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BEGIN:VEVENT
SUMMARY:Giovanni Panti (Università degli Studi di Udine)
DTSTART;VALUE=DATE-TIME:20210114T153000Z
DTEND;VALUE=DATE-TIME:20210114T164500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/1
DESCRIPTION:Title: Slo
w continued fractions\, Minkowski functions and the joint spectral radius<
/a>\nby Giovanni Panti (Università degli Studi di Udine) as part of Breme
n Online Dynamics Seminar\n\n\nAbstract\nEvery unimodular partition of the
real unit interval in m pieces gives\nrise to $2^m$ slow continued fracti
on maps. Many such maps have names\n(Farey fractions\, ceiling fractions\,
even/odd fractions\, ...)\, but most\nare nameless. Certain properties ar
e commonly shared (for example\, the\nvalidity of Lagrange's theorem)\, wh
ile other features are more delicate\n(the validity of the Serret theorem\
, the description of the unique a.c.\ninvariant measure\, the characteriza
tion of purely periodic points\, ...).\n\nAny slow continued fraction map
determines a Minkowski function\, namely\nthe distribution function of the
measure of maximal entropy. These\nMinkowski functions have a well-define
d average Holder exponent (studied\nby many authors\, and related to the d
imension of the measure)\, as well\nas a least Holder exponent. The latter
has the form log(m)/2*log(r)\,\nwith r a quadratic irrational\, the joint
spectral radius of the iterated\nfunction system given by the inverse bra
nches of the map.\n\nIt is plausible that every IFS with maps in $\\mathrm
{GL}(2\,\\mathbb Z)$ has algebraic joint\nspectral radius\, but as far as
we know this issue has not been settled.\nWe show however\, in joint work
with Davide Sclosa\, that this is indeed\nthe case for IFSs over two maps
in $\\mathrm{SL}(2\,\\mathbb Z_{\\geq 0})$.\n
LOCATION:https://researchseminars.org/talk/BODS/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Amir Mohammadi (UC San Diego)
DTSTART;VALUE=DATE-TIME:20210128T153000Z
DTEND;VALUE=DATE-TIME:20210128T164500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/2
DESCRIPTION:Title: Geo
desic planes in hyperbolic 3-manifolds\nby Amir Mohammadi (UC San Dieg
o) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nLet M be a hyp
erbolic 3-manifold\, a geodesic plane in M is a\ntotally geodesic immersio
n of the hyperbolic plane into M. In this talk\nwe will give an overview o
f some results which highlight how geometric\,\ntopological\, and arithmet
ic properties of M affect the behavior of\ngeodesic planes in M. This talk
is based on joint works with McMullen\,\nOh and Margulis.\n
LOCATION:https://researchseminars.org/talk/BODS/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Boris Springborn (TU Berlin)
DTSTART;VALUE=DATE-TIME:20201126T153000Z
DTEND;VALUE=DATE-TIME:20201126T164500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/3
DESCRIPTION:Title: The
hyperbolic geometry of Markov's theorem on Diophantine approximation and
quadratic forms\nby Boris Springborn (TU Berlin) as part of Bremen Onl
ine Dynamics Seminar\n\n\nAbstract\nMarkov's theorem classifies the worst
irrational numbers and the most non-zero quadratic forms. This talk is abo
ut a new proof using hyperbolic geometry. The main ingredients are a dicti
onary to translate between hyperbolic geometry and algebra/number theory\,
and some very\nbasic tools borrowed from modern geometric Teichmüller th
eory. Simple closed geodesics and ideal triangulations of the modular toru
s play an important role\, and so does the problem: How far can a straight
line crossing a triangle stay away from the vertices?\n
LOCATION:https://researchseminars.org/talk/BODS/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Laura Monk (IRMA\, Strasbourg)
DTSTART;VALUE=DATE-TIME:20201112T153000Z
DTEND;VALUE=DATE-TIME:20201112T164500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/4
DESCRIPTION:Title: The
geometry and spectrum of random hyperbolic surfaces\nby Laura Monk (I
