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BEGIN:VEVENT
SUMMARY:Eigenstate thermalization hypothesis: correlations and distributio
ns of matrix elements
DTSTART;VALUE=DATE-TIME:20210604T120000Z
DTEND;VALUE=DATE-TIME:20210604T124000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79408@indico.in2p3.fr
DESCRIPTION:Speakers: L. Foini ()\nThe Eigenstate Thermalization Hypothesi
s (ETH) represents a cornerstone in our understanding of the thermalizatio
n mechanism in quantum many body systems.\nIt deals with the matrix elemen
ts of physical observables in the energy eigenbasis and relies on ideas bo
rrowed from quantum chaos and random matrix theory.\nInspired by the recen
t developments in the characterization of chaotic behavior in terms of out
of time order correlations we argue that in order to have non trivial mul
ti-point correlation functions one has to consider correlations between ma
trix elements previously neglected within ETH. \nMoreover we show that gen
eric rotationally invariant random matrix models satisfy a simple relation
: the probability distribution of off-diagonal elements and the one of hal
f the difference between any two diagonal elements coincide.\nIn the spiri
t of ETH we test in different models the hypothesis that the same relation
holds in quantum systems that are non-localized\, when one considers smal
l energy differences. The relation provides a stringent test of ETH beyond
the Gaussian ensemble.\n\nhttps://indico.in2p3.fr/event/20611/contributio
ns/79408/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79408/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum gravity meets statistical physics
DTSTART;VALUE=DATE-TIME:20210602T120000Z
DTEND;VALUE=DATE-TIME:20210602T124000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79421@indico.in2p3.fr
DESCRIPTION:Speakers: J. de Boer ()\nRecent work on quantum gravity has re
vealed deep connections with subjects like quantum information\, statistic
al physics and quantum chaos. In particular\, low-energy effective field t
heories that include gravity turn out to have more access to high-energy d
egrees of freedom than their non-gravitational Wilsonian counterparts. Whi
le precise microscopic high-energy information is inaccessible\, certain s
tatistical high-energy information does manifest itself in an interesting
way at low energies. I will describe some recent work trying to make this
connection more precise\, and explain how it connects to issues like wormh
oles\, averaging over theories and the black hole information paradox.\n\n
https://indico.in2p3.fr/event/20611/contributions/79421/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79421/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Opening
DTSTART;VALUE=DATE-TIME:20210602T114500Z
DTEND;VALUE=DATE-TIME:20210602T120000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-96369@indico.in2p3.fr
DESCRIPTION:https://indico.in2p3.fr/event/20611/contributions/96369/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/96369/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Influence matrix approach to ergodic and non-ergodic quantum dynam
ics
DTSTART;VALUE=DATE-TIME:20210603T124000Z
DTEND;VALUE=DATE-TIME:20210603T132000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79411@indico.in2p3.fr
DESCRIPTION:Speakers: D. Abanin ()\nDynamical properties of a many-body sy
stem are determined by its properties as a quantum bath: the systems that
thermalize act as an efficient bath\, while integrable and many-body local
ized (MBL) systems fail to do so. I will describe a new approach to quantu
m many-body dynamics\, inspired by the notion of the Feynman-Vernon influe
nce functional (IF). I will consider interacting spin systems\, and formul
ate an equation satisfied by their influence functionals. While difficult
in general\, this equation can be solved exactly for a class of many-body
systems – perfect dephasers – which act as Markovian baths on their su
bsystems. More generally\, I will show that\, viewed as a fictitious wave
function in the temporal domain\, influence functional can be described by
tensor-network methods. The efficiency of this approach is based on the b
ehavior of temporal entanglement of the IF\, which surprisingly remains re
latively low in very different physical regimes\, including fast thermaliz
ation\, integrability\, and many-body localization. IF approach offers a n
ew lens on many-body non-equilibrium phenomena\, both in ergodic and non-e
rgodic regimes\, connecting the theory of open quantum systems to quantum
statistical physics.\n\n \n\nBased on: [1] Lerose\, Sonner\, Abanin\, Phys
. Rev. X 11\, 021040 (2021)\; arXiv:2012.00777\; arXiv:2104.07607\n\nhttps
://indico.in2p3.fr/event/20611/contributions/79411/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79411/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Planckian metal and SYK physics at a quantum critical metal with s
pin 1/2 fermions.
