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BEGIN:VEVENT
SUMMARY:Mark van Raamsdonk (UBC)
DTSTART:20200429T150000Z
DTEND:20200429T170000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/1
DESCRIPTION:Title: Pushing boundaries in holography\nby Mark van Raamsdo
nk (UBC) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nIn this talk\,
I'll discuss a variety of applications in AdS/CFT that make use of CFTs li
ving on spacetimes with boundaries. The applications include the construct
ion of black hole microstates whose behind-the-horizon geometries can be u
nderstood explicitly\, constructing models of evaporating black holes in w
hich the Page curve can be understood through explicit CFT calculations\,
providing a microscopic descriptions of certain Randall-Sundrum scenarios\
, and providing a framework for holography where the CFT is replaced by a
large number of non-interacting "bits".\n\nYou can access the recording ri
ght here: https://www.youtube.com/watch?v=GSi4sE49gu0 .\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuela Kulaxizi (Trinity College Dublin)
DTSTART:20200506T130000Z
DTEND:20200506T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/2
DESCRIPTION:Title: Stress Tensor Sector of Conformal Correlators\nby Man
uela Kulaxizi (Trinity College Dublin) as part of GQFI-UGent-WST Seminars\
n\n\nAbstract\nAn important part of a CFT four-point function\, the stress
tensor sector\, comprises the exchanges of the stress tensor and its comp
osites. The OPE coefficients of these multi-stress tensor operators and co
nsequently\, the complete stress tensor sector of four-point functions in
CFTs with a large central charge\, can be determined by computing a heavy-
heavy-light-light correlator. We show how one can make substantial progres
s in this direction by bootstrapping a certain Ansatz for the stress tenso
r sector of the correlator\, iteratively computing the OPE coefficients of
multi-stress tensor operators with increasing twist. Some parameters are
not fixed by the bootstrap - they correspond to the OPE coefficients of mu
lti-stress tensors with spin zero and two. We further show that in hologra
phic CFTs one can use the phase shift computed in the dual gravitational t
heory to reduce the set of undetermined parameters to the OPE coefficients
of multi-stress tensors with spin zero. Finally\, we verify some of these
results using the Lorentzian OPE inversion formula and comment on its reg
ime of applicability.\n\nCorrect link: https://mpi-aei.zoom.us/j/96444244
925.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nabil Iqbal (Durham)
DTSTART:20200513T130000Z
DTEND:20200513T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/3
DESCRIPTION:Title: Toward a 3d Ising Model with a weakly coupled string dual
\nby Nabil Iqbal (Durham) as part of GQFI-UGent-WST Seminars\n\n\nAbst
ract\nIt has long been expected that the 3d Ising model can be thought of
as a string theory\, where one interprets the domain walls that separate u
p spins from down spins as two-dimensional string worldsheets. I will revi
sit this 'string theory' from the modern point of view of higher form symm
etries. The usual Ising Hamiltonian measures the area of these domain wall
s\; as there is no explicit dependence on the genus of the domain walls\,
it can be thought of as a string theory with string coupling equal to unit
y. I discuss how to add new local terms to the Ising Hamiltonian that furt
her weight each spin configuration by a factor depending on the genus of t
he corresponding domain wall\, resulting in a new 3d Ising model that has
a tunable bare string coupling. I will use a combination of analytical and
numerical methods to analyze the phase structure of this model as this st
ring coupling is varied. I will also describe statistical properties of th
e topology of worldsheets and speculate on the prospects of using this new
deformation at weak string coupling to find a worldsheet description of t
he 3d Ising transition.\n\nZoom link: https://mpi-aei.zoom.us/j/9198183751
6 .\n\n1) Please display your name when you join the seminar.\n\n2) Your m
icrophone is muted by default. Please only unmute it if you wish to make a
question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Hunter-Jones (IQI\, Perimeter)
DTSTART:20200520T140000Z
DTEND:20200520T153000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/4
DESCRIPTION:Title: Models of quantum complexity growth\nby Nick Hunter-J
ones (IQI\, Perimeter) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nA
bstract: The quantum complexity of a unitary or state is defined as the si
ze of the shortest quantum computation that implements the unitary or prep
ares the state. The notion has far-reaching implications spanning computer
science\, quantum many-body physics\, and high energy theory. Complexity
growth in time is a phenomenon expected to occur in holographic theories a
nd strongly-interacting many-body systems more generally\, but explicitly
computing the complexity of a given state or unitary is notoriously diffic
ult. By considering an ensemble of systems\, and establishing a rigorous r
elation between complexity and unitary designs\, we will prove statements
about complexity growth in various models. Specifically\, we prove a linea
r growth of complexity in random quantum circuits\, using a recent result
about their design growth. \n\nZoom Link: https://mpi-aei.zoom.us/j/990646
35917\n\n-----\n1) Please display your name when you join the seminar.\n2)
Your microphone is muted by default. Please only unmute it if you wish to
make a question or comment\, and then mute it back again.\n------\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ki-Seok Kim (POSTECH\, Pohang)
DTSTART:20200527T130000Z
DTEND:20200527T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/5
DESCRIPTION:Title: Emergent holographic dual effective field theory as a mea
n-field theory with all-loop quantum corrections in the large N limit\
nby Ki-Seok Kim (POSTECH\, Pohang) as part of GQFI-UGent-WST Seminars\n\n\
nAbstract\nHolographic duality conjecture states that a D-dimensional quan
tum field theory can be duality-mapped into a (D+1)-dimensional quantum gr
avity theory\, where the quantum gravity theory is a “hologram” of the
quantum field theory. Although this holographic duality conjecture serves
as a novel non-perturbative theoretical framework for strongly coupled qu
antum field theories\, the duality transformation has not been clarified u
ntil now. In this study we propose a prescription for the holographic dual
ity transformation based on Wilsonian recursive renormalization group (RG)
transformations. As a result\, we manifest the RG flow of an effective fi
eld theory with the introduction of an emergent extra dimensional space\,
where RG $\\beta$-functions to describe the evolution of coupling function
s appear in the resulting effective action explicitly through the extra di
mensional space. This microscopic construction of the dual holographic map
ping suggests that the origin of non-perturbative physics is in intertwine
d renormalization between dynamics and geometry.\n\n-----\n\n1) Please dis
play your name when you join the seminar.\n\n2) Your microphone is muted b
y default. Please only unmute it if you wish to make a question or comment
\, and then mute it back again.\n\n------\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pascal Fries (Julius-Maximilians-Universität Würzburg)
DTSTART:20200615T130000Z
DTEND:20200615T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/6
DESCRIPTION:Title: Relative Entropy and Symmetry in QFT\nby Pascal Fries
(Julius-Maximilians-Universität Würzburg) as part of GQFI-UGent-WST Sem
inars\n\n\nAbstract\nIn quantum information theory\, relative von Neumann
entropy gives a quantitative meaning for the "distinguishability" of state
s by measurements. In this talk\, I will introduce a variant of relative e
ntropy which is compatible with the existence of conserved charges. I will
show how to compute this "symmetry resolved relative entropy" in quantum
field theory and further present some analytic results for the free fermio
n CFT. This work is done in collaboration with Ignacio Reyes at AEI Potsda
m.\n\n1) Please display your name when you join the seminar.\n\n2) Your mi
crophone is muted by default. Please only unmute it if you wish to make a
question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kevin Grosvenor (Julius-Maximilians-Universität Würzburg)
DTSTART:20200617T130000Z
DTEND:20200617T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/7
DESCRIPTION:Title: Information geometry in QFT\nby Kevin Grosvenor (Juli
us-Maximilians-Universität Würzburg) as part of GQFI-UGent-WST Seminars\
n\n\nAbstract\nWe study the Fisher metrics associated with a variety of si
mple systems and derive some general lessons that may have important impli
cations for the application of information geometry in holography. Some s
ample systems of interest are the classical 2d Ising model and the corres
ponding 1d free fermion theory\, the instantons in 3+1d massless phi-four
th theory\, and coherent states of free bosons and fermions.\n\nZoom Link:
https://mpi-aei.zoom.us/j/97089841078.\n\n-----\n\n1) Please display your
name when you join the seminar.\n\n2) Your microphone is muted by default
. Please only unmute it if you wish to make a question or comment\, and th
en mute it back again.\n\n------\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Arjun Kar (University of Pennsylvania)
DTSTART:20200624T130000Z
DTEND:20200624T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/8
DESCRIPTION:Title: Geometric secret sharing in a model of Hawking radiation<
/a>\nby Arjun Kar (University of Pennsylvania) as part of GQFI-UGent-WST S
eminars\n\n\nAbstract\nWe consider a black hole in three dimensional AdS s
pace entangled with an auxiliary radiation system. We model the microstate
s of the black hole in terms of a field theory living on an end of the wor
ld brane behind the horizon\, and allow this field theory to itself have a
