selfsimilar measures.
 Thomas Jordan (Bristol): Selfaffine sets and Assouad dimension.
 Vadim Kaloshin (Maryland & ETH): Birkhoff conjecture for convex planar billiards
and deformational spectral rigidity of planar domains.
 26 Jan 2017, University of Vienna:
 Jiri Cerny (U Vienna): Maximum of Branching Random Walk in Random Environment.
 Imre Peter Toth (Budapest):
Rare interaction limit and the evolution of unstable
manifolds in a deterministic heat conduction model.
 9 Dec 2016, University of Vienna:
 Henk Bruin (U Vienna): Return time statistics: varying limits.
 Peter Balint (BME Budapest): Improved upper bound on the rate of mixing for the map of two falling balls.
 28 Oct 2016, Budapest
University of Technology and Economics:
 Karoly Simon (Budapest): Hausdorff dimension of certain selfaffine attractors.
 Michal Rams (Warsaw): Inhomogneous Diophantine Approximations.
 Roland Zweimüller (Vienna): Poisson limits for rare events in probability preserving systems.
 8 Apr 2016, ESI
Vienna,
part of thematic
programme
 Maciej Wojtkowski
(Opole): Integrable
and chaotic Gaussian thermostats on some
homogeneous spaces.
 Jozef Bobok
(Prague): (Quasi)similarity
of polygonal billiards.
 Balazs Barany
(Budapest): LedrappierYoung
formula and exact dimensionality of selfaffine
measures.
 26 Feb 2016, Budapest
University of Technology and Economics:
 Zoltan
Buczolich (Budapest): Convergence of ergodic averages
for many group rotations.
 Henk
Bruin (Vienna): Sharp mixing
rates via inducing w.r.t. general return times.

4 Dec 2015, Budapest
University of Technology and Economics:
 Alexey
Korepanov (Warwick):
Linear response for
intermittent maps with summable and nonsummable
decay of correlations.
 Roland
Zweimüller (Vienna): Functional
stable and related limit theorems for (some)
dynamical systems.
 Imre Peter
Toth (Budapest): Equidistribution for singular
measures in planar dispersing billiard flows.

2 Oct 2015, ESI Vienna,
final day of workshop:
An
afternoon of jolly good talks about this and that, plus an
even better evening!
 Feliks
Przytycki (IMPAN, Warsaw):
Geometric pressure in real and
complex 1d dynamics via trees of preimages and via
spanning sets.
 Fanni Selley
(BME Budapest): Mean field
coupling of identical expanding circle maps.
 Mariusz
Urbanski (Univ of Texas at Denton): Random dynamics of transcendental
meromorphic functions.
 29 May
2015, University of Vienna:
 Andras Nemedy Varga
(Budapest): The flow of two
falling balls mixes rapidly.
 Simon
Rechberger (Vienna): On the relation of return and
hitting time limits in infinite ergodic systems.
 Ian Morris
(Surrey): The transfer
operator for the binary Euclidean algorithm.
 24
April 2015, Budapest
University of Technology and Economics:
 Zemer
Kosloff (Warwick): Conservative Anosov maps on the
2torus without absolutely continuous invariant
measures.
 Thomas
Gilbert (Brussels): Multistate Lévy walks to describe the
kinetics of diffusive processes combining ballistic
motion.
 Vadim
Kaimanovich (Ottawa): Stopping times and Poisson
boundaries.
 27
March 2015, University of Vienna:
 Michael Tsiflakos
(Vienna): N falling balls
are globally ergodic.
 Lajos Vágó
(Budapest): A
parametrized family of refinement
equations and applications to projections of
generalized fractal percolations.
 Viviane
Baladi (DMA ENS Paris): The
spectrum of Sinai billiard flows.

27 Feb 2015, Budapest
University of Technology and Economics:
 Atahualpa
S. Kraemer (Düsseldorf): On
the free path lengths distribution for quasiperiodic
Lorentz gases.
 Mike
Todd (St Andrews): Dynamical
systems with holes: slow mixing cases.
 Stefano
Luzzatto (ICTP Trieste): SRB measures for partially hyperbolic
systems whose central direction is weakly expanding.