DTSTART;VALUE=DATE-TIME:20210603T144000Z
DTEND;VALUE=DATE-TIME:20210603T152000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79413@indico.in2p3.fr
DESCRIPTION:Speakers: O. Parcollet ()\nI will present our recent results o
n a model of itinerant SU(2) electrons with random exchange. This model ho
sts a quantum critical point separating two distinct metallic phases as a
function of doping: a Fermi liquid with a large Fermi surface volume and a
low-doping phase with local moments ordering into a spin-glass. This quan
tum critical point has non-Fermi liquid properties characterized by T-line
ar Planckian behavior\, ω/T scaling and slow spin dynamics of the Sachdev
-Ye-Kitaev (SYK) type.\n\nhttps://indico.in2p3.fr/event/20611/contribution
s/79413/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79413/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Symmetry enriched phases of quantum circuits
DTSTART;VALUE=DATE-TIME:20210603T174000Z
DTEND;VALUE=DATE-TIME:20210603T182000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95678@indico.in2p3.fr
DESCRIPTION:Speakers: E. Altman ()\nQuantum circuits consisting of random
unitary gates and subject to local measurements have been shown to undergo
a phase transition\, tuned by the rate of measurement\, from a state with
volume-law entanglement to an area-law state. I will argue that a much ri
cher phase structure emerges if symmetries are imposed on the circuit. The
classification of phases is governed in this case by an enlarged effectiv
e symmetry\, which combines the physical circuit symmetry with dynamical s
ymmetries associated with the ensemble of quantum trajectories. I'll give
concrete examples for the establishment of steady states\, which would not
have been possible in thermal equilibrium in the presence of the circuit
symmetry alone: (i) Topological states and measurement protected order in
a 1+1 dimensional circuit with Z2 symmetry\; (ii) A critical phase and mea
surement induced Kosterlitz-Thouless transition in a Gaussian Majorana cir
cuit.\n\nhttps://indico.in2p3.fr/event/20611/contributions/95678/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95678/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement and Renyi entropies in chaotic systems: subleading co
rrections
DTSTART;VALUE=DATE-TIME:20210604T174000Z
DTEND;VALUE=DATE-TIME:20210604T182000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95682@indico.in2p3.fr
DESCRIPTION:Speakers: M. Srednicki ()\nThe density matrix of a subsystem o
f a chaotic many-body system in an energy eigenstate can be modeled by a h
ermitian matrix that has been randomly selected from a suitable fixed-trac
e distribution\; at leading order in system volume\, the result is a therm
al density matrix. I will discuss subleading corrections that arise at fin
ite temperature\, but which are usually absent at infinite temperature.\n\
nhttps://indico.in2p3.fr/event/20611/contributions/95682/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95682/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wormholes without averaging
DTSTART;VALUE=DATE-TIME:20210604T170000Z
DTEND;VALUE=DATE-TIME:20210604T174000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95681@indico.in2p3.fr
DESCRIPTION:Speakers: S. Shenker ()\nAfter averaging over fermion coupling
s\, SYK has a collective field description that sometimes has “wormhole
” solutions. We study the fate of these wormholes when the couplings are
fixed. Working mainly in a simple model\, we find that the wormhole saddl
es persist\, but that new saddles also appear elsewhere in the integration
space – “half-wormholes.” The wormhole contributions depend only we
akly on the specific choice of couplings\, while the half-wormhole contrib
utions are strongly sensitive. The half-wormholes are crucial for factoriz
ation of decoupled systems with fixed couplings\, but they vanish after av