holographic dual geometry. This geometry is also a black hole since entan
glement of the microstates with the radiation leaves them in a mixed state
. This "inception black hole" can be purified by entanglement through a wo
rmhole with an auxiliary system which is naturally identified with the ext
ernal radiation\, giving a realization of the ER=EPR scenario. In this con
text\, we propose an extension of the Ryu-Takayanagi (RT) formula\, in whi
ch extremal surfaces computing entanglement entropy are allowed to pass th
rough the brane into its dual geometry. This new rule reproduces the Page
curve for evaporating black holes\, consistently with the recently propose
d "island formula". We then separate the radiation system into pieces. Our
extended RT rule shows that the entanglement wedge of the union of radiat
ion subsystems covers the black hole interior at late times\, but the unio
n of entanglement wedges of the subsystems may not. This result points to
a secret sharing scheme in Hawking radiation wherein reconstruction of cer
tain regions in the interior is impossible with any subsystem of the radia
tion\, but possible with all of it.\n\n-----\n\n1) Please display your nam
e when you join the seminar.\n\n2) Your microphone is muted by default. Pl
ease only unmute it if you wish to make a question or comment\, and then m
ute it back again.\n\n------\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Kolchmeyer (Harvard)
DTSTART:20200708T130000Z
DTEND:20200708T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/9
DESCRIPTION:Title: Entanglement Entropy in Jackiw-Teitelboim Gravity\nby
David Kolchmeyer (Harvard) as part of GQFI-UGent-WST Seminars\n\n\nAbstra
ct\nI will explain how to use the quantum Ryu-Takayanagi formula to comput
e entanglement entropies in pure JT gravity\, including all of the perturb
ative graviton corrections. I will also explain why it is not possible to
factorize the gravity Hilbert space in a local way. The tension between de
fining a local and isometric factorization map motivates the insertion of
a "defect operator" into the standard definition of the Renyi entropy. The
defect operator has a clear interpretation in the Euclidean replica calcu
lation of the entropy. The contribution of the defect operator to the enta
nglement entropy matches the area term in the quantum Ryu-Takayanagi formu
la.\n\n-----\n\n1) Please display your name when you join the seminar.\n\n
2) Your microphone is muted by default. Please only unmute it if you wish
to make a question or comment\, and then mute it back again.\n\n------\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Edgar Shaghoulian (Cornell University)
DTSTART:20200715T130000Z
DTEND:20200715T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/10
DESCRIPTION:Title: Islands in asymptotically flat 2d gravity\nby Edgar
Shaghoulian (Cornell University) as part of GQFI-UGent-WST Seminars\n\n\nA
bstract\nAsymptotically flat two-dimensional dilaton gravity coupled to a
conformal field theory of large central charge provides a useful toy model
for semiclassical black holes and the information paradox. Analyses of th
e asymptotic information flux as given by the entanglement entropy show th
at it follows the Hawking curve\, indicating that information is destroyed
in these models. Recently\, motivated by developments in AdS/CFT\, a semi
classical island rule for entropy has been proposed. We define and compute
the island rule entropy for black hole formation and evaporation in the l
arge-N RST model of dilaton gravity and show that\, in contrast\, it follo
ws the unitary Page curve.\n\n1) Please display your name when you join th
e seminar.\n\n2) Your microphone is muted by default. Please only unmute i
t if you wish to make a question or comment\, and then mute it back again.
\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marius Gerbershagen (Wuerzburg University)
DTSTART:20200722T130000Z
DTEND:20200722T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/11
DESCRIPTION:Title: Complexity measures from geometric actions on Virasoro c
oadjoint orbits\nby Marius Gerbershagen (Wuerzburg University) as part
of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe explore connections between
computational complexity in CFTs\, geometric actions on coadjoint orbits o
f the Virasoro group and Liouville theory. Previously\, it was shown in [a
rXiv:1807.04422] that by choosing a suitable cost function\, the resulting
complexity functional is equivalent to a geometric action\, up to a term
that originates from the central extension. We show that this term can be
recovered by modifying the cost function\, making the equivalence exact. W
e then determine the optimal circuits for these complexity measures and ca
lculate the corresponding costs. We find that in most cases the complexity
only measures the cost associated to phase changes\, while assigning zero
cost to the non-phase changing part of the transformation. Furthermore\,
we briefly review how geometric actions arise from the gravity theory and
derive an equivalence between the sum of two geometric actions and Liouvil
le theory. From this equivalence statement\, we obtain a mapping of optima
l circuits from the path integral optimization approach and from our compl
exity proposal.\n\n1) Please display your name when you join the seminar.\
n\n2) Your microphone is muted by default. Please only unmute it if you wi
sh to make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mario Flory (Jagiellonian University)
DTSTART:20200909T130000Z
DTEND:20200909T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/12
DESCRIPTION:Title: Geometry of Complexity in CFT2\nby Mario Flory (Jagi
ellonian University) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\n"We
study circuit and state complexity in the universal setting of (1+1)-dime
nsional conformal field theory and unitary transformations generated by th
e stress-energy tensor. We provide a unified view of assigning a cost t
o circuits based on the Fubini-Study metric\, iteratively solve the emergi
ng integro-differential equation for sample optimal circuits and discus
s the sectional curvature of the underlying geometry. We also discuss the
relation of our work to Euler-Arnold type equations such as the Korteweg-d
e Vries and Hunter-Saxton equations."\n\n1) Please display your name when
you join the seminar.\n\n2) Your microphone is muted by default. Please on
ly unmute it if you wish to make a question or comment\, and then mute it
back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pedro Jorge Martinez (Universidad Nacional de La Plata)
DTSTART:20200916T130000Z
DTEND:20200916T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/13
DESCRIPTION:Title: Modular Hamiltonian for (holographic) excited states
\nby Pedro Jorge Martinez (Universidad Nacional de La Plata) as part of GQ
FI-UGent-WST Seminars\n\n\nAbstract\nWe study the Tomita-Takesaki construc
tion for a family of excited states that\, in a strongly coupled CFT - at
large N-\, correspond to coherent states in an asymptotically AdS spacetim
e geometry. We compute the modular flow and modular Hamiltonian associated
to these excited states in the Rindler wedge and for a ball shaped entang
ling surface. Using holography\, one can compute the bulk modular flow and
construct the Tomita-Takesaki theory for these cases. We also discuss gen
eralizations of the entanglement regions in the bulk and how to estimate t
he modular Hamiltonian in a large N approximation. Finally we present a ho
lographic formula\, based on the BDHM prescription\, to compute the modula
r evolution of operators in the corresponding CFT algebra.\n\n1) Please di
splay your name when you join the seminar.\n\n2) Your microphone is muted
by default. Please only unmute it if you wish to make a question or commen
t\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexey Milekhin
DTSTART:20200923T130000Z
DTEND:20200923T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/14
DESCRIPTION:Title: Humanly Traversable Wormholes\nby Alexey Milekhin as
part of GQFI-UGent-WST Seminars\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roberto Emparan (Universitat de Barcelona)
DTSTART:20200930T130000Z
DTEND:20200930T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/15
DESCRIPTION:Title: Quantum BTZ black hole\nby Roberto Emparan (Universi
tat de Barcelona) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI will
begin by reviewing the framework of braneworld holography as a means of s
tudying quantum effects on black holes including the gravitational backrea
ction of strongly-coupled conformal fields. Then I will describe a hologra
phic construction of quantum rotating BTZ black holes (quBTZ) using an exa
ct four-dimensional bulk solution. Besides yielding the quantum-corrected
geometry and the renormalized stress tensor of quBTZ\, we use it to show t
hat the quantum black hole entropy\, which includes the entanglement of th
e fields outside the horizon\, rather non-trivially satisfies the first la
w of thermodynamics\, while the Bekenstein-Hawking-Wald entropy does not.\
n\n1) Please display your name when you join the seminar.\n\n2) Your micro
phone is muted by default. Please only unmute it if you wish to make a que
stion or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandre Belin (CERN)
DTSTART:20201007T130000Z
DTEND:20201007T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/16
DESCRIPTION:Title: Gravitational path integral from the T^2 deformation
\nby Alexandre Belin (CERN) as part of GQFI-UGent-WST Seminars\n\n\nAbstra
ct\nI will describe the $T^2$ deformation of large $N$ conformal field the
ories\, a higher dimensional generalization of the $TT$-deformation. The d
eformed partition function satisfies a flow equation of the diffusion type
. I will explain how to solve this equation by finding its diffusion kerne
l\, which is given by the Euclidean gravitational path integral in $d+1$ d
imensions between two boundaries with Dirichlet boundary conditions for th
