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BEGIN:VEVENT
SUMMARY:Bartek Czech (Tsinghua University)
DTSTART:20201026T163000Z
DTEND:20201026T174500Z
DTSTAMP:20260404T094648Z
UID:HET/1
DESCRIPTION:Title: Query complexity and cutoffs in AdS/CFT\nby Bartek Czech (Tsinghua
University) as part of Purdue HET\n\n\nAbstract\nA quantum state is a map
from operators to real numbers that are their expectation values. Evaluati
ng this map always entails using some algorithm\, for example contracting
a tensor network. I propose a novel way of quantifying the complexity of a
quantum state in terms of "query complexity": the number of times an effi
cient algorithm for computing correlation functions in the given state cal
ls on a certain subroutine. I construct such an algorithm for a general "s
tate at a cutoff" in 1+1-dimensional field theory. The algorithm scans cut
off-sized intervals for operators whose expectation values will be compute
d and the relevant subroutine is a translation in the space of (cutoff-siz
ed) intervals. Query complexity then boils down to an appropriate notion o
f distance in the space of (cutoff-sized) intervals. A unique distance fun
ction is consistent with the requisite notion of translations\; therefore
the query complexity of a state at a cutoff is unambiguously defined. In h
olographic theories\, the query complexity evaluates to the integral of th
e Ricci scalar on a spatial slice enclosed by the bulk cutoff\, which in p
ure AdS3 agrees with the volume proposal but otherwise departs from it.\n
LOCATION:https://stable.researchseminars.org/talk/HET/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Felix Haehl (IAS)
DTSTART:20201102T173000Z
DTEND:20201102T184500Z
DTSTAMP:20260404T094648Z
UID:HET/2
DESCRIPTION:Title: Comments on replica symmetry breaking in spin glasses and gravity\n
by Felix Haehl (IAS) as part of Purdue HET\n\n\nAbstract\nI will describe
some progress on understanding a model of bosonic spins with disorder aver
aged couplings\, which is quite similar to the SYK model in many regards.
What distinguishes it from SYK is the appearance of a spin glass phase at
low temperatures\, where replica symmetry is broken. I will comment on pos
sible interpretations in AdS2 gravity\, where a picture of fragmentation h
as been explored previously\, and a lot of progress has been made recently
in understanding the relevance of wormhole geometries.\n
LOCATION:https://stable.researchseminars.org/talk/HET/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sridip Pal (IAS\, Princeton)
DTSTART:20201109T173000Z
DTEND:20201109T184500Z
DTSTAMP:20260404T094648Z
UID:HET/3
DESCRIPTION:Title: Universality in Asymptotic bounds and their saturation in 2D CFT\nb
y Sridip Pal (IAS\, Princeton) as part of Purdue HET\n\n\nAbstract\nWe con
sider the universality of existence and saturation of asymptotic bounds in
various quantities in 2D CFT. In particular\, we focus on previously deri
ved upper and lower bounds on the number of operators in a window of scali
ng dimensions [Δ−δ\,Δ+δ] at asymptotically large Δ in 2d unitary mo
dular invariant CFTs. These bounds depend on a choice of functions that ma
jorize and minorize the characteristic function of the interval [Δ−δ\,
Δ+δ] and have Fourier transforms of finite support. The optimization of
the bounds over this choice turns out to be exactly the Beurling-Selberg e
xtremization problem\, widely known in analytic number theory. When the wi
dth of the interval is integer\, the bounds are saturated by known partiti
on functions with integer-spaced spectra. We further show with numerical a
ssistance that one can see morally similar bounds and saturation in asympt
otics of various OPE coefficient. The talk will be based on arXiv:2003.143
16 [hep-th] and arXiv: 2011.02482 [hep-th].\n
LOCATION:https://stable.researchseminars.org/talk/HET/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Junyu Liu (Caltech)
DTSTART:20201130T173000Z
DTEND:20201130T184500Z
DTSTAMP:20260404T094648Z
UID:HET/4
DESCRIPTION:Title: Quantum computation and "cyberpunkian" quantum field theory\nby Jun
yu 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 condense
d-matter physics to string theory\, are closely related to the development
s of quantum field theory. However\, established in the infinite dimension
al Hilbert spaces\, quantum field theory is very hard to study\, especiall
y when the theory is strongly coupled. This talk is a summary of quantum o
pportunities for solving quantum field theory theoretically and numericall
y\, based on a series of works by the speaker and collaborators. Specifica
lly\, we describe a digital quantum simulation algorithm for simulating do
main wall scatterings in the 1+1 dimensional quantum field theory\, which
could be regarded as a toy version of cosmological false vacuum decay in t
he real universe\, as an example. We will discuss some potential fundament
al limitations of classical algorithms\, how quantum computers will help u
s solve the problem\, and how good quantum computers are (the quantum-exte
nded Church-Turing Thesis).\n
LOCATION:https://stable.researchseminars.org/talk/HET/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexander Zhiboedov (CERN)
DTSTART:20201211T173000Z
DTEND:20201211T184500Z
DTSTAMP:20260404T094648Z
UID:HET/5
DESCRIPTION:Title: Conformal collider physics: an update\nby Alexander Zhiboedov (CERN
) as part of Purdue HET\n\n\nAbstract\nI will describe recent progress in
understanding event shapes in conformal field theories. Familiar from the
description of hadronic events at colliders\, these observables are comput
ed by matrix elements of the so-called light-ray operators. Characterizing
the light-ray operators in a nonperturbative setting poses many theoretic
al challenges. I will describe some of the recently developed tools to per
form computations of conformal event shapes and illustrate them using N=4
SYM. Finally\, I will explain how via holography some of the basic propert
ies of conformal event shapes lead to nontrivial sum rules obeyed by possi
ble UV completions of general relativity.\n
LOCATION:https://stable.researchseminars.org/talk/HET/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aninda Sinha (Indian Insititute of Science)
DTSTART:20210125T163000Z
DTEND:20210125T174500Z
DTSTAMP:20260404T094648Z
UID:HET/6
DESCRIPTION:Title: Entanglement in scattering and the S-matrix bootstrap\nby Aninda Si
nha (Indian Insititute of Science) as part of Purdue HET\n\n\nAbstract\nI
will talk about how relative entropy\, a concept in quantum information th
eory to distinguish two density matrices\, behaves in 2-2 scattering in qu
antum field theory\, string theory\, chiral perturbation theory and the nu
merical S-matrix bootstrap. In the context of massive quantum field theori
es\, I will derive high energy bounds on relative entropy as well as study
the Regge behavior. Then I will turn to the S-matrix bootstrap. I will gi
ve a broad overview of what this program is about and how to constrain pio
n scattering with it. Here\, some insight from relative entropy will prove
to be handy to constrain the space of S-matrices. I will discuss some ide
as based on minimization of total scattering cross-section to constrain pi
on S-matrices further\; curious coincidences such as boundary of allowed S
-matrices being close to the Lovelace-Shapiro model of early string theory
\, emerging linear Regge trajectories\, as well as reduction in Entangleme
nt power near the standard model point will be discussed.\n
LOCATION:https://stable.researchseminars.org/talk/HET/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Hartman (Cornell University)
DTSTART:20210208T173000Z
DTEND:20210208T184500Z
DTSTAMP:20260404T094648Z
UID:HET/7
DESCRIPTION:Title: Islands in black holes and cosmology\nby Thomas Hartman (Cornell Un
iversity) as part of Purdue HET\n\n\nAbstract\nI will summarize recent dev
elopments on the information paradox involving "islands" and replica wormh
oles\, and discuss the extent to which these ideas can be applied to cosmo
logy.\n
LOCATION:https://stable.researchseminars.org/talk/HET/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Isaac Kim (Univeristy of Sydney)
DTSTART:20210222T210000Z
DTEND:20210222T221500Z
DTSTAMP:20260404T094648Z
UID:HET/8
DESCRIPTION:Title: Entropy scaling law and the quantum (and classical) marginal problem\nby Isaac Kim (Univeristy of Sydney) as part of Purdue HET\n\n\nAbstract
\nQuantum (and classical) many-body states that appear in physics often ob
ey an entropy scaling law\, meaning that an entanglement entropy of a subs
ystem can be expressed as a sum of terms that scale linearly with its volu
me and area\, plus a correction term that is independent of its size. We c
onjecture 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 conject
ure for translationally invariant systems in two spatial dimensions. Speci
fically\, we prove that a translationally invariant marginal obeying three
non-linear constraints -- all of which follow from the entropy scaling la
w straightforwardly -- must be consistent with some global state on an inf
inite lattice. Moreover\, we derive a closed-form expression for the maxim
um entropy density compatible with those marginals\, deriving a variationa
l upper bound on the thermodynamic free energy. Our construction's main as
sumptions are satisfied exactly by solvable models of topological order an
d approximately by finite-temperature Gibbs states of certain quantum spin
Hamiltonians. To the best of our knowledge\, this is the first nontrivial
solution to the quantum marginal problem in a many-body setting that lies
strictly outside the framework of mean-field theory.\n
LOCATION:https://stable.researchseminars.org/talk/HET/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Horacio Casini (Bariloche Atomic Centre)
DTSTART:20210301T173000Z
DTEND:20210301T184500Z
DTSTAMP:20260404T094648Z
UID:HET/9
DESCRIPTION:Title: Entropic order parameters for symmetries in QFT\nby Horacio Casini
(Bariloche Atomic Centre) as part of Purdue HET\n\n\nAbstract\nIn QFT ther
e is an algebra of operators attached to any spacetime region. Simple degr
adations of the most harmonious possible relation between algebras and reg
ions are shown to encode generalized symmetries. Nets of algebras with the
se symmetries allow for a non uniqueness of the algebras that can be assig
ned to a given region. This non uniqueness suggests a simple geometrical o
rder parameter in terms of a relative entropy. These satisfy a ''certainty
relation'' connecting the statistics of the order and disorder parameters