eraging\, leaving the non-factorizing wormhole behind. (Joint work with
Phil Saad\, Douglas Stanford and Shunyu Yao.)\n\nhttps://indico.in2p3.fr/
event/20611/contributions/95681/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95681/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum Extremal Surfaces in Isolated Black Holes
DTSTART;VALUE=DATE-TIME:20210604T144000Z
DTEND;VALUE=DATE-TIME:20210604T152000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95680@indico.in2p3.fr
DESCRIPTION:Speakers: N. Engelhardt ()\nTBA\n\nhttps://indico.in2p3.fr/eve
nt/20611/contributions/95680/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95680/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spontaneous Symmetry Breaking in Coupled SYK or Tensor Models
DTSTART;VALUE=DATE-TIME:20210604T140000Z
DTEND;VALUE=DATE-TIME:20210604T144000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95679@indico.in2p3.fr
DESCRIPTION:Speakers: I. Klebanov ()\nhttps://indico.in2p3.fr/event/20611/
contributions/95679/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95679/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simple models and low-temperature quantum chaos
DTSTART;VALUE=DATE-TIME:20210604T124000Z
DTEND;VALUE=DATE-TIME:20210604T132000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79407@indico.in2p3.fr
DESCRIPTION:Speakers: J. Kurchan ()\n(work with S Pappalardi)\nIn the past
few years there has been considerable activity around a set of quantum bo
unds on transport coefficients (viscosity\, conductivity) and on chaos (Ly
apunov exponents)\, relevant at low temperatures. The interest comes from
the fact that AdS/CFT Black-Hole models seem to saturate all of them. I sh
all discuss the simple case of bosonic systems whose lowest energy is a d
egenerate manifold\, and in particular free motion on a curved space\, th
e Hamiltonian being just the Laplace-Beltrami operator. Examples are quant
um hard-sphere liquids and quantum spin liquids. In this context the bound
s are approached and are consequences of the uncertainty principle\, and o
ne understands the mechanisms whereby quantum mechanics enforces them. Fo
r a system to saturate the bound\, it appears as a necessary condition tha
t at each temperature there are some degrees of freedom that are still cla
ssical\, and some are on the verge of being affected by quantum effects.\n
\nhttps://indico.in2p3.fr/event/20611/contributions/79407/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79407/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement island\, miracle operators and the firewall
DTSTART;VALUE=DATE-TIME:20210603T170000Z
DTEND;VALUE=DATE-TIME:20210603T174000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95677@indico.in2p3.fr
DESCRIPTION:Speakers: X. Qi ()\nIn this work\, we obtain some general resu
lts on information retrieval from the black hole interior\, based on the r
ecent progress on quantum extremal surface formula and entanglement island
. We study an AdS black hole coupled to a bath with generic dynamics\, and
ask whether it is possible to retrieve information about a small perturba
tion in the interior from the bath system. We derive a state reconstructio
n formula based on one norm. However\, we show that a contradiction arises
if we apply this result to a special situation when the bath dynamics inc
ludes a unitary operation that carries a particular measurement to a regio
n A and send the result to another region W.Physically\, the contradiction
arises between transferability of classical information during the measur
ement\, and non-transferability of quantum information which determines th
e entanglement island. We propose that the resolution of the contradiction
is to realize that the state reconstruction formula does not apply to the
special situation involving interior-information-retrieving measurements.