e metric. An interesting output of the flow equation is the gravitational
path integral measure which is consistent with a constrained phase space q
uantization. Finally\, I will comment on the relation between the radial w
ave function and the Hartle-Hawking wave functions dual to states in the C
FT\, and propose a way of obtaining the volume of the maximal slice from t
he $T^2$ deformation.\n\n1) Please display your name when you join the sem
inar.\n\n2) Your microphone is muted by default. Please only unmute it if
you wish to make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Horacio Casini (Centro Atomico Bariloche)
DTSTART:20201014T130000Z
DTEND:20201014T143000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/17
DESCRIPTION:Title: Entropic order parameters for the phases of QFT\nby
Horacio Casini (Centro Atomico Bariloche) as part of GQFI-UGent-WST Semina
rs\n\n\nAbstract\nWe propose entropic order parameters that capture the ph
ysics of generalized symmetries and phases in QFT's. We do so by an analys
is of simple properties (additivity and Haag duality) of the net of operat
or algebras attached to space-time regions. We observe that different type
s of symmetries are associated with the breaking of these properties in re
gions of different non-trivial topologies. When such topologies are connec
ted\, we show the non locally generated operators generate an Abelian symm
etry group\, and their commutation relations are fixed. The existence of o
rder parameters with area law\, like the Wilson loop for the confinement p
hase\, or the 't Hooft loop for the dual Higgs phase\, is shown to imply t
he existence of more than one possible choice of algebras for the same und
erlying theory. A natural entropic order parameter arises by this non-uniq
ueness. We display aspects of the phases of theories with generalized symm
etries in terms of these entropic order parameters. In particular\, the co
nnection between constant and area laws for dual order and disorder parame
ters is transparent in this approach\, new constraints arising from confor
mal symmetry are revealed\, and the algebraic origin of the Dirac quantiza
tion condition (and generalizations thereof) is described. A novel tool in
this approach is the entropic certainty relation satisfied by the dual re
lative entropies associated with complementary regions\, which quantitativ
ely relates the statistics of order and disorder parameters.\n\n1) Please
display your name when you join the seminar.\n\n2) Your microphone is mute
d by default. Please only unmute it if you wish to make a question or comm
ent\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jorrit Kruthoff (Stanford)
DTSTART:20201021T150000Z
DTEND:20201021T163000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/18
DESCRIPTION:Title: Bootstrapping Matrix Quantum Mechanics\nby Jorrit Kr
uthoff (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nLarge
N matrix quantum mechanics is central to holographic duality but not solva
ble in the most interesting cases. We show that the spectrum and simple ex
pectation values in these theories can be obtained numerically via a boots
trap methodology. In this approach\, operator expectation values are relat
ed by symmetries\, such as time translation and SU(N) gauge invariance\, a
nd then bounded with certain positivity constraints. We first demonstrate
how this method efficiently solves the conventional quantum anharmonic osc
illator. We then reproduce the known solution of large N single matrix qua
ntum mechanics. Finally\, we present new results on the ground state of la
rge N two matrix quantum mechanics.\n\n1) Please display your name when yo
u join the seminar.\n\n2) Your microphone is muted by default. Please only
unmute it if you wish to make a question or comment\, and then mute it ba
ck again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hugo Camargo (AEI Potsdam)
DTSTART:20201112T140000Z
DTEND:20201112T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/19
DESCRIPTION:by Hugo Camargo (AEI Potsdam) as part of GQFI-UGent-WST Semina
rs\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alice Di Tucci (AEI Potsdam)
DTSTART:20201104T140000Z
DTEND:20201104T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/20
DESCRIPTION:Title: Lessons for quantum cosmology from anti-de Sitter black
holes\nby Alice Di Tucci (AEI Potsdam) as part of GQFI-UGent-WST Semin
ars\n\n\nAbstract\nIn this talk I will discuss gravitational path integral
s in the presence of negative and positive cosmological constant within th
e minisuperspace approximation\, putting special emphasis on boundary cond
itions and integration contours. I will show how the Hawking-Page transiti
on is recovered in this setting. These findings have direct consequences f
or the no-boundary proposal in cosmology\, because the anti–de Sitter ca
lculation can be brought into one-to-one correspondence with a path integr
al for de Sitter space with Neumann conditions imposed at the nucleation o
f the Universe.\n\n1) Please display your name when you join the seminar.\
n\n2) Your microphone is muted by default. Please only unmute it if you wi
sh to make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Victor Gorbenko (Stanford)
DTSTART:20201111T160000Z
DTEND:20201111T173000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/21
DESCRIPTION:Title: Bra-ket wormholes in gravitationally prepared states
\nby Victor Gorbenko (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAb
stract\nWe consider two dimensional CFT states that are produced by a grav
itational path integral. As a first case\, we consider a state produced by
Euclidean AdS$_2$ evolution followed by flat space evolution. We use the
fine grained entropy formula to explore the nature of the state. We find t
hat the naive hyperbolic space geometry leads to a paradox. This is solved
if we include a geometry that connects the bra with the ket\, a bra-ket w
ormhole. The semiclassical Lorentzian interpretation leads to CFT state en
tangled with an expanding and collapsing Friedmann cosmology. As a second
case\, we consider a state produced by Lorentzian dS$_2$ evolution\, again
followed by flat space evolution. The most naive geometry also leads to a
similar paradox. We explore several possible bra-ket wormholes. The most
obvious one leads to a badly divergent temperature. The most promising one
also leads to a divergent temperature but by making a projection onto low
energy states we find that it has features that look similar to the previ
ous Euclidean case. In particular\, the maximum entropy of an interval in
the future is set by the de Sitter entropy.\n\n1) Please display your name
when you join the seminar.\n\n2) Your microphone is muted by default. Ple
ase only unmute it if you wish to make a question or comment\, and then mu
te it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marina Huerta (Centro Atomico Bariloche)
DTSTART:20201125T140000Z
DTEND:20201125T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/22
DESCRIPTION:Title: Entanglement\, Global Symmetries and Topological contrib
utions\nby Marina Huerta (Centro Atomico Bariloche) as part of GQFI-UG
ent-WST Seminars\n\n\nAbstract\nRecently it was shown that Entanglement En
tropy for theories based on algebras of operators invariant under a global
symmetry is non uniquely defined. This is a direct consequence of the fac
t that the algebra assigned to the region\, in case of regions with non-tr
ivial topology\, does not satisfy the expected property of additivity/dual
ity. This can be understood by noticing the existence of operators which c
annot be locally generated within the region. These are called twists and
intertwiners belonging to the region or its complement respectively. In th
is scenario\, novel universal contributions\, topological in nature\, aris
e.\n\n1) Please display your name when you join the seminar.\n\n2) Your mi
crophone is muted by default. Please only unmute it if you wish to make a
question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiao-Liang Qi (Stanford)
DTSTART:20201216T160000Z
DTEND:20201216T173000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/23
DESCRIPTION:Title: Effective entropy of quantum fields coupled with gravity
\nby Xiao-Liang Qi (Stanford) as part of GQFI-UGent-WST Seminars\n\n\n
Abstract\nEntanglement entropy quantifies the amount of uncertainty of a q
uantum state. For quantum fields in curved space\, entanglement entropy of
the quantum field theory degrees of freedom is well-defined for a fixed b
ackground geometry. In this paper\, we propose a generalization of the qua
ntum field theory entanglement entropy by including dynamical gravity. The
generalized quantity named effective entropy\, and its Renyi entropy gene
ralizations\, are defined by analytic continuation of a gravitational path
integral on replica geometry with a co-dimension-2 brane at the boundary
of region we are studying. We discuss different approaches to define the r
egion in a gauge invariant way\, and show that the effective entropy satis
fies the quantum extremal surface formula. When the quantum fields carry a
significant amount of entanglement\, the quantum extremal surface can hav
e a topology transition\, after which an entanglement island region appear
s. Our result generalizes the Hubeny-Rangamani-Takayanagi formula of holog
raphic entropy (with quantum corrections) to general geometries without as
ymptotic AdS boundary\, and provides a more solid framework for addressing
problems such as the Page curve of evaporating black holes in asymptotic
flat spacetime. We apply the formula to two example systems\, a closed two
-dimensional universe and a four-dimensional maximally extended Schwarzchi
ld black hole. We discuss the analog of the effective entropy in random te
nsor network models\, which provides more concrete understanding of quantu
m information properties in general dynamical geometries. By introducing a
ncilla systems\, we show how quantum information in the entanglement islan
