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SUMMARY:Vijay Balasubramanian (UPenn)
DTSTART:20200507T190000Z
DTEND:20200507T200000Z
DTSTAMP:20260404T111000Z
UID:IFQ/1
DESCRIPTION:Title: Geometric secret sharing in a model of Hawking radiation\nby Vijay
Balasubramanian (UPenn) as part of It from Qubit\n\n\nAbstract\nWe conside
r a black hole in three dimensional AdS space entangled with an auxiliary
radiation system. We then model the microstates of the black hole in terms
of a field theory living on an end of the world brane behind the horizon\
, and allow this field theory to itself have a holographic dual geometry.
This geometry is also a black hole since entanglement of the microstates w
ith the radiation leaves them in a mixed state. This "inception black hole
" can be purified by entanglement through a wormhole with an auxiliary sys
tem which is naturally identified with the external radiation\, giving a r
ealization of the ER=EPR scenario. In this context\, we propose an extensi
on of the Ryu-Takayanagi (RT) formula\, in which extremal surfaces computi
ng entanglement entropy are allowed to pass through the brane into its dua
l geometry. This new rule reproduces the Page curve for evaporating black
holes\, consistently with the recently proposed "island formula". We then
separate the radiation system into pieces. Our extended RT rule shows that
the entanglement wedge of the union of radiation subsystems covers the bl
ack hole interior at late times\, but the union of entanglement wedges of
the subsystems may not. This result points to a secret sharing scheme in H
awking radiation wherein reconstruction of certain regions in the interior
is impossible with any subsystem of the radiation\, but possible with all
of it.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hrant Gharibyan (Caltech)
DTSTART:20200521T190000Z
DTEND:20200521T210000Z
DTSTAMP:20260404T111000Z
UID:IFQ/2
DESCRIPTION:Title: The Python's Lunch: geometric obstructions to decoding Hawking radiatio
n\nby Hrant Gharibyan (Caltech) as part of It from Qubit\n\n\nAbstract
\nHarlow and Hayden [arXiv:1301.4504] argued that distilling information o
ut of Hawking radiation is computationally hard despite the fact that the
quantum state of the black hole and its radiation is relatively un-complex
. I will trace this computational difficulty to a geometric obstruction in
the Einstein-Rosen bridge connecting the black hole and its radiation. In
spired by tensor network models\, I will present a conjecture that relates
the computational hardness of distilling information to geometric feature
s of the wormhole - specifically to the exponential of the difference in g
eneralized entropies between the two non-minimal quantum extremal surfaces
that constitute the obstruction. Due to its shape\, this obstruction was
dubbed "Python's Lunch"\, in analogy to the reptile's postprandial bulge.\
n
LOCATION:https://stable.researchseminars.org/talk/IFQ/2/
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SUMMARY:Jordan Cotler (Stanford)
DTSTART:20200616T200000Z
DTEND:20200616T220000Z
DTSTAMP:20260404T111000Z
UID:IFQ/3
DESCRIPTION:Title: AdS3 gravity and random CFT\nby Jordan Cotler (Stanford) as part of
It from Qubit\n\n\nAbstract\nWe compute the path integral of three-dimens
ional gravity with negative cosmological constant on spaces which are topo
logically a torus times an interval. These are Euclidean wormholes\, which
smoothly interpolate between two asymptotically Euclidean AdS3 regions wi
th torus boundary. From our results we obtain the spectral correlations be
tween BTZ black hole microstates near threshold\, as well as extract the s
pectral form factor at fixed momentum\, which has linear growth in time wi
th small fluctuations around it. The low-energy limit of these correlation
s is precisely that of a double-scaled random matrix ensemble with Virasor
o symmetry. Our findings suggest that if pure three-dimensional gravity ha
s a holographic dual\, then the dual is an ensemble which generalizes rand
om matrix theory.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ying Zhao (IAS)
DTSTART:20200421T200000Z
DTEND:20200421T220000Z
DTSTAMP:20260404T111000Z
UID:IFQ/4
DESCRIPTION:Title: A quantum circuit interpretation of evaporating black hole geometry
\nby Ying Zhao (IAS) as part of It from Qubit\n\n\nAbstract\nWhen Alice sh
ares thermofield double with Bob\, her time evolution can make the wormhol
e grow. We identify different kinds of operations Alice can do as being re
sponsible for the growth of different parts of spacetime and see how it fi
ts together with subregion duality. With this\, we give a quantum circuit
interpretation of evaporating black hole geometry. We make an analogy betw
een the appearance of island for evaporating black hole and the transition
from two-sided to one-sided black hole in the familiar example of perturb