RMA\, Strasbourg) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\
nThe main aim of this talk is to present geometric and spectral\npropertie
s of typical hyperbolic surfaces. More precisely\, I will:\n\n- introduce
a probabilistic model\, first studied by Mirzakhani\, which is\na natural
and convenient way to sample random hyperbolic surfaces\n\n- describe the
geometric properties of these random surfaces: diameter\,\ninjectivity rad
ius\, Cheeger constant\, Benjamini-Schramm convergence...\n\n- explain how
one can deduce from this geometric information estimates\non the number o
f eigenvalues of the Laplacian in an interval $[a\,b]$\,\nusing the Selber
g trace formula.\n
LOCATION:https://researchseminars.org/talk/BODS/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sören Petrat (Jacobs University)
DTSTART;VALUE=DATE-TIME:20200604T143000Z
DTEND;VALUE=DATE-TIME:20200604T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/5
DESCRIPTION:Title: Eff
ective Dynamics of the Mean-field Bose Gas\nby Sören Petrat (Jacobs U
niversity) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nThe qu
antum dynamics of N non-relativistic bosons is described\nby the Schroedin
ger equation with pair interaction. The complexity of\nsolutions generally
grow exponentially in the particle number\, so for\nlarge N coarse-graine
d or effective descriptions are desirable. From a\nmathematical physics po
int of view\, one aims at deriving effective\nequations in a rigorous way\
, i.e.\, proving that their solutions converge\nto the solutions of the Sc
hroedinger equation in a suitable topology. In\nthis talk\, we will consid
er the dynamics in the mean-field limit\, which\nhas been studied extensiv
ely in the last two decades. I will present an\noverview about the researc
h goals and results\, and then specifically\ndiscuss recent results of my
collaborators and myself on a perturbative\nexpansion of solutions to the
Schroedinger equation.\n
LOCATION:https://researchseminars.org/talk/BODS/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Keivan Mallahi-Karai (Jacobs University)
DTSTART;VALUE=DATE-TIME:20200702T143000Z
DTEND;VALUE=DATE-TIME:20200702T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/6
DESCRIPTION:Title: Loc
ally random groups\nby Keivan Mallahi-Karai (Jacobs University) as par
t of Bremen Online Dynamics Seminar\n\n\nAbstract\nGroups without non-triv
ial low dimensional representations\,\nnamed quasi-random by Gowers\, have
recently found many applications in\nstudying group theoretical problems
of combinatorial nature. Loosely\nspeaking\, non-existence of such repres
entations forces the product map\non the group mapping $(a\, b)$ to their
product $ab$ to have a certain mixing\nbehavior.\n\nIn this talk\, after b
riefly recalling the notion of quasi randomness\, I\nwill discuss a gener
alisation of this concept to the class of compact\ngroups. This property\,
called local randomness\, is formulated in terms\nof unitary representati
ons of the compact group $G$ and captures a similar\nmixing behavior at al
l scales. I will discuss a number of related\nresults including a classif
ication of locally random groups\, a mixing\ninequality\, and\, if time al
lows\, connection to spectral gap.\n\nThe talk is based on a joint work wi
th Amir Mohammadi and Alireza Salehi\nGolsefidy.\n
LOCATION:https://researchseminars.org/talk/BODS/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Mitchell (University of Birmingham)
DTSTART;VALUE=DATE-TIME:20210218T153000Z
DTEND;VALUE=DATE-TIME:20210218T164500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/7
DESCRIPTION:Title: Mea
sure theoretic entropy of random substitutions\nby Andrew Mitchell (Un
iversity of Birmingham) as part of Bremen Online Dynamics Seminar\n\n\nAbs
tract\nRandom substitutions and their associated subshifts provide\na mode
l for structures that exhibit both long range order and positive\nentropy.
