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BEGIN:VEVENT
SUMMARY:From QFT to quantum gravity using the algebraic approach
DTSTART;VALUE=DATE-TIME:20230831T130000Z
DTEND;VALUE=DATE-TIME:20230831T140000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-826@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Kasia Rejzner ()\nIn this talk I will discuss how th
e algebraic approach to (perturbative) quantum field theory can benefit th
e search for the theory quantum gravity through several different approach
es. I will discuss the problem of constructing gauge invariant observables
\, the asymptotic safety program and consequences of potential discretenes
s of spacetime at small scales.\n\nhttps://indico.tpi.uni-jena.de/event/28
9/contributions/826/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/826/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The semiclassical Einstein equation in cosmological spacetimes: Ex
istence and uniqueness of the solutions
DTSTART;VALUE=DATE-TIME:20230829T144000Z
DTEND;VALUE=DATE-TIME:20230829T152000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-831@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nicola Pinamonti ()\nDuring this talk we shall discu
ss some properties of the semiclassical Einstein equation.\nThis equation
is used to model the backreaction of quantum matter on classical backgroun
ds.\nIn this talk we shall in particular analyze the case of backgrounds w
hich describe cosmological spacetimes.\nThe quantum field we shall conside
r is massive and satisfies a linear equation with a generic coupling to th
e scalar curvature.\nWe observe that a nonlocal term with higher order der
ivatives is present in the expectation value of the matter stress tensor w
hich sources gravity.\nThis term prevents a direct analysis of that equati
on\, we show how to deal with it in order to put the semiclassical equatio
n in a form which can then be treated with Banach fixed point methods.\n\n
https://indico.tpi.uni-jena.de/event/289/contributions/831/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/831/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Registration
DTSTART;VALUE=DATE-TIME:20230828T070000Z
DTEND;VALUE=DATE-TIME:20230828T072000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-863@indico.tpi.uni-jena.de
DESCRIPTION:https://indico.tpi.uni-jena.de/event/289/contributions/863/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/863/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Black Holes Decohere Quantum Superpositions
DTSTART;VALUE=DATE-TIME:20230831T073000Z
DTEND;VALUE=DATE-TIME:20230831T083000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-835@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Robert Wald (University of Chicago)\nWe show that if
a massive body is put in a quantum superposition of spatially separated s
tates\, the mere presence of a black hole in the vicinity of the body will
eventually destroy the coherence of the superposition. This occurs becaus
e\, in effect\, the gravitational field of the body radiates soft graviton
s into the black hole\, allowing the black hole to harvest "which path'' i
nformation about the superposition. A similar effect occurs for quantum su
perpositions of electrically charged\nbodies. The effect is very closely r
elated to the memory effect and infrared divergences at null infinity.\n\n
https://indico.tpi.uni-jena.de/event/289/contributions/835/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/835/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement structure of geometric states in holography
DTSTART;VALUE=DATE-TIME:20230829T073000Z
DTEND;VALUE=DATE-TIME:20230829T083000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-822@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Veronica Hubeny ()\nMotivated by a long-standing aim
to understand the emergence of spacetime and its relation to entanglement
in the context of gauge/gravity duality\, we study the relations between
subsystem entanglement entropies. These quantities are delimited by the s
o-called holographic entropy cone\, characterized conveniently by holograp
hic entropy inequalities or alternately by certain extreme states. This c
onstruct reveals a surprisingly rich structure\, whose intricacy grows rap
idly with the number of subsystems. We review recent progress in understa
nding the holographic entropy cone\, both from the perspective of the defi
ning inequalities as well as from that of the extreme rays\, both of which
seem to hint at a deeper organizational principle.\n\nhttps://indico.tpi.
uni-jena.de/event/289/contributions/822/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/822/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quasinormal modes of Schwarzschild de Sitter black holes from Liou
ville CFT
DTSTART;VALUE=DATE-TIME:20230828T144000Z
DTEND;VALUE=DATE-TIME:20230828T152000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-862@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Paolo Arnaudo (SISSA)\nWe consider black hole linear
perturbation theory in a four-dimensional Schwarzschild de Sitter backgro
und. The relevant differential equation is a Heun equation\, which is a se
cond order ODE with four regular singularities. After showing how the exac
t connection formulae for the Heun equation can be obtained from the semic
lassical limit of Virasoro conformal blocks\, we use these formulae to obt
ain the quantization condition which gives the quasinormal mode frequencie
s as series expansions in the radius of the black hole horizon. We conclud
e discussing how the method can be applied to different backgrounds\, such
as Kerr-de Sitter or asymptotically anti-de Sitter black holes\, emphasis
ing the problems in which the method is more effective.\n\nhttps://indico.