d can be reconstructed in a state-dependent and observer-dependent map. We
study the closed universe (without spatial boundary) case and discuss how
it is related to open universe.\n\n1) Please display your name when you j
oin the seminar.\n\n2) Your microphone is muted by default. Please only un
mute it if you wish to make a question or comment\, and then mute it back
again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jamie Sully (University of British Columbia)
DTSTART:20210120T150000Z
DTEND:20210120T160000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/24
DESCRIPTION:Title: Sharp Holography for Boundary Conformal Field theory
\nby Jamie Sully (University of British Columbia) as part of GQFI-UGent-WS
T Seminars\n\n\nAbstract\nOver the last decade we have learned a great dea
l about the conditions that allow a conformal field theory to have an effe
ctive description in terms of semiclassical gravity. But what about when w
e add defects or boundaries to the CFT? Under what conditions can we expec
t those too to be described by gravity plus semiclassical branes? By exami
ning holographic phase transitions in entanglement entropy\, I will show t
hat the possible operator spectrum of BCFTs is constrained by agreement wi
th the gravitational dual. And using techniques from the boundary bootstra
p\, I will argue that even well-behaved holographic CFTs almost never have
a good bulk dual once we add a boundary.\n\n1) Please display your name w
hen you join the seminar.\n \n2) Your microphone is muted by default. Plea
se only unmute it if you wish to make a question or comment\, and then mut
e it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johanna Erdmenger (University of Würzburg)
DTSTART:20210127T140000Z
DTEND:20210127T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/25
DESCRIPTION:Title: New materials for holographic hydrodynamics\nby Joha
nna Erdmenger (University of Würzburg) as part of GQFI-UGent-WST Seminars
\n\n\nAbstract\nMy talk will be devoted to an interdisciplinary project in
volving both holographers and condensed matter physicists. So far\, graphe
ne is the material of choice for experimentally realizing hydrodynamic beh
aviour of strongly coupled electrons in a solid. However\, in graphene the
electron-electron coupling is only of order one in suitable units\, still
far away from the infinite coupling limit studied in holographic hydrodyn
amics. Here we propose a new Dirac material\, Scandium-substituted Herbert
smithite\, in which the electron-electron coupling is enhanced by a factor
3.2 as compared to graphene. Using a holographic approach that involves f
inite-coupling higher-curvature corrections to the famous holographic resu
lt of 1/4 pi for the ratio of shear viscosity over entropy density (eta/s)
\, we estimate eta/s in the coupling regime of the proposed new material.
The associated range of Reynolds numbers even puts turbulent behaviour wit
hin reach. In the talk I will give an introduction to the condensed matter
aspects of the project and present the holographic computations.\n\nBased
on 1911.06810 (Nature Communications 11 3997 (2020))\n\n----- 1) Please d
isplay your name when you join the seminar. 2) Your microphone is muted by
default. Please only unmute it if you wish to make a question or comment\
, and then mute it back again. ------\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joshua Kirklin (Okinawa Institute of Science and Technology)
DTSTART:20210210T140000Z
DTEND:20210210T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/26
DESCRIPTION:Title: Uhlmann Phase\, Black Hole Information and Holography\nby Joshua Kirklin (Okinawa Institute of Science and Technology) as part
of GQFI-UGent-WST Seminars\n\n\nAbstract\nIn the 1980s\, Armin Uhlmann de
scribed a natural generalisation of Berry phase to mixed states which has
come to be known as Uhlmann phase. I will describe a series of recent resu
lts characterising the Uhlmann phase of subsystems in quantum gravity. Fir
st\, assuming replica wormholes contribute to the path integral\, I will s
how that measurements of the Uhlmann phase of Hawking radiation allows one
to reconstruct the phase space of the interior of a black hole (past the
Page time)\, providing a protocol for the recovery of all infalling classi
cal information. This is a generalisation of a previous result concerning
entanglement wedges in holography. Next\, I describe a path integral formu
la for the Uhlmann phase of a generic highly entangled system\, explaining
how it appears to inevitably involve an extra dimension generated by modu
lar flow\, despite a lack of any holographic assumptions. Finally\, I comm
ent on the operational meaning of Uhlmann phase\, and how it's significanc
e may relate to decoherence.\n\n1) Please display your name when you join
the seminar.\n \n2) Your microphone is muted by default. Please only unmut
e it if you wish to make a question or comment\, and then mute it back aga
in.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean-Luc Lehners (AEI Potsdam)
DTSTART:20210217T140000Z
DTEND:20210217T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/27
DESCRIPTION:Title: Circuit complexity of primordial perturbations\nby J
ean-Luc Lehners (AEI Potsdam) as part of GQFI-UGent-WST Seminars\n\n\nAbst
ract\nI will discuss the quantum circuit complexity of cosmological pertur
bations in different models of the early universe. A natural measure for t
he complexity of cosmological perturbations is based on the symplectic gro
up\, allowing us to identify complexity with geodesics in the hyperbolic p
lane. We investigate the complexity of both the mode functions and the phy
sical perturbations\, arguing that the latter often provides a more insigh
tful description of the physics involved. In all models the total complexi
ty reached is rather large. Inflationary perturbations may be represented
by a comparatively simple quantum circuit\, while the perturbations during
a matter-dominated contracting phase present the most rapid growth in com
plexity. Ekpyrotic perturbations reside in the middle and are distinguishe
d by the smallest growth of complexity before horizon exit. Our analysis s
erves to highlight how different cosmological models achieve the same end
result for the perturbations via different routes and how all models show
a pronounced sensitivity to initial conditions.\n\n1) Please display your
name when you join the seminar.\n \n2) Your microphone is muted by default
. Please only unmute it if you wish to make a question or comment\, and th
en mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giuseppe Policastro (École Normale Supérieure)
DTSTART:20210224T140000Z
DTEND:20210224T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/28
DESCRIPTION:Title: Transport in TTbar-deformed conformal field theories
\nby Giuseppe Policastro (École Normale Supérieure) as part of GQFI-UGen
t-WST Seminars\n\n\nAbstract\nI will discuss out of equilibrium properties
of conformal field theories deformed by the TTbar deformation. Such theor
ies are very interesting because they can describe the effect of an irrele
vant perturbation of a critical system\, and they are exactly solvable\, t
o some extent. They can be approached from two different point of views: u
sing integrability techniques and the holographic correspondence. I will f
ocus on the energy and momentum Drude weights and diffusion constants\, as
well as the non equilibrium steady states which emerge after an inhomogen
eous quench. The transport coefficients and non equilibrium steady state c
urrent admit closed form expressions\, whose universality is established b
y the agreement of the two approaches. I will finally discuss the prospect
s of further extensions of our results.\n\n1) Please display your name whe
n you join the seminar.\n \n2) Your microphone is muted by default. Please
only unmute it if you wish to make a question or comment\, and then mute
it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dongsheng Ge (University of Warsaw)
DTSTART:20210303T140000Z
DTEND:20210303T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/29
DESCRIPTION:Title: Energy reflection and transmission at 2D holographic int
erfaces\nby Dongsheng Ge (University of Warsaw) as part of GQFI-UGent-
WST Seminars\n\n\nAbstract\nScattering from conformal interfaces in two di
mensions is universal in that the flux of reflected and transmitted energy
does not depend on the details of the initial state. In this talk\, we pr
esent the first gravitational calculation of energy reflection and transmi
ssion coefficients for interfaces with thin-brane holographic duals. Our r
esult for the reflection coefficient depends monotonically on the tension
of the dual string anchored at the interface\, and obeys the lower bound r
ecently derived from the ANEC in conformal field theory. The B(oundary)CFT
limit is recovered for infinite ratio of the central charges.\n\n1) Pleas
e display your name when you join the seminar.\n \n2) Your microphone is m
uted by default. Please only unmute it if you wish to make a question or c
omment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ivan Munoz (Pontificia Universidad Catolica de Chile)
DTSTART:20210317T140000Z
DTEND:20210317T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/30
DESCRIPTION:Title: Loops in Holographic Correlators\nby Ivan Munoz (Pon
tificia Universidad Catolica de Chile) as part of GQFI-UGent-WST Seminars\
n\n\nAbstract\nIn the early days of AdS/CFT correspondence\, it was alread
y clear how to compute CFT correlators from the AdS side. Working at tree
level in the bulk\, and renormalizing the IR divergence properly due to th
e infinite volume of AdS\, it is obtained the correct conformal correlator
. We extend this treatment considering quantum corrections to the fields i
n the AdS and compute the holographic correlation function with loops in t
he bulk and study the role of IR divergences.\n\n1) Please display your na
me when you join the seminar.\n \n2) Your microphone is muted by default.