In this talk we discuss the entropy of a large class of ergodic\nmeasures
\, known as frequency measures\, that arise naturally from random\nsubstit
utions. We introduce a new measure of complexity\, namely measure\ntheore
tic inflation word entropy\, and discuss its relationship to\nmeasure theo
retic entropy. We also show how this new measure of\ncomplexity can be us
ed to provide a framework for the systematic study\nof the measure theoret
ic entropy of random substitution subshifts.\n\nAs an application of our r
esults\, we obtain closed form formulas for the\nentropy of a wide range o
f random substitution subshifts and show that\nin many cases there exists
a frequency measure of maximal entropy.\nFurther\, for a class of random s
ubstitution subshifts\, we show that this\nmeasure is the unique measure o
f maximal entropy.\n\nThis is joint work with P. Gohlke\, R. Leek\, D. Rus
t\, and T. Samuel.\n
LOCATION:https://researchseminars.org/talk/BODS/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlangelo Liverani (U Roma „Tor Vergata“)
DTSTART;VALUE=DATE-TIME:20210209T130000Z
DTEND;VALUE=DATE-TIME:20210209T143000Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/9
DESCRIPTION:Title: Mea
surements in Dynamical Systems\nby Carlangelo Liverani (U Roma „Tor
Vergata“) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nVery
often a measurement of a physical system takes the form of a finite\ntime
average for some observable. For infinite time averages Birkhoff's\ntheore
m classifies all the possible outcomes in terms of the invariant\nmeasures
of the system. The study of the\, much more realistic\, finite\ntime aver
ages is equivalent to investigating at which speed the limit is\nattained.
This problem is only partially understood\, essentially we\nunderstand fe
w special cases. Yet\, our current knowledge shows that the\nbehaviour dep
ends drastically from the properties of the system. In the\nstudy of such
a problem functional analysis\, probability theory\, and\ngeometry play ma
jor roles. I will attempt to give an overview of the\nsubject.\n\nThis is
a joint event with the mathematical colloquium at the\nUniversity of Breme
n\n
LOCATION:https://researchseminars.org/talk/BODS/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Barbara Schapira (Université Rennes 1)
DTSTART;VALUE=DATE-TIME:20210315T143000Z
DTEND;VALUE=DATE-TIME:20210315T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/10
DESCRIPTION:Title: St
rong positive recurrence for geodesic flows\nby Barbara Schapira (Univ
ersité Rennes 1) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\
nIn a recent paper with S Gouezel and S Tapie\, in the context of geodesic
\nflows of noncompact negatively curved manifolds\, we propose three\ndiff
erent definitions of entropy and pressure at infinity\, through\ngrowth of
periodic orbits\, critical exponents of Poincaré series\, and\nentropy (
pressure) of invariant measures. We show that these notions\ncoincide. Tha
nks to these entropy and pressure at infinity\, we\ninvestigate thoroughly
the notion of strong positive recurrence in this\ngeometric context. A po
tential is said strongly positively recurrent\nwhen its pressure at infini
ty is strictly smaller than the full\ntopological pressure. We show in par
ticular that if a potential is\nstrongly positively recurrent\, then it ad
mits a finite Gibbs measure. We\nalso provide easy criteria allowing to bu
ild such strong positively\nrecurrent potentials and many examples.\n\nDur
ing the talk\, I will present some of these points\, to give to the\naudie
nce the flavour of this work.\n
LOCATION:https://researchseminars.org/talk/BODS/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Péter Koltai (FU Berlin)
DTSTART;VALUE=DATE-TIME:20210419T133000Z
DTEND;VALUE=DATE-TIME:20210419T144500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/11
DESCRIPTION:Title: Co
arse-graining of transport in non-autonomous systems\nby Péter Koltai
(FU Berlin) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nThe
decomposition of the state space of a dynamical system into almost\ninvari
ant sets is important for understanding its essential macroscopic\nbehavio