This implies that the assumption of smooth replica AdS geometry with boun
dary condition set by the flat space bath has to break down when the parti
cular measurement operator is applied to the bath. Using replica trick\, w
e introduce an explicitly construction of such operator\, which we name as
``miracle operators''. From this construction we see that the smooth repl
ica geometry assumption breaks down because we have to introduce extra rep
lica wormholes connecting with the ``simulated blackholes'' introduced by
the miracle operator. We study the implication of miracle operators in und
erstanding the firewall paradox.\n\nhttps://indico.in2p3.fr/event/20611/co
ntributions/95677/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95677/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Strange metals and the time reparameterization soft mode
DTSTART;VALUE=DATE-TIME:20210603T140000Z
DTEND;VALUE=DATE-TIME:20210603T144000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79412@indico.in2p3.fr
DESCRIPTION:Speakers: S. Sachdev ()\nA strange metal has a resistivity whi
ch is smaller than h/e^2\, with a linear dependence on temperature at low
temperatures. I will describe recent progress in realizing such metals in
theoretical models. Numerical studies of a random t-J model show strange m
etal behavior - I will argue that this is connected to a time reparameteri
zation Schwarzian mode\, similar to that found in the SYK model.This same
mode has been connected in earlier work by others to maximal chaos.\n\nhtt
ps://indico.in2p3.fr/event/20611/contributions/79412/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79412/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ergodic phase in many body quantum chaos
DTSTART;VALUE=DATE-TIME:20210603T120000Z
DTEND;VALUE=DATE-TIME:20210603T124000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79401@indico.in2p3.fr
DESCRIPTION:Speakers: A. Altland ()\nChaotic many body quantum systems can
be in a phase of (many body) localized or extended eigenstates. In recent
years\, the seemingly less enigmatic delocalized phase has become a subje
ct of controversy. It has been suggested that quantum many body eigenstate
s may be Non Ergodic yet Extended (NEE) in Hilbert space\, with exotic mul
tifractal distributions. In this talk I discuss how a blend of concepts de
veloped in different fields --- including matrix integral techniques pione
ered by the French school of field theory\, lessons learned from the SYK m
odel\, and concepts of quantum information applied to random many body sta
tes --- may shed light on the situation.\nOur bottom line will be that (i)
the delocalized quantum states of chaotic systems (subject to long range
interactions) are ergodically distributed over (ii) an energy shell nontri
vially interlaced into Hilbert space. We do not see room for the emergence
of an NEE phase. At the same time (iii)\, the ergodic states of many body
systems show entanglement exceeding that of thermal states\, and of the (
Page) entanglement of pure random states. We will argue that these entangl
ement signatures are sensitive probes into the many body physics of chaoti
c chaos.\n\nhttps://indico.in2p3.fr/event/20611/contributions/79401/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79401/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Non-unitary dynamics via spacetime duality
DTSTART;VALUE=DATE-TIME:20210602T174000Z
DTEND;VALUE=DATE-TIME:20210602T182000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95676@indico.in2p3.fr
DESCRIPTION:Speakers: V. Khemani ()\nThe addition of non-unitary ingredien
ts to many-body quantum dynamics has led to a series of exciting developme
nts in recent years\, including new out-of-equilibrium entanglement phases
and phase transitions enabled by quantum measurements. I will present rec
ent work [1] in which we show that a duality transformation between space
and time on one hand\, and unitarity and non-unitarity on the other\, can
be used to realize non-unitary evolutions whose steady states exhibit a ri
ch variety of behavior in the scaling of their entanglement with subsystem
size — from logarithmic to extensive to fractal. These fractally entang
led states add a qualitatively new entry to the families of many-body quan
tum states that have been studied as energy eigenstates or dynamical stead
y states\, whose entropy almost always displays either area-law\, volume-l
aw or logarithmic scaling. The range of steady-state entanglement scalings
for the non-unitary evolution are closely related to the question of enta
nglement growth in time under different kinds of unitary dynamics\, from l
ocalized to chaotic. This connection is sharpened by an exact mapping to u
nitary evolution with edge decoherence\, in which information is irrevers
ibly “radiated away” from one edge of the system. Finally\, I will di
scuss how these ideas could be experimentally realized with present-day or
near-term quantum technologies\, and how spacetime duality allows us to m
itigate (or eliminate altogether) the overhead from "postselection" of ran
dom measurement outcomes [2].\n\n[1] Matteo Ippoliti\, Tibor Rakovszky\, V
edika Khemani\, arxiv:2103.06873\n[2] Matteo Ippoliti\, Vedika Khemani\, P
RL 126\, 060501 (2021)\n\nhttps://indico.in2p3.fr/event/20611/contribution
s/95676/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95676/
END:VEVENT
BEGIN:VEVENT
SUMMARY:When is the onset of quantum chaos?