for complementary regions. We describe how the lore about phases of theor
ies with generalized symmetries is seen in this new picture.\n
LOCATION:https://stable.researchseminars.org/talk/HET/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stefan Hollands (Leipzig University)
DTSTART:20210217T163000Z
DTEND:20210217T174500Z
DTSTAMP:20260404T094648Z
UID:HET/10
DESCRIPTION:Title: (In)determinism Inside Black Holes\nby Stefan Hollands (Leipzig Un
iversity) as part of Purdue HET\n\n\nAbstract\nIn classical General Relati
vity\, the values of fields on spacetime are\nuniquely determined by their
initial values within its 'domain of\ndependence'. However\, it may occur
that the\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 releva
nt black holes.\n\nThe boundary of the region determined by the initial da
ta is\ncalled the 'Cauchy horizon'. Penrose has proposed ('strong cosmic
\ncensorship conjecture')\nthat the Cauchy horizon is actually unstable in
the sense that the \nslightest perturbation caused\nby remnant fields co
nvert it to a final singularity. Whether or not \nthis is the case --\nan
d thus whether there is a real problem with determinism -- has been \ndeb
ated recently.\n\nIn this talk I ask whether quantum effects will come to
the rescue of \nstrong cosmic censorship.\n
LOCATION:https://stable.researchseminars.org/talk/HET/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandre Belin (CERN)
DTSTART:20210315T163000Z
DTEND:20210315T174500Z
DTSTAMP:20260404T094648Z
UID:HET/11
DESCRIPTION:Title: The OPE Randomness Hypothesis and Euclidean Wormholes\nby Alexandr
e Belin (CERN) as part of Purdue HET\n\n\nAbstract\nRecent developments in
holography indicate that the semi-classical Euclidean path-integral of Ei
nstein gravity is much more powerful than previously anticipated. It is ca
pable of reproducing a unitary Page curve for black hole evaporation\, and
can even capture some features of the discrete nature of black hole micro
states. Wormhole geometries play a key role in this context. I will propos
e a mechanism to explain this in the CFT: the OPE Randomness Hypothesis. T
his ansatz is a generalization of the Eigenstate Thermalization Hypothesis
which applies to chaotic CFTs\, and treats OPE coefficients of heavy oper
ators as random variables with a given probability distribution. I will pr
esent two applications of this framework: First\, it resolves a factorizat
ion puzzle in AdS_3/CFT_2 due to the genus-2 wormhole\, as raised by Maoz
and Maldacena. Second\, it provides an argument against global symmetries
in quantum gravity.\n
LOCATION:https://stable.researchseminars.org/talk/HET/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicholas LaRacuente (University of Chicago)
DTSTART:20210118T173000Z
DTEND:20210118T184500Z
DTSTAMP:20260404T094648Z
UID:HET/12
DESCRIPTION:Title: Multivariate Trace Inequalities\, p-Fidelity\, and Universal Recovery
Beyond Tracial von Neumann Algebras\nby Nicholas LaRacuente (Universit
y of Chicago) as part of Purdue HET\n\n\nAbstract\nTrace inequalities are
powerful in quantum information theory\, often replacing classical functio
nal calculus in noncommutative settings. The physics of quantum field theo
ry and holography\, however\, motivate entropy inequalities in von Neumann
algebras that lack a useful notion of a trace. The Haagerup and Kosaki Lp
spaces enable re-expressing trace inequalities in non-tracial von Neumann
algebras. In particular\, we show this for the generalized Araki-Lieb-Thi
rring and Golden-Thompson inequalities from (Sutter\, Berta & Tomamichel 2
017). Then\, using the Haagerup approximation method\, we prove a general
von Neumann algebra version of the recovery map tightening of the data pro
cessing inequality for relative entropy. We also generalize via subharmoni
city of a logarithmic p-fidelity of recovery. Furthermore\, we prove that
non-decrease of relative entropy is equivalent to existence of an L1-isome
try implementing the channel on both input states.\n
LOCATION:https://stable.researchseminars.org/talk/HET/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adam Levine (IAS Princeton)
DTSTART:20210308T173000Z
DTEND:20210308T184500Z
DTSTAMP:20260404T094648Z
UID:HET/13
DESCRIPTION:Title: Probing strings with quantum extremal surfaces\nby Adam Levine (IA
S Princeton) as part of Purdue HET\n\n\nAbstract\nWe drop a particle or st
ring into vacuum AdS and ask whether the excitation is in the entanglement
wedge for a region composed of a Rindler wedge together with a small inte
rval. We compute the quantum fidelity between the state with a particle an
d the state without a particle\, which is a direct measure of whether the
particle is reconstructable from this region. We find that in a gravitatio
nal theory and for a purely chiral probe particle\, the distinction of whe
ther the excitation is in the entanglement wedge or not is sharp\, corresp
onding precisely with when the excitation passes across the quantum extrem
al surface. For a theory with a non-zero string length\, we find that this
distinction between when the particle is inside or outside the entangleme
nt wedge becomes fuzzy and depends on the smearing scale of the particle c
reation operator. We comment on an interpretation of this phenomenon in te
rms of string spreading. Based upon forthcoming work with Ven Chandrasekar
an and Tom Faulkner.\n
LOCATION:https://stable.researchseminars.org/talk/HET/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shinsei Ryu (Princeton University)
DTSTART:20211012T193000Z
DTEND:20211012T204500Z
DTSTAMP:20260404T094648Z
UID:HET/14
DESCRIPTION:Title: Multipartitioning topological phases and quantum entangle\nby Shin
sei Ryu (Princeton University) as part of Purdue HET\n\n\nAbstract\nWe dis
cuss multipartitions of the gapped ground states of (2+1)-dimensional topo
logical liquids into three (or more) spatial regions that are adjacent to
each other and meet at points. By considering the reduced density matrix o
btained by tracing over a subset of the regions\, we compute various corre
lation measures\, such as entanglement negativity\, reflected entropy\,
and associated spectra. We utilize the bulk-boundary correspondence to ach
ieve such multipartitions and construct the reduced density matrix near th
e entangling boundaries. We find the fingerprints of topological liquid in
these quantities\, such as (universal pieces in) the scaling of the entan
glement negativity\, and a non-trivial distribution of the spectrum of the
partially transposed density matrix. For reflected entropy\, we test the
recent claim that states the difference between reflected entropy and mutu
al information is given\, once short range correlations are properly remov
ed\, by (|c|/3) ln 2 where c is the chiral central charge of the topologic
al liquid.\n
LOCATION:https://stable.researchseminars.org/talk/HET/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Raghu Mahajan (Stanford University)
DTSTART:20210921T193000Z
DTEND:20210921T204500Z
DTSTAMP:20260404T094648Z
UID:HET/15
DESCRIPTION:Title: Sphere and disk partition functions in Liouville and in matrix integra
ls\nby Raghu Mahajan (Stanford University) as part of Purdue HET\n\n\n
Abstract\nWe compute the sphere and disk partition functions in semiclassi
cal Liouville string theory (without any vertex operator insertions) and a
nalogous quantities in double-scaled matrix integrals. The quantity sphere
/ disk^2 is independent of the string coupling constant and we find a pre
cise numerical match between the Liouville answer and the matrix integral
answer.\n\nThe main idea in the string theory computation is that the Liou
ville path integral has a noncompact family of saddle points that are rela
ted by the PSL(2\,C) and PSL(2\,R) conformal symmetries on the sphere and
the disk\, respectively. Faddeev-Popov gauge fixing then allows us to over
come the usual difficulty associated with residual gauge symmetries on the
sphere and the disk. \n\n(Based on joint work with Douglas Stanford and C
ynthia Yan.)\n
LOCATION:https://stable.researchseminars.org/talk/HET/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Kolchmeyer (Harvard University)
DTSTART:20211005T193000Z
DTEND:20211005T204500Z
DTSTAMP:20260404T094648Z
UID:HET/16
DESCRIPTION:Title: The Eigenstate Thermalization Hypothesis in JT gravity with matter
\nby David Kolchmeyer (Harvard University) as part of Purdue HET\n\n\nAbst
ract\nI will discuss ongoing efforts to find a two-matrix model dual to JT
gravity coupled to a free massive scalar field that admits an interpretat
ion in terms of the Eigenstate Thermalization Hypothesis (ETH). The two He
rmitian matrices\, H and O\, represent the boundary Hamiltonian and the bo
undary operator dual to the bulk scalar field. The gravitational path inte
gral implies that the matrix elements of O in the H eigenbasis obey a cert
ain constraint. We use this constraint to make a conjecture about the form
of the matrix model potential. This conjecture can be tested using a q-de
formation of JT gravity with matter. This talk is based on work in progres
s with Daniel Jafferis\, Baur Mukhametzhanov\, and Julian Sonner.\n
LOCATION:https://stable.researchseminars.org/talk/HET/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Kapec (IAS Princeton)
DTSTART:20211019T193000Z
DTEND:20211019T204500Z
DTSTAMP:20260404T094648Z
UID:HET/17
DESCRIPTION:Title: Shadows and Soft Exchange in Celestial CFT\nby Daniel Kapec (IAS P
rinceton) as part of Purdue HET\n\n\nAbstract\nI will discuss exponentiate
d soft exchange in (d+2)-dimensional gauge and gravitational theories usin
g the celestial CFT formalism. These models exhibit spontaneously broken a
symptotic symmetries generated by gauge transformations with non-compact s
upport\, and the effective dynamics of the associated Goldstone “edge”
mode is expected to be d-dimensional. The introduction of an infrared reg
ulator also explicitly breaks these symmetries so the edge mode in the reg
ulated theory is really a d-dimensional pseudo-Goldstone boson. Symmetry c
onsiderations determine the leading terms in the effective action\, whose
coefficients are controlled by the infrared cutoff. Computations in this m
odel reproduce the abelian infrared divergences in d=2\, and capture the r
e-summed (infrared finite) soft exchange in higher dimensions. The model a
lso reproduces the leading soft theorems in gauge and gravitational theori
es in all dimensions. Interestingly\, we find that it is the shadow transf
orm of the Goldstone mode that has local d-dimensional dynamics: the effec
tive action expressed in terms of the Goldstone mode is non-local for d>2.