r. The concept is reasonably well understood for autonomous\ndynamical sys
tems\, and recently a generalization appeared for\nnon-autonomous systems:
coherent sets. Aiming at a unified theory\, in\nthis talk we will first p
resent connections between the\nmeasure-theoretic autonomous and non-auton
omous concepts. We shall do\nthis by considering the augmented state space
. Second\, we will extend\nthe framework to finite-time systems\, and show
that it is especially\nwell-suited for manipulating the mixing properties
of the dynamics.\nThird\, we will show how this framework can be used to
identify the birth\nand death of coherent sets.\n
LOCATION:https://researchseminars.org/talk/BODS/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valérie Berthé (CNRS\, IRIF\, Université de Paris)
DTSTART;VALUE=DATE-TIME:20210531T133000Z
DTEND;VALUE=DATE-TIME:20210531T144500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/12
DESCRIPTION:Title: Mu
ltidimensional continued fractions and symbolic codings of toral translati
ons\nby Valérie Berthé (CNRS\, IRIF\, Université de Paris) as part
of Bremen Online Dynamics Seminar\n\n\nAbstract\nIt has been a long standi
ng problem to find good symbolic codings for\nKronecker toral translatio
ns that enjoy the beautiful properties\nof Sturmian sequences like low fa
ctor complexity and good local\ndiscrepancy properties. \nWe construct suc
h codings in terms of multidimensional continued fraction\nalgorithms that
are realized by sequences of substitutions. In particular\,\ngiven any st
rongly convergent continued fraction algorithm\, these sequences\nlead to
renormalization schemes which produce symbolic codings and bounded\nremain
der sets at all scales in a natural way. Such sets \nprovide particular
ly strong convergence properties of ergodic sums\, \nand are also closel
y related to the notion of balance in word\ncombinatorics. \n As strong c
onvergence of a continued fraction algorithm results in a Pisot\ntype prop
erty\, our approach provides a systematic way to confirm purely\ndiscrete
\nspectrum results for wide classes of substitutions.\nThis is joint wor
k with W. Steiner and J. Thuswaldner.\n
LOCATION:https://researchseminars.org/talk/BODS/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ilya Gekhtman (Technion)
DTSTART;VALUE=DATE-TIME:20210308T143000Z
DTEND;VALUE=DATE-TIME:20210308T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/13
DESCRIPTION:Title: Gi
bbs measures vs. random walks in negative curvature\nby Ilya Gekhtman
(Technion) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nThe id
eal boundary of a negatively curved manifold naturally\ncarries two types
of measures.\nOn the one hand\, we have conditionals for equilibrium (Gibb
s) states\nassociated to Hoelder potentials\; these include the Patterson-
Sullivan\nmeasure and the Liouville measure. On the other hand\, we have s
tationary\nmeasures coming from random walks on the fundamental group.\n
We compare and contrast these two classes.First\, we show that both\nof t
hese of these measures can be associated to geodesic flow invariant\nmeasu
res on the unit tangent bundle\, with respect to which closed\ngeodesics s
atisfy different equidistribution properties. Second\, we show\nthat the a
bsolute continuity between a harmonic measure and a Gibbs\nmeasure is equi
valent to a relation between entropy\, (generalized)\ndrift and critical
exponent\, generalizing previous formulas of\nGuivarc’h\, Ledrappier\, a
nd Blachere-Haissinsky-Mathieu. This shows that\nif the manifold (or more
generally\, a CAT(-1) quotient) is geometrically\nfinite but not convex co
compact\, stationary measures are always singular\nwith respect to Gibbs m
easures.\nA major technical tool is a generalization of a deviation inequa
lity due\nto Ancona saying the so called Green distance associated to the
random\nwalk is nearly additive along geodesics in the universal cover.\nP
art of this is based on joint work with Gerasimov-Potyagailo-Yang and\npar
t on joint work with Tiozzo.\n
LOCATION:https://researchseminars.org/talk/BODS/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giulio Tiozzo (University of Toronto)
