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BEGIN:VEVENT
SUMMARY:Bartek Czech (Tsinghua University)
DTSTART;VALUE=DATE-TIME:20201026T163000Z
DTEND;VALUE=DATE-TIME:20201026T174500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/1
DESCRIPTION:Title: Quer
y complexity and cutoffs in AdS/CFT\nby Bartek Czech (Tsinghua Univers
ity) as part of Purdue HET\n\n\nAbstract\nA quantum state is a map from op
erators to real numbers that are their expectation values. Evaluating this
map always entails using some algorithm\, for example contracting a tenso
r network. I propose a novel way of quantifying the complexity of a quantu
m state in terms of "query complexity": the number of times an efficient a
lgorithm for computing correlation functions in the given state calls on a
certain subroutine. I construct such an algorithm for a general "state at
a cutoff" in 1+1-dimensional field theory. The algorithm scans cutoff-siz
ed intervals for operators whose expectation values will be computed and t
he relevant subroutine is a translation in the space of (cutoff-sized) int
ervals. Query complexity then boils down to an appropriate notion of dista
nce in the space of (cutoff-sized) intervals. A unique distance function i
s consistent with the requisite notion of translations\; therefore the que
ry complexity of a state at a cutoff is unambiguously defined. In holograp
hic theories\, the query complexity evaluates to the integral of the Ricci
scalar on a spatial slice enclosed by the bulk cutoff\, which in pure AdS
3 agrees with the volume proposal but otherwise departs from it.\n
LOCATION:https://researchseminars.org/talk/HET/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Felix Haehl (IAS)
DTSTART;VALUE=DATE-TIME:20201102T173000Z
DTEND;VALUE=DATE-TIME:20201102T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/2
DESCRIPTION:Title: Comm
ents on replica symmetry breaking in spin glasses and gravity\nby Feli
x Haehl (IAS) as part of Purdue HET\n\n\nAbstract\nI will describe some pr
ogress on understanding a model of bosonic spins with disorder averaged co
uplings\, which is quite similar to the SYK model in many regards. What di
stinguishes it from SYK is the appearance of a spin glass phase at low tem
peratures\, where replica symmetry is broken. I will comment on possible i
nterpretations in AdS2 gravity\, where a picture of fragmentation has been
explored previously\, and a lot of progress has been made recently in und
erstanding the relevance of wormhole geometries.\n
LOCATION:https://researchseminars.org/talk/HET/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sridip Pal (IAS\, Princeton)
DTSTART;VALUE=DATE-TIME:20201109T173000Z
DTEND;VALUE=DATE-TIME:20201109T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/3
DESCRIPTION:Title: Univ
ersality in Asymptotic bounds and their saturation in 2D CFT\nby Sridi
p Pal (IAS\, Princeton) as part of Purdue HET\n\n\nAbstract\nWe consider t
he universality of existence and saturation of asymptotic bounds in variou
s quantities in 2D CFT. In particular\, we focus on previously derived upp
er and lower bounds on the number of operators in a window of scaling dime
nsions [Δ−δ\,Δ+δ] at asymptotically large Δ in 2d unitary modular i
nvariant CFTs. These bounds depend on a choice of functions that majorize
and minorize the characteristic function of the interval [Δ−δ\,Δ+δ]
and have Fourier transforms of finite support. The optimization of the bou
nds over this choice turns out to be exactly the Beurling-Selberg extremiz
ation problem\, widely known in analytic number theory. When the width of
the interval is integer\, the bounds are saturated by known partition func
tions with integer-spaced spectra. We further show with numerical assistan
ce that one can see morally similar bounds and saturation in asymptotics o
f various OPE coefficient. The talk will be based on arXiv:2003.14316 [hep
-th] and arXiv: 2011.02482 [hep-th].\n
LOCATION:https://researchseminars.org/talk/HET/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Junyu Liu (Caltech)
DTSTART;VALUE=DATE-TIME:20201130T173000Z
DTEND;VALUE=DATE-TIME:20201130T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/4
DESCRIPTION:Title: Quan
tum computation and "cyberpunkian" quantum field theory\nby Junyu Liu
(Caltech) as part of Purdue HET\n\n\nAbstract\nQuantum field theory is one
of the greatest achievements by human beings in understanding the law of
the universe. Almost all subjects in modern physics\, from condensed-matte