The analysis demonstrates that symmetry principles suffice to calculate s
oft exchange in gauge theory and gravity.\n
LOCATION:https://stable.researchseminars.org/talk/HET/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Sully (University of British Colombia)
DTSTART:20211102T193000Z
DTEND:20211102T204500Z
DTSTAMP:20260404T094648Z
UID:HET/18
DESCRIPTION:Title: Inner Turmoil: Complexity\, Chaos\, and the Black Hole Interior\nb
y James Sully (University of British Colombia) as part of Purdue HET\n\n\n
Abstract\nI will describe a precise and computationally tractable notion o
f operator complexity in quantum theories. In holographic theories\, this
refined version of K-complexity exhibits exponential growth for a scrambli
ng time\, followed by linear growth until saturation at a time exponential
in the entropy—a behavior that is characteristic of chaos. I will expla
in how the linear growth regime implies a universal random matrix descript
ion of the operator dynamics after scrambling. Our main tool for establish
ing this connection is a “complexity renormalization group” where we i
ntegrate out large K-complexities. Finally\, I will discuss a connection b
etween the universal random matrix theory dynamics of operator growth afte
r scrambling and the geometry of smooth black hole interiors.\n
LOCATION:https://stable.researchseminars.org/talk/HET/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jennifer Lin (University of Oxford)
DTSTART:20211026T153000Z
DTEND:20211026T164500Z
DTSTAMP:20260404T094648Z
UID:HET/19
DESCRIPTION:Title: A new look at the gravitational entropy formula\nby Jennifer Lin (
University of Oxford) as part of Purdue HET\n\n\nAbstract\nThe Ryu-Takayan
agi formula and its generalizations have led to a surprising amount of pro
gress in our understanding of quantum gravity in the last fifteen years\,
culminating in the recent derivation of the Page curve in toy models of ev
aporating black holes. However\, we still don’t understand why these fo
rmulas are true from a canonical point of view. In this talk\, I will atte
mpt to make progress on this problem by developing an analogy between grav
itational entropy formulas in low-dimensional examples of holography and s
imilar-looking formulas that have appeared in the study of entanglement en
tropy in emergent gauge theories. This talk will be based on 1807.06575\,
2107.11872\, and 2107.12634.\n
LOCATION:https://stable.researchseminars.org/talk/HET/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brian Swingle
DTSTART:20210928T193000Z
DTEND:20210928T204500Z
DTSTAMP:20260404T094648Z
UID:HET/20
DESCRIPTION:Title: Hydrodynamics and the Spectral Form Factor\nby Brian Swingle as pa
rt of Purdue HET\n\n\nAbstract\nEnsembles of quantum chaotic systems are e
xpected to exhibit random matrix universality in their energy spectrum. Th
e presence of this universality can be diagnosed by looking for a linear i
n time 'ramp' in the spectral form factor\, but for realistic systems this
feature is typically only visible after a sufficiently long time. It is i
mportant to understand the emergence of this universality and how it conne
cts to the larger body of phenomena associated with quantum chaos. This ta
lk will present a hydrodynamic theory of the spectral form factor in syste
ms with slow modes. The formalism predicts the linear ramp at sufficiently
late time and gives a quantitative framework for computing the approach t
o ramp.\n
LOCATION:https://stable.researchseminars.org/talk/HET/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ro Jefferson (NORDITA)
DTSTART:20211109T203000Z
DTEND:20211109T214500Z
DTSTAMP:20260404T094648Z
UID:HET/21
DESCRIPTION:Title: The edge of chaos: quantum field theory and deep neural networks\n
by Ro Jefferson (NORDITA) as part of Purdue HET\n\n\nAbstract\nThe nascent
NN-QFT correspondence offers an interesting\, physics-based approach towa
rds a theoretical foundation for deep neural networks. In this talk\, I wi
ll discuss recent work in which we explicitly construct the QFT correspond
ing to a general class of networks encompassing both recurrent and feedfor
ward architectures. The point at which the network exhibits critical behav
iour can then be obtained by examining the largest Lyapunov exponent in a
proper mean field theory treatment. However\, this and previous results in
the literature hold only at infinite width\, while empirical evidence sug
gests that the correlation length receives significant corrections in real
-world (finite width) networks. Hence\, going beyond the mean field regime
\, we develop a perturbative approach formally analogous to that in the O(
N) vector model\, in which the weight variance plays the role of the 't Ho
oft coupling. In particular\, we compute both the O(1) corrections quantif
ying fluctuations from typicality in the ensemble of networks\, and the su
bleading O(depth/width) corrections due to finite-width effects. I will in
troduce the use of Feynman diagrams in this context for linear models\, an
d discuss the generalization to nonlinear models if time permits.\n
LOCATION:https://stable.researchseminars.org/talk/HET/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pratik Rath (UCSB)
DTSTART:20211116T203000Z
DTEND:20211116T214500Z
DTSTAMP:20260404T094648Z
UID:HET/22
DESCRIPTION:Title: The Page curve for Reflected Entropy\nby Pratik Rath (UCSB) as par
t of Purdue HET\n\n\nAbstract\nReflected Entropy is a bipartite correlatio
n measure with a simple geometric holographic dual\, the minimal entanglem
ent wedge cross section. This duality further motivates the idea that spac
etime emerges from entanglement and illustrates the richness of the multip
artite entanglement structure of holographic systems. A particularly inter
esting feature that we focus on in this talk is the phase transition betwe
en a connected and disconnected entanglement wedge where the reflected ent
ropy jumps discontinuously. We explain how this phase transition is resolv
ed in tensor networks and a model of JT gravity which motivate a general a
nsatz for the mechanism of the phase transition in AdS/CFT. We also demons
trate how the reflected entropy calculation motivates a procedure for buil
ding up geometry using tensor networks.\n
LOCATION:https://stable.researchseminars.org/talk/HET/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michal P. Heller (Ghent University)
DTSTART:20220125T203000Z
DTEND:20220125T213000Z
DTSTAMP:20260404T094648Z
UID:HET/23
DESCRIPTION:Title: Entanglement of Purification (and Reflected Entropy) in Conformal Fiel
d Theory\nby Michal P. Heller (Ghent University) as part of Purdue HET
\n\n\nAbstract\nQuantifying entanglement properties of mixed states in qua
ntum field theory via entanglement of purification and reflected entropy i
s a new and challenging subject. I will discuss universal CFT results on e
ntanglement of purification (and also on reflected entropy) in the paradig
matic example of two spherical subregions far away from each other in the
vacuum of a conformal field theory. Based on 2009.11881\, 2102.00013 and w
ork in progress.\n
LOCATION:https://stable.researchseminars.org/talk/HET/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Edgar Shaghoulian (University of Pennsylvania)
DTSTART:20220301T203000Z
DTEND:20220301T213000Z
DTSTAMP:20260404T094648Z
UID:HET/25
DESCRIPTION:Title: The central dogma and entanglement in de Sitter space\nby Edgar Sh
aghoulian (University of Pennsylvania) as part of Purdue HET\n\n\nAbstract
\nThe central dogma of black hole physics – which says that from the out
side a black hole can be described in terms of a quantum system with exp(A
rea/4G) states evolving unitarily – has recently been supported by compu
tations indicating that the interior of the black hole is encoded in the H
awking radiation of the exterior. In this paper\, we probe whether such a
dogma for cosmological horizons has any support from similar computations.