DTSTART;VALUE=DATE-TIME:20210322T143000Z
DTEND;VALUE=DATE-TIME:20210322T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/14
DESCRIPTION:Title: Th
e fundamental inequality for random walks on cocompact Fuchsian groups
\nby Giulio Tiozzo (University of Toronto) as part of Bremen Online Dynami
cs Seminar\n\n\nAbstract\nSeveral stochastic processes are defined on the
hyperbolic plane H^2. For instance\, one can consider a Brownian motion\,
or a discretized version thereof\, when one performs a random walk on the
group of isometries of H^2. \n\nIt is a recurring question\, going back to
Furstenberg\, Guivarc’h\, Ledrappier\, Kaimanovich\, and others\, \nwhe
ther the measures obtained from the random walks coincide with measures of
geometric origin\, such as the Lebesgue measure. \n\nWe prove that the hi
tting measure is singular with respect to Lebesgue measure for any random
walk on a cocompact Fuchsian group generated by translations on opposite s
ides of a symmetric hyperbolic polygon. This addresses a question of Kaima
novich-Le Prince. \n\nJoint with P. Kosenko.\n
LOCATION:https://researchseminars.org/talk/BODS/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rhiannon Dougall
DTSTART;VALUE=DATE-TIME:20210517T133000Z
DTEND;VALUE=DATE-TIME:20210517T144500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/15
DESCRIPTION:Title: Co
mparison of entropy for infinite covering manifolds\, and group extensions
of subshifts of finite type\nby Rhiannon Dougall as part of Bremen On
line Dynamics Seminar\n\n\nAbstract\nA classical example of an Anosov flow
is the geodesic flow associated to\na compact hyperbolic manifold M\, for
which the periodic orbits of the\nflow correspond to closed geodesics in
M. In general\, Anosov flows are\nnot so well behaved: there may be infini
tely many periodic orbits in a\nfree homotopy class\, in contract to geode
sic flows. In this talk we\ndiscuss the problem of counting periodic orbit
s in infinite covering\nmanifolds\, where we relate the exponential growth
rate of periodic\norbits in the cover to properties of the covering group
. One of the\ntools is a new result for non-symmetric group extensions of
subshifts of\nfinite type which includes a result on non-symmetric random
walks. I\nwill spend some time motivating the problems and give the perspe
ctive of\nthe thermodynamical formalism.\n(Featuring joint work with Richa
rd Sharp.)\n
LOCATION:https://researchseminars.org/talk/BODS/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ilka Agricola (Uni Marburg)
DTSTART;VALUE=DATE-TIME:20210608T140000Z
DTEND;VALUE=DATE-TIME:20210608T151500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/16
DESCRIPTION:Title: Wh
at are spinors and what should they be?\nby Ilka Agricola (Uni Marburg
) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nRichard Dedekin
d published in 1888 a paper entitled "Was sind und was sollen\ndie Zahlen?
"\, variously translated as "What are numbers and what should\nthey be?".
In analogy to this classic\, I shall investigate in this talk\nwhat spinor
s (or\, in full term\, spinor fields) are\, what distinguishes\nthem from
functions\, how they appear naturally in complex analysis and\ntheoretical
physics\, and\, finally\, why they are an object of intrinsic\nmathematic
al\ninterest. Doing so\, I will give a gentle introduction to spin geometr
y\nand Dirac operators for the non-experts\, and I will provide an overvie
w of\ntypical problems and interesting links to other areas.\n\nThis is a
joint seminar with the University of Bremen Mathematics Colloquium.\n
LOCATION:https://researchseminars.org/talk/BODS/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vlad Vicol (NYU)
DTSTART;VALUE=DATE-TIME:20210506T140000Z
DTEND;VALUE=DATE-TIME:20210506T151500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/17
DESCRIPTION:Title: Sh
ock formation for the 3d Euler equations\nby Vlad Vicol (NYU) as part
of Bremen Online Dynamics Seminar\n\n\nAbstract\nIn this talk\, I will dis
cuss the shock formation process for the 3d\ncompressible Euler equations\
, in which sounds waves interact with\nentropy waves to produce vorticity.