Please only unmute it if you wish to make a question or comment\, and then
mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ignacio Reyes (AEI Potsdam)
DTSTART:20210324T140000Z
DTEND:20210324T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/31
DESCRIPTION:Title: Moving mirrors\, Page curves and bulk entropies in AdS2<
/a>\nby Ignacio Reyes (AEI Potsdam) as part of GQFI-UGent-WST Seminars\n\n
\nAbstract\nUnderstanding the entanglement of radiation in QFT has been a
long standing challenge\, with implications from black hole thermodynamics
to quantum information. We demonstrate how the free fermion in 1+1-dimens
ions reveals the details of the density matrix of the radiation produced b
y a moving mirror. Using the resolvent method rather than standard boundar
y CFT techniques we derive the Renyi entropies\, modular Hamiltonian and f
low of the radiation\, and determine when mirrors generate unitary transfo
rmations. Exploring the Renyi entropies on AdS2 with reflecting boundary c
onditions yields surprising consequences for quantum extremal surfaces in
JT gravity.\n\n1) Please display your name when you join the seminar.\n \n
2) Your microphone is muted by default. Please only unmute it if you wish
to make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan de Boer (University of Amsterdam)
DTSTART:20210331T130000Z
DTEND:20210331T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/32
DESCRIPTION:Title: The OPE Randomness Hypothesis\, Euclidean Wormholes\, an
d Effective Field Theory\nby Jan de Boer (University of Amsterdam) as
part of GQFI-UGent-WST Seminars\n\n\nAbstract\nRecent developments in holo
graphy indicate that the semi-classical Euclidean path-integral of Einstei
n gravity is much more powerful than previously anticipated. It is capable
of reproducing a unitary Page curve for black hole evaporation\, and can
even capture some features of the discrete nature of black hole microstate
s. Wormhole geometries play a key role in this context. I will propose a m
echanism to explain this in the CFT: the OPE Randomness Hypothesis. This a
nsatz is a generalization of the Eigenstate Thermalization Hypothesis whic
h applies to chaotic CFTs\, and treats OPE coefficients of heavy operators
as random variables with a given probability distribution. I will present
two applications of this framework: First\, it resolves a factorization p
uzzle in AdS_3/CFT_2 due to the genus-2 wormhole\, as raised by Maoz and M
aldacena. Second\, it provides an argument against global symmetries in qu
antum gravity. Based on arXiv:2006.05499 and arXiv:2012.07875.\n\n1) Plea
se display your name when you join the seminar.\n \n2) Your microphone is
muted by default. Please only unmute it if you wish to make a question or
comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Arjun Kar (University of British Columbia)
DTSTART:20210421T150000Z
DTEND:20210421T160000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/33
DESCRIPTION:Title: A hierarchy of complexity growth from integrability and
chaos\nby Arjun Kar (University of British Columbia) as part of GQFI-U
Gent-WST Seminars\n\n\nAbstract\nQuantum complexity has been conjectured t
o be relevant for black hole interiors. In particular\, Susskind has con
jectured a generic form of complexity growth and saturation for maximally
chaotic systems like black holes. Using geodesic complexity techniques\,
we study the complexity of time evolution in free\, integrable\, and chao
tic systems with N degrees of freedom. We demonstrate that the growth ra
te of this complexity is related to more familiar properties of physical t
heories like 1) the existence of creation/annihilation operators and 2) sm
eared thermal two-point functions. Using these properties\, we find that
the complexity saturates in free\, integrable\, and chaotic theories at t
ime scales which are on the order of N^{1/2}\, polynomial in N\, and expon
ential in N\, respectively. Our results in the free theory improve an ex
isting bound in the complexity theory literature\, and our results in chao
tic theories are based only on coarse properties of the spectrum and eigen
states.\n\n1) Please display your name when you join the seminar.\n \n2) Y
our microphone is muted by default. Please only unmute it if you wish to m
ake a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthew Dodelson (Tokyo U.\, IPMU)
DTSTART:20210428T130000Z
DTEND:20210428T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/34
DESCRIPTION:Title: Singularities of thermal correlators at strong coupling<
/a>\nby Matthew Dodelson (Tokyo U.\, IPMU) as part of GQFI-UGent-WST Semin
ars\n\n\nAbstract\nI will describe work with Ooguri on the singularities o
f the two point function at finite temperature in a conformal field theory
in more than two dimensions. At weak coupling the only singularity is on
the light cone\, but in the large N\, large lambda regime a new singularit
y emerges. This new singularity corresponds to a null geodesic in the AdS/
Schwarzschild black hole\, which may wrap the photon sphere many times. Af
ter deriving this result\, I will discuss the resolution of these singula
rities by stringy tidal effects at finite lambda. The basic tool I will us
e is to take the Penrose limit around a given null geodesic\, and then use
the solubility of the string theory in this background. I will also discu
ss applications to rotating black holes.\n\n1) Please display your name wh
en you join the seminar. 2) Your microphone is muted by default. Please on
ly unmute it if you wish to make a question or comment\, and then mute it
back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dionysios Anninos (King's College London)
DTSTART:20210505T130000Z
DTEND:20210505T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/35
DESCRIPTION:Title: Toward an infrared realisation of dS in AdS?\nby Dio
nysios Anninos (King's College London) as part of GQFI-UGent-WST Seminars\
n\n\nAbstract\nWe explore the possibility of realising a portion of a two-
dimensional de Sitter world in an asymptotically anti-de Sitter universe.