DTSTART;VALUE=DATE-TIME:20210602T170000Z
DTEND;VALUE=DATE-TIME:20210602T174000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-95675@indico.in2p3.fr
DESCRIPTION:Speakers: A. Dymarsky ()\nIn a chaotic quantum system matrix e
lements of local operators exhibit statistical properties captured by the
Eigenstate Thermalization Hypothesis. It describes the equilibrium but not
the approach to it. To describe equilibration dynamics correlations betwe
en matrix elements should be taken into account. At late times the correla
tions can be neglected: matrix elements with small energy differences beha
ve as independent random variables\, giving rise to Random Matrix Theory d
escription. This marks the onset of quantum chaos. We show that correspond
ing timescale is parametrically longer than thermalization time\, in a sha
rp distinction with the timescale marking the onset of RMT behavior of the
energy spectrum.\n\nhttps://indico.in2p3.fr/event/20611/contributions/956
75/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/95675/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Delocalization of chaotic eigenmodes
DTSTART;VALUE=DATE-TIME:20210602T144000Z
DTEND;VALUE=DATE-TIME:20210602T152000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79426@indico.in2p3.fr
DESCRIPTION:Speakers: S. Nonnenmacher ()\nIn this talk I will review diffe
rent mathematical results on the\ndelocalization of eigenmodes of the Lapl
acian in closed billiards or compact Riemannian manifolds\, assuming the g
eometry generates a chaotic ray (geodesic) dynamics.\nThe focus will be o
n the high frequency regime\, where semiclassical / microlocal methods can
be applied. In particular I will recall the Quantum Ergodicity Theorem\,
which concerns "almost all" the eigenmodes\, and also give more recent "ab
solute" delocalization results\, especially valid in the case of strongly
chaotic (Anosov) flows.\n\nhttps://indico.in2p3.fr/event/20611/contributio
ns/79426/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79426/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Many-body delocalisation as symmetry breaking
DTSTART;VALUE=DATE-TIME:20210602T124000Z
DTEND;VALUE=DATE-TIME:20210602T132000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79423@indico.in2p3.fr
DESCRIPTION:Speakers: J. Chalker ()\nI will give an overview of recent wor
k on minimal models for quantum chaos and many-body localisation. The mode
ls are Floquet quantum circuits for lattice spin systems\, in which time e
volution is generated by unitary gates that couple neighbouring sites. In
particular\, I will discuss the circumstances in which a version of the so
-called diagonal approximation (originally developed for the semiclassical
limit in low-dimensional chaotic systems) can be applied to these systems
. Within this framework I will show that the many-body delocalisation tran
sition can be seen as a form of symmetry breaking transition\, having many
of the features generally associated with conventional phase transitions
in classical statistical mechanical models. Joint work with Sam Garratt: a
rXiv:2008.01697 and arXiv:2012.11580\n\nhttps://indico.in2p3.fr/event/2061
1/contributions/79423/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79423/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Exact results on dynamics of dual unitary circuits and their pertu
rbations
DTSTART;VALUE=DATE-TIME:20210602T140000Z
DTEND;VALUE=DATE-TIME:20210602T144000Z
DTSTAMP;VALUE=DATE-TIME:20210928T235112Z
UID:indico-contribution-20611-79422@indico.in2p3.fr
DESCRIPTION:Speakers: T. Prosen ()\nI will review the recent results on th
e proof of random matrix spectral form factor and explicit computation of
correlation functions of local observables in the so-called dual-unitary b
rickwork circuits (including integrable\, non-ergodic\, ergodic and chaoti
c cases). Further I will show how these results can be extended to another
quantum-circuit platform\, specifically to unitary interactions round-a-f
ace (IRF). I will argue that correlation functions of these models are gen
erally perturbatively stable with respect to breaking dual-unitarity\, and
describe a simple rigorous result within this framework.\n\nhttps://indic
o.in2p3.fr/event/20611/contributions/79422/
LOCATION:
URL:https://indico.in2p3.fr/event/20611/contributions/79422/
END:VEVENT
END:VCALENDAR