Smooth solutions form a generic\nstable shock with explicitly computable
blowup time\, location\, and\ndirection. Our method establishes the asympt
otic stability of a generic\nshock profile in modulated self-similar varia
bles\, controlling the\ninteraction of three distinct wave families.\n\nTh
is is based on joint work with T. Buckmaster and S. Shkoller.\n
LOCATION:https://researchseminars.org/talk/BODS/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Seonhee Lim (Seoul National University)
DTSTART;VALUE=DATE-TIME:20210614T080000Z
DTEND;VALUE=DATE-TIME:20210614T091500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/18
DESCRIPTION:Title: Br
ownian motion in negative curvature\nby Seonhee Lim (Seoul National Un
iversity) as part of Bremen Online Dynamics Seminar\n\n\nAbstract\nBrownia
n motion in the hyperbolic space $H^n$ is rather\nwell-known with a precis
e formula for the heat kernel\, which is the\nprobability density function
of the Brownian motion. In this talk\, we\nwill talk about the asymptotic
formula for the heat kernel in a\nconnected simply connected negatively c
urved Riemannian manifold X whose\nmetric is lifted from a compact manifol
d M.\n As time goes to infinity\, we show that the heat kernel $p(t\,x\,y)
$ is\nasymptotically $e^{-\\lambda_0} t^{-3/2} C(x\,y)$ where $\\lambda_0$
is the\nbottom of the spectrum of the geometric Laplacian. The proof uses
the\nuniform Harnack inequality on the boundary $\\partial X$ as well as
the\nuniform mixing of the geodesic flow on the quotient manifold M. (This
is\na joint work with François Ledrappier.)\n
LOCATION:https://researchseminars.org/talk/BODS/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wael Bahsoun (Loughborough)
DTSTART;VALUE=DATE-TIME:20210712T133000Z
DTEND;VALUE=DATE-TIME:20210712T144500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/19
DESCRIPTION:Title: Tr
ansfer operators and BV spaces: from classic to anisotropic\nby Wael B
ahsoun (Loughborough) as part of Bremen Online Dynamics Seminar\n\n\nAbstr
act\nSmooth ergodic theory aims to analyse the long-term statistics\nof ch
aotic dynamical systems. There are several analytic and\nprobabilistic too
ls that are used to answer such questions. Each of\nthese approaches has i
ts advantages and its shortcomings\, depending on\nthe system under consid
eration. In this presentation\, I will focus on\ntransfer operator techniq
ues and spectral methods\, which are known to be\nvery powerful when deali
ng with uniformly expanding\, or uniformly\nhyperbolic systems. The first
half of this talk will be rather\nintroductory\, aimed at non-experts\, fo
cusing on ideas behind this\napproach through simple\, yet important examp
les. In the second half of\nthe talk\, I will discuss a recent joint work
with C. Liverani\, whose\nlong-term goal is to provide a good spectral pic
ture for piecewise\nhyperbolic systems with singularities (e.g. billiard m
aps) in any\ndimension. In connection with this goal\, I will also discuss
a recent\njoint work with F. Sélley on coupled map lattices.\n
LOCATION:https://researchseminars.org/talk/BODS/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Folkmar Bornemann (TU München)
DTSTART;VALUE=DATE-TIME:20210726T133000Z
DTEND;VALUE=DATE-TIME:20210726T144500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/20
DESCRIPTION:Title: Fi
nite size effects: random matrices\, quantum chaos\, and Riemann zeros
\nby Folkmar Bornemann (TU München) as part of Bremen Online Dynamics Sem
inar\n\n\nAbstract\nSince the legendary 1972 encounter of H. Montgomery an
d F.\nDyson at tea time in Princeton\, a statistical correspondence of the
\nnon-trivial zeros of the Riemann Zeta function with eigenvalues of\nhigh
-dimensional random matrices has emerged. Surrounded by many deep\nbut not
oriously intractable conjectures\, there is a striking analogy to\nthe ene