ed thermofield double. If Alice perturbs thermofield double and waits for
scrambling time\, she will have a one-sided black hole with interior of he
r own. We argue that by similar mechanism the radiation gets access to the
interior (island forms) after Page time. The growth of the island happens
as a result of the constant transitions from two-sided to one-sided black
holes.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Don Marolf (UCSB)
DTSTART:20200409T203000Z
DTEND:20200409T223000Z
DTSTAMP:20260404T111000Z
UID:IFQ/5
DESCRIPTION:Title: Baby Universes and Black Hole Information\nby Don Marolf (UCSB) as
part of It from Qubit\n\n\nAbstract\nIn the 1980’s\, work by Coleman and
by Giddings and Strominger linked the physics of spacetime wormholes to
‘baby universes’ and an ensemble of theories. We revisit such ideas\,
using features associated with a negative cosmological constant and asympt
otically AdS boundaries to strengthen the results\, introduce a change in
perspective\, and connect with recent replica wormhole discussions of the
Page curve. A key new feature is an emphasis on the role of null states. W
e explore this structure in detail in simple topological models of the bul
k that allow us to compute the full spectrum of associated boundary theori
es. We also argue that similar properties must hold in any consistent gra
vitational path integral.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hong Liu (MIT)
DTSTART:20200716T190000Z
DTEND:20200716T210000Z
DTSTAMP:20260404T111000Z
UID:IFQ/6
DESCRIPTION:Title: Entanglement entropies of equilibrated pure states and replica wormhole
s\nby Hong Liu (MIT) as part of It from Qubit\n\n\nAbstract\nConsider
a quantum many-body system initially in a far-from-equilibrium pure state.
\n\nIf the system is non-integrable\, the state should approach equilibriu
m after some time.\n\nWe develop an approximation to calculate quantum inf
ormational properties of such an "equilibrated pure state.” Applied to
gravity systems\, the approximation leads to a derivation of replica wormh
oles discussed recently in the context of Page curves for black holes\, el
ucidating their mathematical origin\, physical interpretation\, and why t
hey lead to answers which are consistent with unitarity.\n\nBased on work
to appear with Shreya Vardhan.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pablo Bueno (Instituto Balseiro\, Bariloche)
DTSTART:20201021T190000Z
DTEND:20201021T201500Z
DTSTAMP:20260404T111000Z
UID:IFQ/7
DESCRIPTION:Title: Reflected entropy\, free fields and symmetries\nby Pablo Bueno (Ins
tituto Balseiro\, Bariloche) as part of It from Qubit\n\n\nAbstract\nA wel
l-defined notion of von Neumann entropy associated to pairs of spatial sub
regions has been recently proposed both in the holographic context and for
general QFTs. I will show that in the case of Gaussian systems ---and sim
ilarly to the entanglement entropy (EE)--- this "reflected entropy” can
be obtained in terms of correlation functions of the fields. In particular
\, I will present general formulas valid for free scalars and fermions in
arbitrary dimensions. I will apply the results to various free theories in
1+1 and 2+1 dimensions\, verifying that the conjectural monotonicity prop
erty $R(A\,BC)\\geq R(A\,B)$ and the general inequality $R(A\,B)\\geq I(A\
,B)$ hold in all cases. The results obtained suggest that for general regi
ons characterized by length-scales $L_A\\sim L_B \\sim L$ and separated a
distance $\\ell$\, the reflected entropy in the large-separation regime ($
x\\equiv L/\\ell \\ll 1$) is related to the mutual information by: $R(x) \
\sim −I(x) \\log x$ for general CFTs in arbitrary dimensions. Finally\,
I will argue that the notion of reflected entropy can be canonically gene
ralized in a way which is particularly suitable for theories obtained by r
estricting the full algebra of operators to those which are neutral under
global symmetry groups. A key role in the discussion is played by type-I v
on Neumann algebras\, which differ from the usual type-III algebras associ
ated to spatial subregions in QFT. I will perform various explicit compari
sons between both types of algebras.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Jafferis (Harvard)
DTSTART:20201113T190000Z
DTEND:20201113T210000Z
DTSTAMP:20260404T111000Z
UID:IFQ/8
DESCRIPTION:Title: Inside the Hologram\nby Daniel Jafferis (Harvard) as part of It fro
m Qubit\n\n\nAbstract\nI will discuss using probe black holes to explore t
he reconstruction of bulk operators. Under some assumptions\, modular flow
of the probes evolves nearby bulk operators in proper time along the prob
e trajectory. This includes cases where the evolution goes behind horizons
in the spacetime being probed.\n
LOCATION:https://stable.researchseminars.org/talk/IFQ/8/
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