The fact that the de Sitter bifurcation surface is a minimax surface (ins
tead of a maximin surface) causes problems with this interpretation when t
rying to import calculations analogous to the AdS case. This suggests anch
oring extremal surfaces to the horizon itself\, where we formulate a two-s
ided extremization prescription and find answers consistent with general e
xpectations for a quantum theory of de Sitter space: vanishing total entro
py\, an entropy of A/4G when restricting to a single static patch\, an ent
ropy of a subregion of the horizon which grows with the region size and th
reatens the central dogma until an island-like transition at half the hori
zon size when the entanglement wedge becomes the entire static patch inter
ior\, and a de Sitter version of the Hartman-Maldacena transition.\n
LOCATION:https://stable.researchseminars.org/talk/HET/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:John McGreevy (University of California San Diego)
DTSTART:20220201T203000Z
DTEND:20220201T213000Z
DTSTAMP:20260404T094648Z
UID:HET/26
DESCRIPTION:Title: Three-manifolds and entanglement\nby John McGreevy (University of
California San Diego) as part of Purdue HET\n\n\nAbstract\nThe Entanglemen
t Bootstrap is a program to understand liquid topological phases. The star
ting point is a single wavefunction satisfying two simple and well-motivat
ed axioms about its entanglement structure. In 2+1 dimensions\, much of t
he algebraic theory of anyons has been derived from this starting point.
In this talk\, based on work with Bowen Shi and Jin-Long Huang\, I'll desc
ribe some consequences of this line of thought in 3+1 dimensions\, where t
he richness of low-dimensional topology plays a role.\n\nSome of this work
has appeared in https://arxiv.org/abs/2112.08398.\n
LOCATION:https://stable.researchseminars.org/talk/HET/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex May (Stanford University)
DTSTART:20220208T203000Z
DTEND:20220208T213000Z
DTSTAMP:20260404T094648Z
UID:HET/27
DESCRIPTION:Title: Towards quantum information processing in gravitating spacetimes\n
by Alex May (Stanford University) as part of Purdue HET\n\n\nAbstract\nAsi
de from quantum mechanics\, other areas in physics constrain information p
rocessing. From relativity\, we know information cannot move faster than t
he speed of light. In quantum gravity\, we expect but don't fully understa
nd additional constraints\, for instance on how densely information can be
stored. Can we develop an understanding of information processing in the
context of quantum gravity? Towards doing so\, we consider quantum informa
tion within holographic spacetimes\, which have an alternative\, non-gravi
tational\, description. In that context questions about information proces
sing in the presence of gravity can be translated to different questions a
bout quantum information without gravity. As a specific example\, we study
constraints on computation within a gravitating region\, and use the holo
graphic description to argue that gravity constrains the complexity of ope
rations that can happen inside the region. Along the way\, we are led to n
ew connections relating quantum gravity\, position-based cryptography\, qu
antum secret sharing and complexity theory.\n
LOCATION:https://stable.researchseminars.org/talk/HET/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mukund Rangamani (University of California\, Davis)
DTSTART:20220215T203000Z
DTEND:20220215T213000Z
DTSTAMP:20260404T094648Z
UID:HET/28
DESCRIPTION:Title: A paradigm for open quantum systems with memory from holography\nb
y Mukund Rangamani (University of California\, Davis) as part of Purdue HE
T\n\n\nAbstract\nThe late-time\, long-distance behaviour of gravitational
perturbations of planar AdS black holes is controlled by hydrodynamic quas
inormal modes. In the dual CFT these are modes of the conserved currents w
hich control the infra-red dynamics. While the on-shell structure of these
modes has been understood for a long-time\, we have recently begun to und
erstand how to construct an off-shell low energy effective action\, an e
ffective hydrodynamic field theory\, from holography. I will describe the
general lessons learnt from the gravitational analysis\, sketching out a p
aradigm that provides a template for the analysis of general quantum syste
ms with dissipation and long-time memory.\n
LOCATION:https://stable.researchseminars.org/talk/HET/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicole Yunger Halpern (QuICS\, NIST\, University of Maryland)
DTSTART:20220308T203000Z
DTEND:20220308T213000Z
DTSTAMP:20260404T094648Z
UID:HET/29
DESCRIPTION:Title: Linear growth of quantum circuit complexity\nby Nicole Yunger Halp
ern (QuICS\, NIST\, University of Maryland) as part of Purdue HET\n\n\nAbs
tract\nQuantifying quantum states' complexity is a key problem in various
subfields of science\, from quantum computing to black-hole physics. We pr
ove a prominent conjecture by Brown and Susskind about how random quantum
circuits' complexity increases. Consider constructing a unitary from Haar-
random two-qubit quantum gates. Implementing the unitary exactly requires
a circuit of some minimal number of gates—the unitary's exact circuit co
mplexity. We prove that this complexity grows linearly with the number of
random gates\, with unit probability\, until saturating after exponentiall
y many random gates. Our proof is surprisingly short\, given the establish
ed difficulty of lower-bounding the exact circuit complexity. Our strategy
combines differential topology and elementary algebraic geometry with an
inductive construction of Clifford circuits.\n\nReferences 1) Haferkamp\,
Faist\, Kothakonda\, Eisert\, and NYH\, accepted by Nat. Phys. (in press)
arXiv:2106.05305. 2) NYH\, Kothakonda\, Haferkamp\, Munson\, Faist\, and E
isert\, arXiv:2110.11371 (2021).\n
LOCATION:https://stable.researchseminars.org/talk/HET/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Akers (MIT)
DTSTART:20220419T193000Z
DTEND:20220419T203000Z
DTSTAMP:20260404T094648Z
UID:HET/30
DESCRIPTION:Title: Black holes as non-isometric codes\nby Chris Akers (MIT) as part o
f Purdue HET\n\n\nAbstract\nThe interior of an old black hole is encoded i
n the Hawking radiation. Thisseems to be the implication of recent computa
tions of the Page curve. We takethis idea to its logical conclusion\, mode
ling old black holes as quantum codesembedding a large number of degrees o
f freedom (the interior and semiclassicalradiation) into a smaller number
(the stretched horizon and physicalradiation). I will prove that such code
s exist\, and discuss their novelproperties and what they can tell us abou
t black holes. \n
LOCATION:https://stable.researchseminars.org/talk/HET/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lampros Lamprou (University of British Columbia)
DTSTART:20220315T193000Z
DTEND:20220315T203000Z
DTSTAMP:20260404T094648Z
UID:HET/31
DESCRIPTION:Title: Falling inside holographic black holes\nby Lampros Lamprou (Univer
sity of British Columbia) as part of Purdue HET\n\n\nAbstract\nI will pres
ent a bulk reconstruction technique in AdS/CFT suitable for addressing a f
acet of the black hole information problem: how to unambiguously predict t
he results of measurements accessible to an infalling observer in the blac
k hole interior. I will explicitly apply the method in the AdS$_2$/SYK cor
respondence and comment on its generalizations.\n
LOCATION:https://stable.researchseminars.org/talk/HET/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anthony Munson (University of Maryland)
DTSTART:20220329T193000Z
DTEND:20220329T203000Z
DTSTAMP:20260404T094648Z
UID:HET/32
DESCRIPTION:Title: Quantum (Un)complexity: A Resource for Quantum Computation\nby Ant
hony Munson (University of Maryland) as part of Purdue HET\n\n\nAbstract\n
Under random dynamics\, a system’s quantum complexity—which quantifies
the difficulty of preparing a desired state from a simple\, tensor-produc
t state—increases linearly up to times exponential in the system’s siz
e\, long after most physical observables have thermalized. The observation
that complexity saturation is a late stage of quantum thermalization sugg
ests that a state’s lack of complexity\, or ``uncomplexity\,'' is a usef
ul resource for quantum computation: Much as a system far from thermal equ
ilibrium can serve as a resource in information-processing tasks\, a state