rgy levels of a quantum billiard system with chaotic dynamics.\nThe statis
tical accuracy provided by an enormous dataset of more than\none billion z
eros reveals distinctive finite size effects. Using the\nphysical analogy\
, we discuss a precise prediction of these effects that\nhas been obtained
in terms of operator determinants and their\nperturbation series (joint w
ork with P. Forrester and A. Mays\, Melbourne).\n
LOCATION:https://researchseminars.org/talk/BODS/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sergey Zelik (University of Surrey)
DTSTART;VALUE=DATE-TIME:20210913T133000Z
DTEND;VALUE=DATE-TIME:20210913T144500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/21
DESCRIPTION:Title: De
terministic and random attractors for a wave equation with sign changing d
amping\nby Sergey Zelik (University of Surrey) as part of Bremen Onlin
e Dynamics Seminar\n\n\nAbstract\nWe discuss the long-time dynamics gener
ated\nby weakly damped wave equations in bounded 3D domains where\nthe dam
ping coefficient depends explicitly on time and may change sign.\nWe show
that in the case when the non-linearity is super-linear\, the\nconsidered
equation remains dissipative if the weighted mean value of\nthe dissipatio
n rate remains positive and that the conditions of this type\nare not suff
icient in the linear case. Two principally different cases will be\nconsi
dered. In the case when this mean is uniform (which corresponds\nto determ
inistic dissipation rate)\, it will be shown that the considered system\np
ossesses smooth uniform attractors as well as non-autonomous exponential\n
attractors. In the case where the mean is not uniform (which\ncorresponds
to the random dissipation rate\, for instance\, when this dissipation\nrat
e is generated by the Bernoulli process)\, the tempered random\nattractor
will be constructed. In contrast to the usual situation\, this\nrandom att
ractor is expected to have infinite Hausdorff \nand fractal dimensions. T
he simplified model example which demonstrates in\nfinite-dimensionality
of the random attractor will also be presented.\n
LOCATION:https://researchseminars.org/talk/BODS/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jon Aaronson (Tel Aviv University)
DTSTART;VALUE=DATE-TIME:20211129T143000Z
DTEND;VALUE=DATE-TIME:20211129T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/22
DESCRIPTION:Title: Re
newal and ratio mixing properties of "nice" infinite ergodic transformatio
ns\nby Jon Aaronson (Tel Aviv University) as part of Bremen Online Dyn
amics Seminar\n\n\nAbstract\nI'll discuss "ratio mixing" properties\nof
transformations preserving infinite measures ( e.g. as in Hopf's\n1936 bo
ok) and also their "renewal properties"\n(occupation processes to sets of
finite measure). Examples of "nice"\ntransformations considered include ce
rtain null-recurrent Markov\nchains\, - "intermittent" interval maps\, - i
nner functions\, hyperbolic\ngeodesic flows on cyclic covers.\n\nIncludes
joint work with Hitoshi Nakada\, Dalia Terhesiu & Toru Sera.\n
LOCATION:https://researchseminars.org/talk/BODS/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mikhail Hlushchanka (Utrecht University)
DTSTART;VALUE=DATE-TIME:20220110T143000Z
DTEND;VALUE=DATE-TIME:20220110T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/23
DESCRIPTION:by Mikhail Hlushchanka (Utrecht University) as part of Bremen
Online Dynamics Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/BODS/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tushar Das (University of Wisconsin-La Crosse)
DTSTART;VALUE=DATE-TIME:20220131T143000Z
DTEND;VALUE=DATE-TIME:20220131T154500Z
DTSTAMP;VALUE=DATE-TIME:20211128T083757Z
UID:BODS/24
DESCRIPTION:by Tushar Das (University of Wisconsin-La Crosse) as part of B
remen Online Dynamics Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/BODS/24/
END:VEVENT
END:VCALENDAR