We consider the question from both a macroscopic and microscopic perspecti
ve.\n\n1) Please display your name when you join the seminar. 2) Your micr
ophone is muted by default. Please only unmute it if you wish to make a qu
estion or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jose Barbon (IFT-UAM/CSIC)
DTSTART:20210519T130000Z
DTEND:20210519T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/36
DESCRIPTION:Title: The complexity of gravitational clumping\nby Jose Ba
rbon (IFT-UAM/CSIC) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWith
in the holographic Complexity=Volume proposal\, we study correspondences b
etween the rate of complexity growth and the degree of gravitational clump
ing in the bulk\, quantified as an average infall momentum. We show that s
uch a connection is largely implicit in the CV proposal through the moment
um constraint of GR. We discuss generalisations of these momentum/complexi
ty relations\, as well as some topological obstructions. (Work in collabor
ation with J. Martin-Garcia and M. Sasieta).\n\n1) Please display your nam
e when you join the seminar.\n \n2) Your microphone is muted by default. P
lease only unmute it if you wish to make a question or comment\, and then
mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Erik Tonni (SISSA\, INFN)
DTSTART:20210526T130000Z
DTEND:20210526T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/37
DESCRIPTION:Title: Modular Hamiltonians for the massless Dirac field in the
presence of a boundary or of a defect\nby Erik Tonni (SISSA\, INFN) a
s part of GQFI-UGent-WST Seminars\n\n\nAbstract\nThe reduced density matri
x of a spatial subsystem can be written as the exponential of the modular
Hamiltonian\, hence this operator contains a lot of information about the
entanglement of the corresponding spatial bipartition. First we consider t
he massless Dirac field on the half-line\, imposing the most general bound
ary conditions that ensure the global energy conservation. This leads to t
wo inequivalent phases where either the vector or the axial symmetry is pr
eserved. In these two phases\, we discuss the analytic expressions for the
modular Hamiltonians of an interval on the half-line when the system is i
n its ground state\, for the corresponding modular flows of the Dirac fiel
d and for the corresponding modular correlators. The method allows to obta
in analytic expressions also for the modular Hamiltonians\, the modular fl
ows and the modular correlators for two disjoint equal intervals at the sa
me distance from a point-like defect characterised by a unitary scatterin
g matrix\, that allows both reflection and transmission.\n\n1) Please disp
lay your name when you join the seminar.\n \n2) Your microphone is muted b
y default. Please only unmute it if you wish to make a question or comment
\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Onkar Parrikar (Stanford)
DTSTART:20210602T130000Z
DTEND:20210602T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/38
DESCRIPTION:Title: Building tensor networks for holographic states\nby
Onkar Parrikar (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAbstract
\nWe discuss a one-parameter family of states in two-dimensional holograph
ic conformal field theories which are constructed via the Euclidean path i
ntegral of an effective theory on a family of hyperbolic slices in the dua
l bulk geometry. The effective theory in question is the CFT flowed under
a TT* deformation\, which "folds" the boundary CFT towards the bulk time
-reflection symmetric slice. We propose that these novel Euclidean path in
tegral states in the CFT can be interpreted as continuous tensor network (
CTN) states. We argue that these CTN states satisfy a Ryu-Takayanagi-like
minimal area upper bound on the entanglement entropies of boundary interva
ls\, with the coefficient being equal to 1/4G_N\; the CTN corresponding t
o the bulk time-reflection symmetric slice saturates this bound.\n\n1) Ple
ase display your name when you join the seminar.\n \n2) Your microphone is
muted by default. Please only unmute it if you wish to make a question or
comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Irene Valenzuela (Harvard)
DTSTART:20210609T140000Z
DTEND:20210609T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/39
DESCRIPTION:Title: A CFT Distance Conjecture\nby Irene Valenzuela (Harv
ard) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe formulate a seri
es of conjectures relating the geometry of conformal manifolds to the spec
trum of local operators in conformal field theories in d>2 spacetime dimen
sions. We focus on conformal manifolds with limiting points at infinite di
stance with respect to the Zamolodchikov metric. Our central conjecture is
that all theories at infinite distance possess an emergent higher-spin sy
mmetry\, generated by an infinite tower of currents whose anomalous dimens
ions vanish exponentially in the distance. Stated geometrically\, the diam
eter of a non-compact conformal manifold must diverge logarithmically in t
he higher-spin gap. In the holographic context our conjectures are related
to the Distance Conjecture in the swampland program. Interpreted gravitat
ionally\, they imply that approaching infinite distance in moduli space at
fixed AdS radius\, a tower of higher-spin fields becomes massless at an e
xponential rate that is bounded from below in Planck units. We discuss fur
ther implications for conformal manifolds of superconformal field theories
in three and four dimensions.\n\n1) Please display your name when you joi
n the seminar.\n\n\n2) Your microphone is muted by default. Please only un
mute it if you wish to make a question or comment\, and then mute it back
again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Janet Hung (Fudan University)
DTSTART:20210616T130000Z
DTEND:20210616T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/40
DESCRIPTION:Title: padic tensor network and emergent Einstein equation\
nby Janet Hung (Fudan University) as part of GQFI-UGent-WST Seminars\n\n\n
Abstract\nWe take the tensor network describing explicit p-adic CFT partit
ion functions proposed in 1902.01411\, and consider boundary conditions of
the network describing a deformed Bruhat-Tits (BT) tree geometry. We demo
nstrate that this geometry satisfies an emergent graph Einstein equation i
n a unique way that is consistent with the bulk effective matter action en
coding the same correlation function as the tensor network\, at least in t
he perturbative limit order by order away from the pure BT tree. Moreover\
, the (perturbative) definition of the graph curvature in the Mathematics
literature naturally emerges from the consistency requirements of the emer
gent Einstein equation. This could provide new insights into the understan
ding of gravitational dynamics potentially encoded in more general tensor
networks.\n\n1) Please display your name when you join the seminar.\n \n2)
Your microphone is muted by default. Please only unmute it if you wish to
make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dominik Neuenfeld (Perimeter Institute)
DTSTART:20211005T130000Z
DTEND:20211005T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/41
DESCRIPTION:Title: Holonomy Constraints in Double Holography\nby Domini
k Neuenfeld (Perimeter Institute) as part of GQFI-UGent-WST Seminars\n\n\n
Abstract\nI discuss the relation between the d-dimensional BCFT and CFT+gr
avity descriptions of double holography. In both descriptions entropies ca
n be computed using the RT formula in a (d+1)-dimensional bulk. However\,
I argue that the standard assumptions about entanglement wedge reconstruct
ion suggest that the homology condition for RT surfaces depends on which o
f the "boundary" formulations is taken. After discussing implications for
the relation between von Neumann entropy and the entropy computed using th
e island formula\, I will show how the island formula arises in a simple q
ubit model. Based on those results I speculate about the emergence of semi
-classical gravity from quantum gravity.\n\n1) Please display your name wh
en you join the seminar.\n\n2) Your microphone is muted by default. Please
only unmute it if you wish to make a question or comment\, and then mute
it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mark Mezei (SCGP\, Stony Brook)
DTSTART:20211019T130000Z
DTEND:20211019T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/42
DESCRIPTION:Title: The volume of the black hole interior at late times\
nby Mark Mezei (SCGP\, Stony Brook) as part of GQFI-UGent-WST Seminars\n\n
\nAbstract\nUnderstanding the fate of semi-classical black hole solutions
at very late times is one of the most important open questions in quantum
gravity. In this talk\, we provide a path integral definition of the volum
e of the black hole interior and study it at arbitrarily late times for bl
ack holes in various models of two-dimensional gravity. Because of a novel
universal cancellation between the contributions of the semi-classical bl
ack hole spectrum and some of its non-perturbative corrections\, we find t
hat\, after a linear growth at early times\, the length of the interior sa
turates at a time\, and towards a value\, that is exponentially large in t
he entropy of the black hole. This provides a non-perturbative confirmatio
n of the complexity equals volume proposal since complexity is also expect
ed to plateau at the same value and at the same time.\n\n1) Please display
your name when you join the seminar.\n\n2) Your microphone is muted by de
fault. Please only unmute it if you wish to make a question or comment\, a
nd then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luca Delacretaz (University of Chicago)
DTSTART:20211026T130000Z
DTEND:20211026T140000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/43
DESCRIPTION:Title: Thermal aspects of 2d QFTs\nby Luca Delacretaz (Univ
ersity of Chicago) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI wil
l present general constraints on (1+1)d QFTs obtained by imposing causalit
y in the thermal state. One immediate consequence is the existence of a th
ermodynamic C-function\, providing an alternative proof to Zamolodchikov's
C-theorem. Similar considerations fix the sign of the TT-bar correction i
n non-integrable EFTs. Causality also severely constrains the out-of-equil
ibrium dynamics\, by placing a strong lower bound on the local equilibrati
on time beyond which hydrodynamics emerges as an effective description. Th