with high uncomplexity—i.e.\, a low-complexity state such as |0^n>—ca
n be utilized as ``blank scrap paper'' for quantum computers. It is natura
l\, therefore\, to view uncomplexity through the lens of a resource theory
. In a resource theory\, an agent can perform any operation subject to a f
ixed set of simple rules\, and can identify which tasks are achievable und
er these rules and which tasks require additional resources. We define a r
esource theory of uncomplexity\, and then construct protocols in the resou
rce theory for extracting uncomplexity from a state and for expending unco
mplexity to imitate a state. Moreover\, we show that a new quantity\, the
complexity entropy\, quantifies the efficiencies with which we can perform
uncomplexity extraction and expenditure\, and thereby quantifies the reso
urce requirements for one-shot thermodynamic erasure (Landauer erasure) un
der computational limitations.\n\nYunger Halpern\, Kothakonda\, Haferkamp\
, Munson\, Eisert\, and Faist (2021). https://arxiv.org/abs/2110.11371\n
LOCATION:https://stable.researchseminars.org/talk/HET/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexander Jahn (Caltech)
DTSTART:20220510T193000Z
DTEND:20220510T203000Z
DTSTAMP:20260404T094648Z
UID:HET/33
DESCRIPTION:Title: Holographic toy models with matchgate tensor networks\nby Alexande
r Jahn (Caltech) as part of Purdue HET\n\n\nAbstract\nMuch insight into th
e quantum information side of holographic dualities has come from studying
simple toy models based on tensor networks. While these models have been
shown to realize properties such as entanglement and quantum error correct
ion in line with continuum AdS/CFT\, their boundary states differ from tho
se of simple lattice discretizations of CFTs. In this talk\, I will introd
uce a class of tensor networks based on matchgate tensors for which such t
oy models can be efficiently constructed. Within this class\, we will find
simple solutions that are identified with a local\, critical boundary Ham
iltonian corresponding to a disordered version of the critical Ising model
. Rather than just ground states\, we will find that the matchgate tensor
ansatz can also reproduce low-energy excited states of the boundary Hamilt
onian\, leading to a concrete bulk-boundary dictionary between bulk and bo
undary states. I will argue that this can be extended to a new class of ho
lographic codes related to imaginary-time path integrals\, which serves as
a promising avenue to study time dynamics in holographic tensor network m
odels.\n
LOCATION:https://stable.researchseminars.org/talk/HET/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabor Sarosi (CERN)
DTSTART:20220628T193000Z
DTEND:20220628T203000Z
DTSTAMP:20260404T094648Z
UID:HET/34
DESCRIPTION:Title: Comments on the volume of the black hole interior in 2d gravity\nb
y Gabor Sarosi (CERN) as part of Purdue HET\n\n\nAbstract\nThe volume of t
he interior of a two-sided eternal black hole classically grows forever. I
will derive a microscopic formula for this volume in JT gravity by summin
g the non-perturbative contribution of higher topologies. The non-perturba
tive corrections lead to the saturation of the volume of the interior at t
imes exponential in the entropy of the black hole. I will connect the micr
oscopic formula for the volume with properties of a time averaged density
matrix\, in particular with its second Renyi entropy\, which I argue to me
asure the number of nearly orthogonal states visited by time evolution. I
will discuss various problems with this interpretation.\n
LOCATION:https://stable.researchseminars.org/talk/HET/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cesar Agon (Instituto Balseiro)
DTSTART:20220809T193000Z
DTEND:20220809T203000Z
DTSTAMP:20260404T094648Z
UID:HET/35
DESCRIPTION:Title: On the N-partite information in Conformal Field Theory\nby Cesar A
gon (Instituto Balseiro) as part of Purdue HET\n\n\nAbstract\nIn this talk
\, I will present a general procedure for computing the N-partite informat
ion in the ground state of a conformal field theory for N-disjoint spheres
in the large separation regime. I will motive this computation as part of
the general program of describing the CFT from entanglement related quant
ities. Then\, I will apply the general procedure to rederive known formula
s for the mutual information and tri-partite information as well as to pre
sent a new result pertaining the four-partite information in the large sep
aration regime. I then show good agreement between our analytic results an
d lattice computations for the free scalar field in $d=3$. Finally\, I clo
se with an explicit check within the context of our computations of the Fa
ulkner\, Lewkowycz and Maldacena (FLM) prescription in holographic conform
al field theories.\n
LOCATION:https://stable.researchseminars.org/talk/HET/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Keiichiro Furuya (Purdue University)
DTSTART:20220816T193000Z
DTEND:20220816T203000Z
DTSTAMP:20260404T094648Z
UID:HET/36
DESCRIPTION:Title: An Algebra of Observables for de Sitter Space\nby Keiichiro Furuya
(Purdue University) as part of Purdue HET\n\n\nAbstract\nIn this talk\, I
will review the latest paper\, ``An Algebra of Observables for de Sitter
Space’’. Since Bekenstein studied the entropy associated with the bla
ck hole\, the studies of the entropic structure of a system with gravity h
ave been developed. Especially\, the (entanglement) entropy of a quantum s
ystem of two different regions is important to explore the correlations in
a system. In a quantum mechanical system\, the (entanglement) entropy is
a property of the states of a given system. In quantum field theory\, it
is instead the property of the algebra of quantum field theory associated
with a subregion of spacetime\, which we now call the local algebra. In pa
rticular\, the ultraviolet divergence is due to the property of the local
algebra. Hence\, understanding the entropic structure of quantum field the
ory requires you to investigate the structure of a local algebra. This pap
er specifies the properties of the local algebra of quantum field theory i
n de Sitter space to seek its entropy.\n
LOCATION:https://stable.researchseminars.org/talk/HET/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Javier Magan (University of Pennsylvania)
DTSTART:20221005T193000Z
DTEND:20221005T203000Z
DTSTAMP:20260404T094648Z
UID:HET/37
DESCRIPTION:Title: A tale of two hungarians: tridiagonalizing random matrices\nby Jav
ier Magan (University of Pennsylvania) as part of Purdue HET\n\n\nAbstract
\nThe Hungarian physicist Eugene Wigner introduced random matrix models in
physics to describe the energy spectra of atomic nuclei. As such\, the ma
in goal of Random Matrix Theory (RMT) has been to derive the eigenvalue st
atistics of matrices drawn from a given distribution. The Wigner approach
gives powerful insights into the properties of complex\, chaotic systems i
n thermal equilibrium. Another Hungarian\, Cornelius Lanczos\, suggested
a method of reducing the dynamics of any quantum system to a one-dimension
al chain by tridiagonalizing the Hamiltonian relative to a given initial s
tate. In the resulting matrix\, the diagonal and off-diagonal Lanczos coef
ficients control transition amplitudes between elements of a distinguished
basis of states. This method suggests a computable notion of complexity w
hich we describe in detail. We then connect the Wigner/Lanczos approaches
by analyzing RMT in time-dependent scenarios. This is first accomplished
by numerically studying time-evolved thermofield double states in chaotic
systems\, where our complexity measure shows parallel regimes as the Spect
ral Form Factor in RMT. Secondly\, to approach these problems analytically
\, we initiate a novel approach to Random Matrix Theory based on matrix tr
idiagonzalition\, deriving the statistics of the tridiagonal matrix.\n
LOCATION:https://stable.researchseminars.org/talk/HET/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Julian Sonner (University of Geneva)
DTSTART:20221018T193000Z
DTEND:20221018T203000Z
DTSTAMP:20260404T094648Z
UID:HET/38
DESCRIPTION:Title: Matrix Models for Eigenstate Thermalization with applications to holog
raphy\nby Julian Sonner (University of Geneva) as part of Purdue HET\n
\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/HET/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Samuel Leutheusser (MIT)