12 Dec 2014, University
of Vienna:
 Henk Bruin
(Vienna): A renewal
scheme for nonuniformly hyperbolic semiflows II.
On tail estimates of cropped transfer operators.
 Istvan
Berkes (Graz): Irrational
rotations, GCD sums and the Khinchin conjecture.
 Benoit
Saussol (Brest): Exponential
law for random subshifts of finite type.
 14 Nov 2014, Budapest
University of Technology and Economics:
 István
Kolossváry (Budapest):
On the local Hölder exponents
of deRhamlike fractal curves.
 Françoise
Pène (Brest): Asymptotic
poissonity of the number of visits to small balls.

17 Oct 2014, University
of Vienna:

Pawel
Pilarczyk (IST Austria): Perception of transitivity and
mixing at finite resolutions.
 Dalia
Terhesiu (Vienna): A renewal scheme for nonuniformly
hyperbolic flows.
 Carl
Dettmann (Bristol): Stickiness
in mushroom billiards.

19 Sept 2014, Budapest
University of Technology and Economics:
 Zsolt
PajorGyulai (Maryland): From
averaging to homogenization in cellular flows an
exact description of the transition.
 Roland
Zweimüller (Vienna): Return
and hittingtime limits for rare events in infinite
measure preserving systems.
 Domokos
Szasz & Peter Balint
(Budapest): On the work of
Nicolai Chernov.
 13
June 2014, University of Vienna:
 Peyman Eslami
(Rome): Decay of
correlations for skew products with discontinuities.
 Mohammad
Soufi (ICTP Trieste): Statistical stability for the
geometric Lorenz attractor.
 Stefano
Galatolo (Pisa): Rigorous
computing of the invariant measure in Lorenz like
systems.
 8 May
2014, Budapest
University of Technology and Economics:
 Nandor
Simanyi (Birmingham, AL): The BoltzmannSinai hypothesis: A
mystery solved.
 Tamas Tel
(Budapest): Absorbing
billiards and other dynamical systems.
 Oscar
Bandtlow (London): Hölder
continuity of the topological entropy for expanding
interval maps with holes.
 7 March
2014, University of Vienna:
 Damien
Thomine (Rennes): Local time and first return
time of periodic semiflows.
 Domokos
Szasz (Budapest): Local
ergodicity  a survey.
 20
September 2013,
University of Vienna:
 Karoly
Simon (Budapest): Slices
of generalized Sierpinski carpets.
 Tobias
Jäger (Dresden): Minimal
set of torus homeomorphisms.
 Evgeny
Verbitskiy (Leiden): Expansivity and homoclinic points in
algebraic dynamics.
 24 May 2013, Budapest University of Technology
and Economics:
 Mark
Demers (Fairfield): Perturbations of
dispersing billiards via spectral methods.
 Zoltan
Buczolich (Budapest): Averages
along the squares and related topics.
 12 April
2013,
University of Vienna:
 Dalia
Terhesiu
(Rome): Mixing for some nonuniformly
hyperbolic systems with infinite measure.
 Marta
TyranKaminska (Katowice):
Continuous time random
walks and limit theorems.
 Roland
Zweimüller (Vienna): Stochastically stable globally coupled
maps with bistable thermodynamic limit.
 1 March 2013, Budapest University of Technology
and Economics:
 Klaus
Schmidt (Vienna): Entropy
and periodic points for (commuting) group
automorphisms.
 Peter
Nandori (Budapest): Lorentz
process with shrinking holes in a wall.
 25 Jan
2013,
University of Vienna:
 Peter Balint
(Budapest): Limit laws
and convergence of moments for dispersing billiards
with cusps.
 Carlangelo
Liverani (Rome): Statistical
properties of maps close to a trivial extension.
 Gerhard
Keller (Erlangen): Stability
index for chaotically driven concave maps.
 14 Dec
2012,
Budapest University of Technology
and Economics:
 Roland
Zweimüller (Vienna): Dissipative dynamics as a tool for
conservative systems.
 Imre
Peter Toth (Budapest): Complexity of singularities and
growth of unstable manifolds in planar dispersing
billiards with corner points.
 23 Nov 2012, University of Vienna:
 Oliver
Butterley (Vienna): Operator semigroups associated to
continuous time dynamical systems.
 Peter
Nandori (Budapest): On
Dettmann's "horizon"conjectures.
 Ian
Melbourne (Warwick): Convergence
of fastslow ODEs and maps to stochastic differential
equations with multiplicative noise.
 21 Sept 2012, Budapest University of Technology
and Economics:
 Henk
Bruin (Vienna):
Thermodynamics for
Lebesgue dissipative interval maps.
 Pablo
Shmerkin (Surrey): Continuity of subadditive Pressure.
Last
update: 2 Feb 2020