r physics to string theory\, are closely related to the developments of qu
antum field theory. However\, established in the infinite dimensional Hilb
ert spaces\, quantum field theory is very hard to study\, especially when
the theory is strongly coupled. This talk is a summary of quantum opportun
ities for solving quantum field theory theoretically and numerically\, bas
ed on a series of works by the speaker and collaborators. Specifically\, w
e describe a digital quantum simulation algorithm for simulating domain wa
ll scatterings in the 1+1 dimensional quantum field theory\, which could b
e regarded as a toy version of cosmological false vacuum decay in the real
universe\, as an example. We will discuss some potential fundamental limi
tations of classical algorithms\, how quantum computers will help us solve
the problem\, and how good quantum computers are (the quantum-extended Ch
urch-Turing Thesis).\n
LOCATION:https://researchseminars.org/talk/HET/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexander Zhiboedov (CERN)
DTSTART;VALUE=DATE-TIME:20201211T173000Z
DTEND;VALUE=DATE-TIME:20201211T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/5
DESCRIPTION:Title: Conf
ormal collider physics: an update\nby Alexander Zhiboedov (CERN) as pa
rt of Purdue HET\n\n\nAbstract\nI will describe recent progress in underst
anding event shapes in conformal field theories. Familiar from the descrip
tion of hadronic events at colliders\, these observables are computed by m
atrix elements of the so-called light-ray operators. Characterizing the li
ght-ray operators in a nonperturbative setting poses many theoretical chal
lenges. I will describe some of the recently developed tools to perform co
mputations of conformal event shapes and illustrate them using N=4 SYM. Fi
nally\, I will explain how via holography some of the basic properties of
conformal event shapes lead to nontrivial sum rules obeyed by possible UV
completions of general relativity.\n
LOCATION:https://researchseminars.org/talk/HET/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aninda Sinha (Indian Insititute of Science)
DTSTART;VALUE=DATE-TIME:20210125T163000Z
DTEND;VALUE=DATE-TIME:20210125T174500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/6
DESCRIPTION:Title: Enta
nglement in scattering and the S-matrix bootstrap\nby Aninda Sinha (In
dian Insititute of Science) as part of Purdue HET\n\n\nAbstract\nI will ta
lk about how relative entropy\, a concept in quantum information theory to
distinguish two density matrices\, behaves in 2-2 scattering in quantum f
ield theory\, string theory\, chiral perturbation theory and the numerical
S-matrix bootstrap. In the context of massive quantum field theories\, I
will derive high energy bounds on relative entropy as well as study the Re
gge behavior. Then I will turn to the S-matrix bootstrap. I will give a br
oad overview of what this program is about and how to constrain pion scatt
ering with it. Here\, some insight from relative entropy will prove to be
handy to constrain the space of S-matrices. I will discuss some ideas base
d on minimization of total scattering cross-section to constrain pion S-ma
trices further\; curious coincidences such as boundary of allowed S-matric
es being close to the Lovelace-Shapiro model of early string theory\, emer
ging linear Regge trajectories\, as well as reduction in Entanglement powe
r near the standard model point will be discussed.\n
LOCATION:https://researchseminars.org/talk/HET/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Hartman (Cornell University)
DTSTART;VALUE=DATE-TIME:20210208T173000Z
DTEND;VALUE=DATE-TIME:20210208T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/7
DESCRIPTION:Title: Isla
nds in black holes and cosmology\nby Thomas Hartman (Cornell Universit
y) as part of Purdue HET\n\n\nAbstract\nI will summarize recent developmen
ts on the information paradox involving "islands" and replica wormholes\,
and discuss the extent to which these ideas can be applied to cosmology.\n
LOCATION:https://researchseminars.org/talk/HET/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Isaac Kim (Univeristy of Sydney)
DTSTART;VALUE=DATE-TIME:20210222T210000Z
DTEND;VALUE=DATE-TIME:20210222T221500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/8
DESCRIPTION:Title: Entr
opy scaling law and the quantum (and classical) marginal problem\nby I
saac Kim (Univeristy of Sydney) as part of Purdue HET\n\n\nAbstract\nQuant
um (and classical) many-body states that appear in physics often obey an e