DTSTART:20221025T193000Z
DTEND:20221025T203000Z
DTSTAMP:20260404T094648Z
UID:HET/39
DESCRIPTION:Title: Subregion-subalgebra duality and the emergence of space and time in ho
lography\nby Samuel Leutheusser (MIT) as part of Purdue HET\n\n\nAbstr
act\nIn holographic duality a higher dimensional quantum gravity system em
erges from a lower dimensional conformal field theory (CFT) with a large n
umber of degrees of freedom\, N. Bulk geometric notions such as spacetime
subregions\, extremal surfaces\, and causal structure are only sharply def
ined in the bulk G_N \\to 0 limit which corresponds to the boundary N \\to
\\infty limit. In this talk\, we will argue that geometric notions in the
bulk emerge from the mathematical structure of the large N limit of the d
ual CFT\, which we have shown gives rise to the ubiquitous emergence of ty
pe III_1 von Neumann algebras. We explicitly construct the boundary subalg
ebras that describe bulk physics in most bulk subregions. We also comment
on the relationship of our construction with quantum error correction\, su
bregion-subregion duality and the RT prescription.\n
LOCATION:https://stable.researchseminars.org/talk/HET/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Antony Speranza (UIUC)
DTSTART:20221115T203000Z
DTEND:20221115T213000Z
DTSTAMP:20260404T094648Z
UID:HET/40
DESCRIPTION:Title: Complexity = (Anything)^2\nby Antony Speranza (UIUC) as part of Pu
rdue HET\n\nLecture held in Room 242\, Department of Physics and Astronomy
\, Purdue University.\n\nAbstract\nI will describe an infinite class of gr
avitational observables that can serve as measures of holographic complexi
ty. These observables are constructed relationally by extremizing a surfa
ce with respect to one functional\, and evaluating a second functional on
that surface. We show that classical Poisson brackets of these observable
s can be computed via the Peierls construction\, and demonstrate that the
extremality conditions follow naturally from diffeomorphism invariance. A
wide class of these observables can be shown to exhibit universal propert
ies of complexity measures\, including linear growth at late times in ther
mal states and the switchback effect. By taking distinct limits\, specifi
c observables can be shown to reduce to the standard holographic complexit
y measures such as volume or action.\n
LOCATION:https://stable.researchseminars.org/talk/HET/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pawel Caputa (University of Warsaw)
DTSTART:20221101T193000Z
DTEND:20221101T203000Z
DTSTAMP:20260404T094648Z
UID:HET/41
DESCRIPTION:Title: Quantum Complexity in the Krylov basis\nby Pawel Caputa (Universit
y of Warsaw) as part of Purdue HET\n\n\nAbstract\nI will review some recen
t progress on defining a universal measure of quantum complexity based on
the so-called Krylov basis. After introducing Krylov basis techniques\, I
will discuss the “Spread Complexity” measure for quantum states with s
ome explicit examples its general properties. The talk will be based on:\n
https://arxiv.org/abs/2202.06957\nhttps://arxiv.org/abs/2109.03824\n
LOCATION:https://stable.researchseminars.org/talk/HET/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Erik Tonni (SISSA and INFN Sezione di Trieste)
DTSTART:20221122T203000Z
DTEND:20221122T213000Z
DTSTAMP:20260404T094648Z
UID:HET/42
DESCRIPTION:Title: Entanglement entropies for Lifshitz fermionic fields at finite density
\nby Erik Tonni (SISSA and INFN Sezione di Trieste) as part of Purdue
HET\n\n\nAbstract\nThe entanglement entropies of an interval for the free
fermionic spinless Schroedinger field theory at finite density and zero te
mperature are investigated. The interval is either on the line or at the b
eginning of the half line\, when either Neumann or Dirichlet boundary cond
itions are imposed at the origin. We show that the entanglement entropies
are finite functions of a dimensionless parameter proportional to the area
of the rectangular region in the phase space identified by the Fermi mome
ntum and the length of the interval. \nFor the interval on the line\, the
entanglement entropy is a monotonically increasing function. Instead\, for
the interval on the half line\, it displays an oscillatory behaviour rela
ted to the Friedel oscillations of the mean particle density at the entang
ling point. \nBy employing the properties of the prolate spheroidal wave f
unctions or the expansions of the tau functions of the kernels occurring i
n the spectral problems\, determined by the two point function\, we find a
nalytic expressions for the expansions of the entanglement entropies in th
e asymptotic regimes of small and large area of the rectangular phase spac
e region. Extending our analysis to a class of free fermionic Lifshitz mod
els\, we find that the parity of the Lifshitz exponent determines the prop
erties of the bipartite entanglement.\n
LOCATION:https://stable.researchseminars.org/talk/HET/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Tomamichel (National University of Singapore)
DTSTART:20220920T140000Z
DTEND:20220920T150000Z
DTSTAMP:20260404T094648Z
UID:HET/43
DESCRIPTION:Title: Quantum Rényi divergence and beyond\nby Marco Tomamichel (Nationa
l University of Singapore) as part of Purdue HET\n\n\nAbstract\nI will giv
e a tour of quantum generalisations of Rényi's entropy and divergence and
various notions of conditional entropy and mutual information based on R
ényi divergence. A particular focus will be on the non-uniqueness of such
generalisations and interesting questions that arise from it\, as well as
operational interpretations of some Rényi information measures.\n
LOCATION:https://stable.researchseminars.org/talk/HET/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shoy Ouseph (Purdue University)
DTSTART:20221108T203000Z
DTEND:20221108T213000Z
DTSTAMP:20260404T094648Z
UID:HET/44
DESCRIPTION:Title: Recent developments in generalizing symmetries\nby Shoy Ouseph (Pu
rdue University) as part of Purdue HET\n\n\nAbstract\nI will be reviewing
the recent developments in understanding symmetries in quantum many body s
ystems and generalizing the Landau theory for phase transitions based on t
he review paper https://arxiv.org/abs/2204.03045 and https://arxiv.org/abs
/1412.5148.\n
LOCATION:https://stable.researchseminars.org/talk/HET/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Prashanth Raman (Indian Institute of Science)
DTSTART:20220927T193000Z
DTEND:20220927T203000Z
DTSTAMP:20260404T094648Z
UID:HET/45
DESCRIPTION:Title: Positivity Constraints on EFT’s and Geometric Function Theory\nb
y Prashanth Raman (Indian Institute of Science) as part of Purdue HET\n\nL
ecture held in Room 242\, Department of Physics and Astronomy.\n\nAbstract
\nIn this talk\, we shall look at the implications of crossing symmetry\,
locality\, and unitarity in the UV on low-energy EFT’s. We will begin by
looking at 2-2scattering amplitudes with identical external particles and
introduce a crossing symmetric dispersive representation (CSDR) of the am
plitude that makes full (s\,t\,u)-crossing symmetry manifest\, unlike the
usual fixed-t dispersion relations. Though the CSDR makes crossing symmetr
y manifest\, locality is lost and has to be restored by demanding that cer
tain spurious singularities cancel in the low energy expansion of the ampl
itude leading to locality constraints. \n\nFor massive external particles\
, the CSDR and unitarity make a certain analytic property of the amplitude
called typically-realness manifest and enables us to use techniques from
the geometric function theory of typically-real functions to show that the
low energy Wilson coefficients have to be o(1) numbers and that the space
of these Wilson coefficients is finite. \nFor massless external particle
s with massive exchanges we look at the celestial amplitude (CA) correspon
ding to our original 2-2 scattering amplitude and show that the locality c
onstraints imply an infinite linear system of equations that the partial w
ave moments of any local theory need to satisfy. By additionally imposing
linear unitarity (positivity of partial wave moments)\, we show that these
naturally lead to the phenomenon of low-spin dominance (LSD). Finally\,
we show that the crossing symmetric partial waves with spurious singularit
ies removed\, dubbed as Feynman blocks are typically-real and using this w
e obtain two-sided bounds on low-energy Wilson coefficients for this case.