is establishes the conjectured "Planckian bound" on thermalization in the
context of (1+1)d QFTs.\n\nBased on: arXiv:2105.02229 [hep-th].\n\n1) Plea
se display your name when you join the seminar.\n\n2) Your microphone is m
uted by default. Please only unmute it if you wish to make a question or c
omment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tatsuma Nishioka (Yukawa Institute for Theoretical Physics)
DTSTART:20211102T140000Z
DTEND:20211102T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/44
DESCRIPTION:Title: Topological pseudo entropy\nby Tatsuma Nishioka (Yuk
awa Institute for Theoretical Physics) as part of GQFI-UGent-WST Seminars\
n\n\nAbstract\nRecently\, a new quantum information measure called pseudo
entropy was introduced as a generalization of entanglement entropy to quan
tify quantum correlation between initial and final states in a time-depend
ent system. In this talk\, I will examine some aspects of pseudo entropy i
n topological field theory and conformal field theory (CFT). In three-dime
nsional Chern-Simons theory\, pseudo entropy can be given by a partition f
unction on a three-sphere with Wilson loops in a similar manner to topolog
ical entanglement entropy. I will also show that the pseudo entropy in a c
ertain setup is equivalent to the interface entropy in two-dimensional CFT
s\, and leverage the equivalence to calculate the pseudo entropies in part
icular examples. Furthermore\, I will define a pseudo entropy extension of
the left-right entanglement entropy in two-dimensional boundary CFTs and
derive a universal formula for a pair of arbitrary boundary states.\n\n1)
Please display your name when you join the seminar.\n\n2) Your microphone
is muted by default. Please only unmute it if you wish to make a question
or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Olga Papadoulaki (Perimeter Institute)
DTSTART:20211109T140000Z
DTEND:20211109T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/45
DESCRIPTION:Title: Holography from the Wheeler-DeWitt equation\nby Olga
Papadoulaki (Perimeter Institute) as part of GQFI-UGent-WST Seminars\n\n\
nAbstract\nIn a theory of quantum gravity\, states can be represented as w
avefunctionals that assign an amplitude to a given configuration of matter
fields and the metric on a spatial slice. These wavefunctionals must obey
a set of constraints as a consequence of the diffeomorphism invariance of
the theory\, the most important of which is known as the Wheeler-DeWitt e
quation. I will present how to study these constraints perturbatively by e
xpanding them to leading nontrivial order in Newton’s constant about a b
ackground AdS spacetime. It will become clear that in perturbation theory\
, any wavefunctional that solves these constraints must have specific corr
elations between a component of the metric at infinity and energetic excit
ations of matter fields or transverse-traceless gravitons. These correlati
ons disallow strictly localized excitations. I will prove perturbatively t
hat two states or two density matrices that coincide at the boundary for a
n infinitesimal interval of time must coincide everywhere in the bulk. Thi
s analysis establishes a perturbative version of holography for theories o
f gravity coupled to matter in AdS.\n\n1) Please display your name when yo
u join the seminar.\n\n2) Your microphone is muted by default. Please only
unmute it if you wish to make a question or comment\, and then mute it ba
ck again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Felix Haehl (IAS)
DTSTART:20211116T140000Z
DTEND:20211116T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/46
DESCRIPTION:Title: Spin glasses and holography\nby Felix Haehl (IAS) as
part of GQFI-UGent-WST Seminars\n\n\nAbstract\nThe connections between di
sordered quantum systems (specifically the SYK model)\, ensemble averaging
\, and two-dimensional dilaton gravity underlie much of the recent progres
s on holography and quantum gravity. While the SYK model is a 'spin liquid
' even at low temperatures\, closely related disordered systems exhibit a
'spin glass' phase\, characterized by ergodicity breaking and slow dynamic
s. I will discuss simple spin glass models and some of their properties th
at are of interest from a gravitational point of view (such as thermodynam
ics and quantum chaos). I will propose a holographic interpretation of som
e crucial features that relates to the fragmentation instability of AdS2 t
owards a geometry with multiple throats. Based on work with Tarek Anous\,
Maine Christos\, and Subir Sachdev.\n\n1) Please display your name when yo
u join the seminar.\n\n2) Your microphone is muted by default. Please only
unmute it if you wish to make a question or comment\, and then mute it ba
ck again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nissan Itzhaki (Tel Aviv University)
DTSTART:20211123T140000Z
DTEND:20211123T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/47
DESCRIPTION:Title: Stringy Information and Black Holes\nby Nissan Itzha
ki (Tel Aviv University) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\
nWe show that in string theory\, due to non perturbative effects\, there a
re cases in which two states that semi classically are completely differen
t\, are in fact the same. One state cannot be excited without exciting the
other: they are two components of the same state in the exact theory. As
a result\, in some situations that include black holes\, the nature of inf
ormation in string theory is dramatically different than in field theory.
In particular\, each general relativity state\, that lives in the atmosphe
re of black fivebranes\, is accompanied by an excitation that lives on fol
ded strings\, which fill the black hole interior. This is likely related t
o the way that information is extracted from black holes in string theory\
, and we refer to it as stringy information.\n\n1) Please display your nam
e when you join the seminar.\n\n2) Your microphone is muted by default. Pl
ease only unmute it if you wish to make a question or comment\, and then m
ute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brian Swingle (Maryland University)
DTSTART:20211130T140000Z
DTEND:20211130T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/48
DESCRIPTION:Title: Effective Field Theory of Chaotic Spectral Correlations<
/a>\nby Brian Swingle (Maryland University) as part of GQFI-UGent-WST Semi
nars\n\n\nAbstract\nEnsembles of quantum chaotic systems are expected to e
xhibit random matrix universality in their energy spectrum. The presence o
f this universality can be diagnosed by looking for a linear in time 'ramp
' in the spectral form factor\, but for realistic systems this feature is
typically only visible after a sufficiently long time. Given the wide prev
alence of this random matrix behavior\, it is natural to ask for an effect
ive field theory which predicts the ramp and computes corrections to it ar
ising from physical constraints. I will present such an effective theory b
ased on fluctuating hydrodynamics. The theory can also be adapted to descr
ibe the effects of spontaneous symmetry breaking on spectral correlations.
\n\n1) Please display your name when you join the seminar.\n\n2) Your micr
ophone is muted by default. Please only unmute it if you wish to make a qu
estion or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Juan Pedraza (ICC Barcelona)
DTSTART:20211214T140000Z
DTEND:20211214T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/49
DESCRIPTION:Title: Lorentzian Threads and Holographic Complexity\nby Ju
an Pedraza (ICC Barcelona) as part of GQFI-UGent-WST Seminars\n\n\nAbstrac
t\nThe continuous min flow-max cut principle is used to reformulate the 'c
omplexity=volume' conjecture using Lorentzian flows. Conceptually\, discre
tized flows are interpreted in terms of `gatelines'\, one-dimensional time
-like curves that connect layers of a tensor network grid in the bulk spac
etime. We imagine each gateline represents a unitary operation such that t
he bulk calculation for complexity matches its information-theoretic defin
ition. The bulk symplectic potential provides a 'canonical' flow configura
tion characterizing perturbations around arbitrary CFT states. Its consist
ency requires the bulk to obey linearized Einstein's equations\, which are
shown to be equivalent to the holographic first law of complexity\, there
by advocating a notion of 'spacetime complexity'. Finally\, we explain the
need for a more general measure of complexity that captures the role of s
uboptimal flows or tensor network configurations. Based on 2105.12735 and
2106.12585.\n\n1) Please display your name when you join the seminar.\n\n2
) Your microphone is muted by default. Please only unmute it if you wish t
o make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rene Meyer (Würzburg U)
DTSTART:20220111T140000Z
DTEND:20220111T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/50
DESCRIPTION:Title: Symmetry-resolved quantum information measures for AdS g
ravity and beyond\nby Rene Meyer (Würzburg U) as part of GQFI-UGent-W
ST Seminars\n\n\nAbstract\nQuantum entanglement is the key resource employ
ed in modern quantum computation. Different entanglement measures such as
the entanglement entropy and Renyi entropies also provide useful informati
on about the entanglement structure of quantum field theories\, in particu
lar at critical points. I will discuss the symmetry resolved entanglement
and Renyi entropies\, a fine-grained version of the usual entanglement and
Renyi entropies\, both in the context of quantum field theory and AdS/CFT
. In the presence of global conserved charges\, they quantify the entangle
ment content of the reduced density matrix in a fixed charge sector. These
entanglement measures can in particular be calculated in two-dimensional
conformal field theories with U(1) Kac-Moody structure at level k\, and ar
e found to not depend on the value of the charge. This charge independence
is called equipartition of entanglement\, and implies that no charge sect
or is distinguished in terms of its entanglement content. Finally\, I will
discuss the symmetry resolved entanglement in the AdS3/CFT2 dual of the U
(1) Kac-Moody CFT. Agreement with CFT results provides a further test of t
he AdS3/CFT2 correspondence. I finish with some results about the violatio
n of the equipartition property in CFTs with W3 symmetry. This talk is bas
ed on hep-th/2012.11274 and hep-th/2108.09210.\n\n1) Please display your n
ame when you join the seminar.\n\n2) Your microphone is muted by default.