ntropy scaling law\, meaning that an entanglement entropy of a subsystem c
an be expressed as a sum of terms that scale linearly with its volume and
area\, plus a correction term that is independent of its size. We conjectu
re that these states have an efficient dual description in terms of a set
of marginal density matrices on bounded regions\, obeying the same entropy
scaling law locally. We prove a restricted version of this conjecture for
translationally invariant systems in two spatial dimensions. Specifically
\, we prove that a translationally invariant marginal obeying three non-li
near constraints -- all of which follow from the entropy scaling law strai
ghtforwardly -- must be consistent with some global state on an infinite l
attice. Moreover\, we derive a closed-form expression for the maximum entr
opy density compatible with those marginals\, deriving a variational upper
bound on the thermodynamic free energy. Our construction's main assumptio
ns are satisfied exactly by solvable models of topological order and appro
ximately by finite-temperature Gibbs states of certain quantum spin Hamilt
onians. To the best of our knowledge\, this is the first nontrivial soluti
on to the quantum marginal problem in a many-body setting that lies strict
ly outside the framework of mean-field theory.\n
LOCATION:https://researchseminars.org/talk/HET/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Horacio Casini (Bariloche Atomic Centre)
DTSTART;VALUE=DATE-TIME:20210301T173000Z
DTEND;VALUE=DATE-TIME:20210301T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/9
DESCRIPTION:Title: Entr
opic order parameters for symmetries in QFT\nby Horacio Casini (Barilo
che Atomic Centre) as part of Purdue HET\n\n\nAbstract\nIn QFT there is an
algebra of operators attached to any spacetime region. Simple degradation
s of the most harmonious possible relation between algebras and regions ar
e shown to encode generalized symmetries. Nets of algebras with these symm
etries allow for a non uniqueness of the algebras that can be assigned to
a given region. This non uniqueness suggests a simple geometrical order pa
rameter in terms of a relative entropy. These satisfy a ''certainty relati
on'' connecting the statistics of the order and disorder parameters for co
mplementary regions. We describe how the lore about phases of theories wit
h generalized symmetries is seen in this new picture.\n
LOCATION:https://researchseminars.org/talk/HET/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stefan Hollands (Leipzig University)
DTSTART;VALUE=DATE-TIME:20210217T163000Z
DTEND;VALUE=DATE-TIME:20210217T174500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/10
DESCRIPTION:Title: (In
)determinism Inside Black Holes\nby Stefan Hollands (Leipzig Universit
y) as part of Purdue HET\n\n\nAbstract\nIn classical General Relativity\,
the values of fields on spacetime are\nuniquely determined by their initia
l values within its 'domain of\ndependence'. However\, it may occur that t
he\nspacetime under consideration extends beyond this domain\, and\nfields
\, therefore\, are not entirely determined by their initial data. \nSuch
a naive\nfailure of determinism occurs inside all physically relevant blac
k holes.\n\nThe boundary of the region determined by the initial data is\n
called the 'Cauchy horizon'. Penrose has proposed ('strong cosmic \ncenso
rship conjecture')\nthat the Cauchy horizon is actually unstable in the se
nse that the \nslightest perturbation caused\nby remnant fields convert i
t to a final singularity. Whether or not \nthis is the case --\nand thus
whether there is a real problem with determinism -- has been \ndebated re
cently.\n\nIn this talk I ask whether quantum effects will come to the res
cue of \nstrong cosmic censorship.\n
LOCATION:https://researchseminars.org/talk/HET/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandre Belin (CERN)
DTSTART;VALUE=DATE-TIME:20210315T163000Z
DTEND;VALUE=DATE-TIME:20210315T174500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/11
DESCRIPTION:Title: The
OPE Randomness Hypothesis and Euclidean Wormholes\nby Alexandre Belin
(CERN) as part of Purdue HET\n\n\nAbstract\nRecent developments in hologr
aphy indicate that the semi-classical Euclidean path-integral of Einstein
gravity is much more powerful than previously anticipated. It is capable o
f reproducing a unitary Page curve for black hole evaporation\, and can ev
en capture some features of the discrete nature of black hole microstates.