\nThis is based on work with Sudip Ghosh and Aninda Sinha.\n\nHost: Martin
Kruczenski\n
LOCATION:https://stable.researchseminars.org/talk/HET/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nathan Benjamin (CalTech)
DTSTART:20221129T203000Z
DTEND:20221129T213000Z
DTSTAMP:20260404T094648Z
UID:HET/46
DESCRIPTION:Title: Scalar Modular Bootstrap and Zeros of the Riemann Zeta Function\nb
y Nathan Benjamin (CalTech) as part of Purdue HET\n\nLecture held in Room
242\, Department of Physics and Astronomy.\n\nAbstract\nWe derive a crossi
ng equation that acts only on the scalar primary operators of any 2d CFT w
ith U(1)^c symmetry. We derive bounds on the scalar gap of all such theori
es. Rather remarkably\, our crossing equation contains information about a
ll nontrivial zeros of the Riemann zeta function. As a result\, we rephras
e the Riemann hypothesis as a statement about the asymptotic density of sc
alar operators in certain theories. We discuss generalizations to theories
with only Virasoro symmetry. Based on 2208.02259 with C.-H. Chang.\n
LOCATION:https://stable.researchseminars.org/talk/HET/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roy Araiza (UIUC)
DTSTART:20230404T193000Z
DTEND:20230404T203000Z
DTSTAMP:20260404T094648Z
UID:HET/47
DESCRIPTION:Title: An index for inclusions of operator systems\nby Roy Araiza (UIUC)
as part of Purdue HET\n\nLecture held in Room 242\, Department of Physics
and Astronomy.\n\nAbstract\nMotivated by the initial work of Jones\, Pimsn
er\, and Popa in studying the index of inclusions of II_1 factors\, I will
present an analogue to the ``classical index'' in the operator system cat
egory. After going through some background and initial motivation\, our go
al will be to connect this new ``completely positive index’’ of operat
or systems arising from finite graphs\, to the Lovasz theta invariant.\n
LOCATION:https://stable.researchseminars.org/talk/HET/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yidong Chen (UIUC)
DTSTART:20230411T193000Z
DTEND:20230411T203000Z
DTSTAMP:20260404T094648Z
UID:HET/48
DESCRIPTION:Title: Noncommutative Poisson Random Measure and its Applications in AQFT and
Quantum Chaos\nby Yidong Chen (UIUC) as part of Purdue HET\n\n\nAbstr
act\nOne of the important problems in modern mathematical physics is to un
derstand quantization - both quantizing classical systems to quantum syste
ms and quantizing one-particle systems to many-body systems. Up to now\, t
he mathematical second quantization relies on the Gaussian functor and pro
duces generalized free theories. Interactions are generally modeled by per
turbation theories (a la Glimm and Jaffe). In this talk\, we take a new ap
proach to second quantization by constructing a noncommutative analog of t
he classical Poisson random measure. This construction produces a functor
which shall be called Poissonization. The analog of correlation functions
in this construction cannot be factorized into the sum of products of two-
point functions. After we outlined the main ideas of Poissonization\, we w
ill clearly state the construction and its functorial properties. Moreover
\, we will discuss the main properties of this construction\, emphasizing
on its versatility and physical relevance. Subsequently\, we will focus on
two main areas of physical applications. On one hand\, we will discuss ho
w Poissonization can be used to produce examples of algebraic quantum fiel
d theories starting from the data of unitary representations of real semis
imple Lie groups (single particles a la Weinberg). On the other hand\, we
will discuss how Poissonization can be used to rigorously calculate quantu
m information quantities (e.g. relative entropy\, tripartite information\,
out-of-time-order correlation etc.) in type III von Neumann algebras. In
many toy examples\, these quantities have the right quanlitative behaviors
as conjectured in physics literature. Lastly\, we will briefly discuss fu
ture directions\, emphasizing on why we cannot yet claim to have construct
ed an interacting CFT in dimensions larger than 2 and how we can achieve t
his goal using Poissonization.\n
LOCATION:https://stable.researchseminars.org/talk/HET/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicholas LaRacuente (University of Chicago)
DTSTART:20230418T193000Z
DTEND:20230418T203000Z
DTSTAMP:20260404T094648Z
UID:HET/49
DESCRIPTION:Title: Complexity and Purity Over Time in Quantum Dynamics\nby Nicholas L
aRacuente (University of Chicago) as part of Purdue HET\n\nLecture held in
Room 242\, Department of Physics and Astronomy.\n\nAbstract\nA quantum sy
stem's time-evolution usually combines internal\, coherent dynamics with e
nvironmental noise. Combined dynamics may converge to mixed equilibria\, r
educe to classical determinism for long times\, or maintain non-classicali
ty. The first regime is well-explained in quantum Markov semigroup theory.
The second is well-established in classical mechanics\, though its emerge
nce from quantum dynamics still yields mysteries. The third regime of pers
istent quantum complexity is a key goal\, often proposed achievable throug
h active error correction. I will present results on the capabilities for
quantum quench dynamics to innately manifest non-classical complexities an
d maintain classical or quantum purity without intervention. Of particular
interest are chaotic quantum systems and related conjectures about natura
l phenomena seeming to require non-classical capabilities.\n
LOCATION:https://stable.researchseminars.org/talk/HET/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonah Kudler-Flam (IAS Princeton)
DTSTART:20230425T193000Z
DTEND:20230425T203000Z
DTSTAMP:20260404T094648Z
UID:HET/50
DESCRIPTION:Title: Horizons as eavesdroppers: decoherence from soft radiation\nby Jon
ah Kudler-Flam (IAS Princeton) as part of Purdue HET\n\n\nAbstract\nRecent
ly\, Danielson\, Satishchandran\, and Wald proposed a novel mechanism for
decoherence in spacetimes with Killing horizons. When Alice performs a Ste
rn-Gerlach type experiment outside the horizon\, there is a fundamental ra
te of decoherence due to the emission of soft gravitons/photons that radia
te away information. In this talk\, I will sharpen and generalize this mec
hanism by recasting the gedankenexperiment in the language of (approximate
) quantum error correction. By explicitly computing the quantum fidelity b
etween the vacuum state on the horizon and the state with soft radiation p
ropagating through the horizon\, we characterize how much an eavesdropper
(Eve) behind the horizon is able to learn about Alice's experiment. From t
he information-disturbance tradeoff\, there is a direct relation between t
he information gained by Eve and the decoherence of Alice's generalized ex
periment. I will comment on how an information-theoretic language may lead
to new insights on energy/entropy inequalities\, islands\, and the centra
l dogma of black holes.\n
LOCATION:https://stable.researchseminars.org/talk/HET/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dalimil Mazac (IAS Princeton)
DTSTART:20230502T193000Z
DTEND:20230502T203000Z
DTSTAMP:20260404T094648Z
UID:HET/51
DESCRIPTION:Title: Conformal measure spaces\nby Dalimil Mazac (IAS Princeton) as part
of Purdue HET\n\n\nAbstract\nThe conformal bootstrap equations in the gen
eral dimension are an infinite set of coupled non-linear equations in infi
nitely many variables. According to the lore\, the solutions of the full s
et of equations correspond to physical CFTs. At the same time\, the only s
olutions truly known to exist above two dimensions are the mean field theo
ries. In this talk\, I will define conformal measure spaces\, which are ma
thematical objects guaranteed to produce solutions of the conformal bootst
rap in any dimension. I will review why hyperbolic manifolds give rise to
a particular class of conformal measure spaces\, and use the bootstrap equ
ations to prove new bounds on their spectra. Finally\, I will discuss the
similarities and differences between these solutions\, and those that are
believed to arise in physical CFTs.\n
LOCATION:https://stable.researchseminars.org/talk/HET/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Samuel Goldman (UIUC)
DTSTART:20230509T193000Z
DTEND:20230509T203000Z
DTSTAMP:20260404T094648Z
UID:HET/52
DESCRIPTION:Title: Exact Renormalization and its Application to Quantum States\nby Sa
muel Goldman (UIUC) as part of Purdue HET\n\n\nAbstract\nThe exact renorma
lization group (ERG) is a general tool for implementing the Wilsonian idea
that physics is independent of our parametrization of the degrees of free
dom. In its original formulation\, it is simply a manifestation of the inv
ariance of path integrals with respect to the choice of field variable. Mo
re recently\, ERG methods have been generalized to objects derived from pa
th integrals\, such as wavefunctionals. We extend these ideas in two compl
ementary ways which demonstrate the flexibility of ERG\n\nin the context o
f quantum states. In one scheme which uses multiple regulators\, we obtain
a class of unitary wavefunctional flows\, a subset of which are the so-ca
lled continuous MERA networks. In a parallel investigation\, we consider t
he ERG for density operators and find that the non-locality generated alon
g flows introduces non-unitary contributions to the state. The description
of this non-unitarity takes the form of a quantum Markov semigroup. These
results have a variety of potential applications\, such as the constructi
on of interacting and non-unitary cMERA networks\, as well as extending ou
r understanding of emergent geometry and renormalization in both holograph
ic and non-holographic contexts.\n
LOCATION:https://stable.researchseminars.org/talk/HET/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Zhencheng Wang (UIUC)
DTSTART:20240123T203000Z
DTEND:20240123T213000Z
DTSTAMP:20260404T094648Z
UID:HET/53
DESCRIPTION:Title: Type I von Neumann algebras from gravitational path integrals\nby
Zhencheng Wang (UIUC) as part of Purdue HET\n\nLecture held in Room 242 in
the Department of Physics and Astronomy.\n\nAbstract\nIn this talk\, I wi