Please only unmute it if you wish to make a question or comment\, and then
mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Sasieta (Madrid IFT)
DTSTART:20220118T140000Z
DTEND:20220118T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/51
DESCRIPTION:Title: Holographic Complexity of Quantum Black Holes\nby Ma
rtin Sasieta (Madrid IFT) as part of GQFI-UGent-WST Seminars\n\n\nAbstract
\nIn this talk\, I will describe a way to characterize the bulk quantum co
rrections to holographic complexity proposals for the state of a black hol
e using double holography. The specific setup is the quantum BTZ black hol
e\, which encompasses in an exact manner the effects of conformal fields w
ith large central charge in the presence of the black hole\, including the
backreaction corrections to the BTZ metric. I will show how the Volume Co
mplexity admits a consistent quantum expansion\, while the Action Complexi
ty fails to account for the additional contributions from bulk quantum fie
lds and does not lead to the correct classical limit.\n\n1) Please display
your name when you join the seminar.\n\n2) Your microphone is muted by de
fault. Please only unmute it if you wish to make a question or comment\, a
nd then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rob Myers (Perimeter Institute)
DTSTART:20220125T140000Z
DTEND:20220125T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/52
DESCRIPTION:Title: Complexity=Anything\nby Rob Myers (Perimeter Institu
te) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nMotivated by hologra
phic complexity\, we examine a new class of gravitational observables in a
symptotically AdS space associated with codimension-one slices or with cod
imension-zero regions. We argue that any of these observables is an equal
ly viable candidate as the extremal volume for a gravitational dual of com
plexity.\n\n1) Please display your name when you join the seminar.\n\n2) Y
our microphone is muted by default. Please only unmute it if you wish to m
ake a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sridip Pal (IAS)
DTSTART:20220201T140000Z
DTEND:20220201T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/53
DESCRIPTION:Title: Automorphic Spectra and the Conformal Bootstrap\nby
Sridip Pal (IAS) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe poin
t out that the spectral geometry of hyperbolic manifolds provides a remark
ably precise model of the modern conformal bootstrap. As an application\,
we use conformal bootstrap techniques to derive rigorous computer-assisted
upper bounds on the lowest positive eigenvalue $\\lambda_1(X)$ of theLapl
ace-Beltrami operator on closed hyperbolic surfaces and 2-orbifolds $X$. I
n a number of notable cases\, our bounds are nearly saturated by known sur
faces and orbifolds. For instance\, our bound on all genus-2 surfaces $X$
is $\\lambda_1(X)\\leq 3.8388976481$\, while the Bolza surface has $\\lamb
da_1(X)\\approx 3.838887258$.\n\nI will explain that hyperbolic surface ar
e of the form \\Gamma\\G/K with G=PSL(2\,R)\, K=SO(2) /{\\pm I} and \\Gamm
a being Fuchsian group. For a given hyperbolic surface\, one can define a
Hilbert space of local operators\, transforming under unitary irreps of a
conformal group (PSL(2\,R)) and introduce a notion of operator product exp
anion (OPE). The associativity of this OPE reflects the associativity of f
unction multiplication on the space \\Gamma\\G and leads to the bootstrap
equations. Now the functions on \\Gamma\\G can be thought of automorphic f
orms on the surface \\Gamma\\G/K and I will show that the scaling dimensio
ns of these operators are in fact related to the automorphic spectra in pa
rticular the Laplacian eigenvalues on the surface. Hence the bootstrap equ
ations imply bound on the Laplacian eigenvalues.\n\nFinally\, I will make
some remarks about how our methods can be generalized to higher-dimensiona
l hyperbolic manifolds (or orbifolds) and to yield stronger bounds in the
two-dimensional case. This is based on a work (arXiv:2111.12716) with P. K
ravchuk and D. Mazac.\n\n1) Please display your name when you join the sem
inar.\n\n2) Your microphone is muted by default. Please only unmute it if
you wish to make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shota Komatsu (CERN)
DTSTART:20220208T150000Z
DTEND:20220208T160000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/54
DESCRIPTION:Title: Crosscap States in Integrable Field Theories and Spin Ch
ains\nby Shota Komatsu (CERN) as part of GQFI-UGent-WST Seminars\n\n\n
Abstract\nCrosscap states have been extensively studied in two-dimensional
conformal field theory in the past\, where part of the motivations came f
rom their connection to orientifolds in string theory. Surprisingly howeve
r\, analogous studies in (massive) integrable theories have been lacking.
In this talk\, I will fill this gap by presenting a systematic study of cr
osscap states in integrable field theories and spin chains. First\, I deri
ve an exact formula for overlaps between the crosscap state and any excite
d state in integrable field theories with diagonal scattering. Using the f
ormula\, I compute the crosscap entropy i.e. the overlap with the ground s
tate in several examples\, and find that it decreases monotonically along
the renormalization group flow except in cases where the discrete symmetry
is spontaneously broken in the infrared. We next introduce crosscap state
s in integrable spin chains and obtain exact determinant expressions for o
verlaps with energy eigenstates. These states are long-range entangled and
provide interesting initial conditions for the quantum quench protocol\,
which are quite distinct from short-range entangled states corresponding t
o the boundary states. As a side result\, I will also briefly comment on t
he interplay between fermionization and Bethe ansatz.\n\n1) Please display
your name when you join the seminar.\n\n2) Your microphone is muted by de
fault. Please only unmute it if you wish to make a question or comment\, a
nd then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dalimil Mazac (IAS)
DTSTART:20220215T140000Z
DTEND:20220215T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/55
DESCRIPTION:Title: Bootstrapping Boundaries and Branes\nby Dalimil Maza
c (IAS) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI will discuss b
ootstrap constraints on conformal boundary conditions in 2D CFTs. In parti
cular\, I will explain how to derive bounds on the boundary entropy starti
ng from the consistency of the annulus partition function. In the context
of string theory\, these imply a universal upper bound on the tension of s
table D-branes. It turns out that our bounds are often saturated by intere
sting boundary conditions in rational CFTs. In some cases\, the exact satu
ration can be proven using analytic functionals\, which is closely related
to the solution of the sphere packing problem in 8 and 24 dimensions. Our
bounds at large central charge have potential implications for end-of-the
-world branes in pure gravity on AdS_3. The talk will be based on https://
arxiv.org/pdf/2112.00750.pdf\, which is joint work with Scott Collier and
Yifan Wang.\n\n1) Please display your name when you join the seminar.\n\n2
) Your microphone is muted by default. Please only unmute it if you wish t
o make a question or comment\, and then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nima Lashkari (Purdue University)
DTSTART:20220222T140000Z
DTEND:20220222T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/56
DESCRIPTION:Title: Renormalization Group and Error Correction\nby Nima
Lashkari (Purdue University) as part of GQFI-UGent-WST Seminars\n\n\nAbstr
act\nIn renormalization group (RG) flow\, the low energy states form a cod
e subspace that is protected against the local short-distance errors. We w
ill discuss the similarities and differences between this approximate erro
r correction code and the classical and quantum codes that appear in the d
egenerate vacua of local many-body quantum systems. We will consider conti
nuous MERA as a concrete example and discuss how well the low-energy opera
tors are protected. The trade-off bounds set a bound on the amount of quan
tum information at a scale. Finally\, we will comment on the connections t
o the quantum error correction codes in holography.\n\n1) Please display y
our name when you join the seminar.\n\n2) Your microphone is muted by defa
ult. Please only unmute it if you wish to make a question or comment\, and
then mute it back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jacopo Viti (IIP)
DTSTART:20220301T140000Z
DTEND:20220301T150000Z
DTSTAMP:20260404T131146Z
UID:Holography_AdSCFT/57
DESCRIPTION:Title: The Classical Limit of the Entanglement Entropy\nby
Jacopo Viti (IIP) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nIt may
be naively assumed that certain entanglement measures\, like the entangle
ment entropy of a pure state\, approach zero in the classical limit. In th
is talk\, we show that the limit (when properly defined) is both well-beha
ved and nonzero: for a bipartite system of N particles\, it coincides with
the Shannon entropy of N bits. These results have been demonstrated previ
ously in the context of quantum field theory\, but here we derive them in
an elementary way and also provide a physical interpretation.\n\nWork in c
ollaboration with G. Mussardo\, to be published in PRA as Editor suggestio
n\, see https://arxiv.org/abs/2112.06840.\n\n1) Please display your name w
hen you join the seminar. 2) Your microphone is muted by default. Please
only unmute it if you wish to make a question or comment\, and then mute i
t back again.\n
LOCATION:https://stable.researchseminars.org/talk/Holography_AdSCFT/57/
END:VEVENT
END:VCALENDAR