Wormhole geometries play a key role in this context. I will propose a mec
hanism to explain this in the CFT: the OPE Randomness Hypothesis. This ans
atz is a generalization of the Eigenstate Thermalization Hypothesis which
applies to chaotic CFTs\, and treats OPE coefficients of heavy operators a
s random variables with a given probability distribution. I will present t
wo applications of this framework: First\, it resolves a factorization puz
zle in AdS_3/CFT_2 due to the genus-2 wormhole\, as raised by Maoz and Mal
dacena. Second\, it provides an argument against global symmetries in quan
tum gravity.\n
LOCATION:https://researchseminars.org/talk/HET/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicholas LaRacuente (University of Chicago)
DTSTART;VALUE=DATE-TIME:20210118T173000Z
DTEND;VALUE=DATE-TIME:20210118T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/12
DESCRIPTION:Title: Mul
tivariate Trace Inequalities\, p-Fidelity\, and Universal Recovery Beyond
Tracial von Neumann Algebras\nby Nicholas LaRacuente (University of Ch
icago) as part of Purdue HET\n\n\nAbstract\nTrace inequalities are powerfu
l in quantum information theory\, often replacing classical functional cal
culus in noncommutative settings. The physics of quantum field theory and
holography\, however\, motivate entropy inequalities in von Neumann algebr
as that lack a useful notion of a trace. The Haagerup and Kosaki Lp spaces
enable re-expressing trace inequalities in non-tracial von Neumann algebr
as. In particular\, we show this for the generalized Araki-Lieb-Thirring a
nd Golden-Thompson inequalities from (Sutter\, Berta & Tomamichel 2017). T
hen\, using the Haagerup approximation method\, we prove a general von Neu
mann algebra version of the recovery map tightening of the data processing
inequality for relative entropy. We also generalize via subharmonicity of
a logarithmic p-fidelity of recovery. Furthermore\, we prove that non-dec
rease of relative entropy is equivalent to existence of an L1-isometry imp
lementing the channel on both input states.\n
LOCATION:https://researchseminars.org/talk/HET/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adam Levine (IAS Princeton)
DTSTART;VALUE=DATE-TIME:20210308T173000Z
DTEND;VALUE=DATE-TIME:20210308T184500Z
DTSTAMP;VALUE=DATE-TIME:20210419T092204Z
UID:HET/13
DESCRIPTION:Title: Pro
bing strings with quantum extremal surfaces\nby Adam Levine (IAS Princ
eton) as part of Purdue HET\n\n\nAbstract\nWe drop a particle or string in
to vacuum AdS and ask whether the excitation is in the entanglement wedge
for a region composed of a Rindler wedge together with a small interval. W
e compute the quantum fidelity between the state with a particle and the s
tate without a particle\, which is a direct measure of whether the particl
e is reconstructable from this region. We find that in a gravitational the
ory and for a purely chiral probe particle\, the distinction of whether th
e excitation is in the entanglement wedge or not is sharp\, corresponding
precisely with when the excitation passes across the quantum extremal surf
ace. For a theory with a non-zero string length\, we find that this distin
ction between when the particle is inside or outside the entanglement wedg
e becomes fuzzy and depends on the smearing scale of the particle creation
operator. We comment on an interpretation of this phenomenon in terms of
string spreading. Based upon forthcoming work with Ven Chandrasekaran and
Tom Faulkner.\n
LOCATION:https://researchseminars.org/talk/HET/13/
END:VEVENT
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