ll describe a construction of Hilbert spaces and von Neumann algebras from
any UV-completion of asymptotically anti-de Sitter quantum gravity with a
Euclidean path integral satisfying a simple and familiar set of axioms. W
e consider a quantum context in which a standard Lorentz-signature classic
al bulk limit would have Cauchy slices with two asymptotic boundaries (lef
t and right)\, both of which are compact manifolds without boundary. Our m
ain result is then that the quantum gravity path integral defines (left an
d right) type I von Neumann algebras of observables acting respectively at
the left and right boundaries\, such that the two algebras are commutants
. The path integral also defines entropies on the von Neumann algebras. Th
e entropies can also be written in terms of standard density matrices and
standard Hilbert space traces.\n
LOCATION:https://stable.researchseminars.org/talk/HET/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ning Bao (Northeastern University)
DTSTART:20240220T203000Z
DTEND:20240220T213000Z
DTSTAMP:20260404T094648Z
UID:HET/54
DESCRIPTION:Title: An Exponential Speedup in Contraction Maps for Holographic Entanglemen
t Entropy\nby Ning Bao (Northeastern University) as part of Purdue HET
\n\n\nAbstract\nIn this talk\, I will go over the basic concepts of contra
ction map proof methods for holographic entanglement entropy\, and comment
on recent advances in dramatically improving the proving power of such in
equalities. In addition\, I will prove the completeness of such methods.\n
LOCATION:https://stable.researchseminars.org/talk/HET/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Arvin Shahbazi-Moghaddam (Stanford)
DTSTART:20240305T203000Z
DTEND:20240305T213000Z
DTSTAMP:20260404T094648Z
UID:HET/55
DESCRIPTION:Title: Singular inner horizons\nby Arvin Shahbazi-Moghaddam (Stanford) as
part of Purdue HET\n\nLecture held in Room 242 in the Department of Physi
cs and Astronomy.\n\nAbstract\nAn often overlooked problem in black hole p
hysics is that the inner horizon of stationary black holes do not (generic
ally) exist even in the equilibrium state (i.e. the Hartle-Hawking state)\
, due to the divergence of quantum fields. Even though this behavior has b
een observed numerically in 2+1 and 3+1 dimensions for free fields\, a uni
versal and analytic understanding of it is lacking. I will discuss work in
progress on trying to fill this gap.\n
LOCATION:https://stable.researchseminars.org/talk/HET/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sridip Pal (Caltech)
DTSTART:20240312T193000Z
DTEND:20240312T203000Z
DTSTAMP:20260404T094648Z
UID:HET/56
DESCRIPTION:Title: Universality in Spin-resolved High-Energy CFT data\nby Sridip Pal
(Caltech) as part of Purdue HET\n\nLecture held in Room 242 in the Departm
ent of Physics and Astronomy.\n\nAbstract\nI will discuss the universal be
havior of spin-resolved data of conformal field theory (CFT) at high energ
ies. Using a technique\, called thermal effective field theory\, we derive
\, for d>2 CFTs\, the universal high temperature behavior of grand-canonic
al partition function with finite angular fugacity turned on. This result
can be considered a higher-dimensional version of a similar formula for 2d
CFTs\, generally derived using modular invariance. I will also discuss ho
lographic interpretations of this result.\n
LOCATION:https://stable.researchseminars.org/talk/HET/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Agnese Bissi (ICTP Trieste)
DTSTART:20240326T183000Z
DTEND:20240326T193000Z
DTSTAMP:20260404T094648Z
UID:HET/57
DESCRIPTION:Title: Multi-trace operators in CFTs\nby Agnese Bissi (ICTP Trieste) as p
art of Purdue HET\n\n\nAbstract\nIn this talk I will discuss how to deal w
ith multi-trace operators\, in particular in the context of N=4 Super Yang
Mills. I will review their relevance in computing holographic correlators
and discuss recent developments on how to treat them.\n
LOCATION:https://stable.researchseminars.org/talk/HET/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anatoly Dymarsky (University of Kentucky)
DTSTART:20240402T193000Z
DTEND:20240402T203000Z
DTSTAMP:20260404T094648Z
UID:HET/58
DESCRIPTION:Title: Classical and quantum codes\, 2d CFTs and holography\nby Anatoly D
ymarsky (University of Kentucky) as part of Purdue HET\n\nLecture held in
Room 242 in the Department of Physics and Astronomy.\n\nAbstract\nThere is
a rich connection between classical and quantum codes and holographic cor
respondence connecting 2d CFTs and abelian 3d Chern-Simons theories. In th
e 3d language the codes emerge as a way to parametrize condensable anyons.
Upon condensation 3d topological field theory gives rise to 2d CFT at\n t
he boundary. This provides a way to construct 2d CFTs from codes - the so-
called "code CFTs". This construction has a natural interpretation in term
s of a CSS quantum code (defined in terms of the original classical code\,
defining the CFT). From the holographic point of view a particularly inte
resting question is that of an ensemble of codes and associated code CFTs.
The ensemble of boundary theories is holographically dual to "Chern-Simon
s gravity"\, a topological field theory that sums over 3d topologies.\n
LOCATION:https://stable.researchseminars.org/talk/HET/58/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Green (UCSD)
DTSTART:20240430T193000Z
DTEND:20240430T203000Z
DTSTAMP:20260404T094648Z
UID:HET/59
DESCRIPTION:Title: Cosmic Surveys and the Quantum Universe\nby Daniel Green (UCSD) as
part of Purdue HET\n\nLecture held in Room 242.\n\nAbstract\nUnderstandin
g the quantum nature of accelerating cosmologies is essential to making se
nse of the past\, present\, and future of our Universe. One important quan
tity relevant to the dynamics of these epoches is the spectrum of quantum
fluctuations\, organized by scaling dimensions that control how these fluc
tuations redshift away. When these fluctuations are coupled to the inflat
on in the early universe\, this scaling behavior appears in the statistics
of the density fluctuations and can be measured with galaxy surveys. Rema
rkably\, self-consistency of these late universe observations with the sym
metries of the early universe place non-trivial constraints on both the dy
namics of inflation and the statistics of galaxies. In this talk\, I will
explain how these connections arise\, what they can tell us about the Univ
erse\, and the current constraints and future prospects for measuring thes
e dimensions with cosmic surveys.\n
LOCATION:https://stable.researchseminars.org/talk/HET/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yikun Jiang (Northeastern University)
DTSTART:20240507T193000Z
DTEND:20240507T203000Z
DTSTAMP:20260404T094648Z
UID:HET/60
DESCRIPTION:Title: Building up quantum spacetimes with BCFT Legos\nby Yikun Jiang (No
rtheastern University) as part of Purdue HET\n\nLecture held in Room 350 i
n the Department of Physics and Astronomy.\n\nAbstract\nIs it possible to
read off the quantum gravity dual of a CFT directly from its operator alge
bra? In this talk\, I will present a step-by-step recipe for building up 3
D quantum spacetimes dual to 2D CFTs\, synthesizing results and techniques
from conformal bootstrap\, topological symmetries\, real-space tensor net
work renormalization\, and the asymptotics of quantum 6j symbols. Quantum
Liouville theory serves as a simple and explicit example\, illustrating ho
w the exact CFT/gravitational path integral can be built up from triangula
tion and local pieces of BCFT correlation functions\, which we call the ``
BCFT Legos''. This is essentially a tensor network that admits an interpre
tation of a state-sum of a 3D topological theory constructed with quantum
6j symbols of Uq(SL(2\,R)) with non-trivial boundary conditions\, and it r
educes to a sum over 3D geometries weighted by the Einstein-Hilbert action
to leading order in large c. The triangulation coincides with producing a
network of geodesics in the AdS bulk\, which can be changed making use of
the pentagon identity and orthogonality condition satisfied by the 6j sym
bols\, and arranged into a precise holographic tensor network. The constru
ctive map between gravity and CFT naturally and explicitly bridges local g
eometrical data\, algebraic structures\, and quantum entanglement.\n
LOCATION:https://stable.researchseminars.org/talk/HET/60/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gautam Satishchandran (Princeton University)
DTSTART:20250305T181500Z
DTEND:20250305T193000Z
DTSTAMP:20260404T094648Z
UID:HET/61
DESCRIPTION:Title: Generalized Entropy is von Neumann Entropy: Black Holes and Cosmology<
/a>\nby Gautam Satishchandran (Princeton University) as part of Purdue HET
\n\nLecture held in Room 242 in the Department of Physics and Astronomy.\n
Abstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/HET/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Sorce (MIT)
DTSTART:20250326T171500Z
DTEND:20250326T183000Z
DTSTAMP:20260404T094648Z
UID:HET/62
DESCRIPTION:Title: Gravitational constraints\, modular flow\, and the information theory
of UV divergences\nby Jonathan Sorce (MIT) as part of Purdue HET\n\nLe
cture held in Room 242 in the Department of Physics and Astronomy.\nAbstra
ct: TBA\n
LOCATION:https://stable.researchseminars.org/talk/HET/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Benoit Collins (Kyoto University)
DTSTART:20250402T140000Z
DTEND:20250402T151500Z
DTSTAMP:20260404T094648Z
UID:HET/63
DESCRIPTION:Title: Free probability and its applications to quantum information theory\nby Benoit Collins (Kyoto University) as part of Purdue HET\n\nLecture h
eld in Room 242 in the Department of Physics and Astronomy.\nAbstract: TBA
\n
LOCATION:https://stable.researchseminars.org/talk/HET/63/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Kapec (Harvard University)
DTSTART:20250423T171500Z
DTEND:20250423T183000Z
DTSTAMP:20260404T094648Z
UID:HET/64
DESCRIPTION:by Daniel Kapec (Harvard University) as part of Purdue HET\n\n
Lecture held in Room 242 in the Department of Physics and Astronomy.\nAbst
ract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/HET/64/
END:VEVENT
END:VCALENDAR