tpi.uni-jena.de/event/289/contributions/862/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/862/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gravity beyond General Relativity: Quantum Fluctuations and Nonlin
ear Dynamics
DTSTART;VALUE=DATE-TIME:20230828T130000Z
DTEND;VALUE=DATE-TIME:20230828T140000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-821@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Aaron Held (Jena University)\nI review the status of
the asymptotic safety program which posits a nonperturbative ultraviolet
completion of gravitational quantum field theory. In particular\, I put em
phasis (i) on systematic extensions of approximation schemes\, (ii) on the
role of field redefinitions\, and (iii) on observable consequences.\n\nTh
e latter naturally connects the asymptotic safety program to an effective
field theory approach for a joint theory of gravity and matter. Herein\, I
focus on the classical gravitational sector where I summarize recent prog
ress on formulating a well-posed initial data evolution of the nonlinear d
ynamics. \n\nThe interplay between both parts of my talk provides a potent
ial link between current astrophysical observations of black holes and our
fundamental assumptions about quantized gravity.\n\nhttps://indico.tpi.un
i-jena.de/event/289/contributions/821/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/821/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Semiclassical Einstein equations from holography and boundary dyna
mics
DTSTART;VALUE=DATE-TIME:20230828T095000Z
DTEND;VALUE=DATE-TIME:20230828T105000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-819@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Akihiro Ishibashi ()\nWe consider how to formulate s
emiclassical problems in the context of the AdS/CFT correspondence\, based
on the proposal of Compere and Marolf [arXiv:0805.1902]. Our prescription
involves the effective action with self-action term for boundary dynamica
l fields\, which can be viewed as imposing mixed boundary conditions for t
he gravity dual. We derive the semiclassical Einstein equations sourced by
boundary CFT stress-energy tensor. Analyzing perturbations of the hologra
phic semiclassical Einstein equations\, we find a universal parameter whic
h controls the contribution from boundary CFTs and specifies dynamics on t
he AdS boundary. As a simple example\, we examine the semiclassical Einste
in equations in 3-dimensions with 4-dimensional AdS gravity dual\, and sho
w that the boundary BTZ black hole with vanishing expectation value of the
stress-energy tensor becomes unstable due to the backreaction from quantu
m stress-energy tensor when the parameter exceeds a certain critical value
.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/819/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/819/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Poster session
DTSTART;VALUE=DATE-TIME:20230829T095000Z
DTEND;VALUE=DATE-TIME:20230829T105000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-824@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Andras Laszlo (Wigner Research Centre for Physics\,
Budapest)\, Cecilia Giavoni (LMU-Munich)\, Christian Schmidt (Theoretisch-
Physikalisches Institut Jena\, Germany)\, Felipe Portales Oliva (Federal U
niversity of ABC)\, Hristu Culetu (Ovidius University)\, Ka Hei Choi (Ludw
ig Maximilian University of Munich)\, Maik Reddiger (Anhalt University of
Applied Sciences)\, Maria Alberti (ITP Leipzig)\, Tyler McMaken (Universit
y of Colorado Boulder)\, sami viollet (CPT Marseille)\n"Facets of Unitarit
y Violation in Dynamical Spacetimes" by Ka Hei Choi (Ludwig Maximilian Uni
versity of Munich)\; \n"Gravity and the Superposition Principle" by Hristu
Culetu (Ovidius University)\;\n"The master Dyson-Schwinger equation and t
he Wilsonian renormalization group flows in a generally covariant setting"
by Andras Laszlo (Wigner Research Centre for Physics\, Budapest)\;\n"Unif
ormly accelerated particles and gravitational waves: The Unruh effect and
zero-Rindler-energy modes" by Felipe Portales-Oliva (Federal University of
ABC)\;\n"Towards a Probabilistic Foundation of Relativistic Quantum Theor
y: The One-Body Born Rule in Curved Spacetime" by Maik Reddiger (Anhalt Un
iversity of Applied Sciences)\;\n"Modelling quantum particles falling into
a black hole: the deep interior limit" by Sami Viollet (CPT Marseille)\;\
n"Scattering Analogy of Cosmological Particle Production in a BEC-Quantum
simulator" by Christian F. Schmidt (Friedrich-Schiller-Universität Jena)\
;\n"Hawking radiation around and inside rotating and accreting black holes
" by Tyler McMaken (ILA and the University of Colorado Boulder)\;\n"The Ut
ility of Lorentzian Network Histories" by Cecilia Giavoni (Munich)\nTBD by
Maria Alberti (Leipzig)\n\nhttps://indico.tpi.uni-jena.de/event/289/contr
ibutions/824/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/824/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum field simulator for dynamics in curved spacetime
DTSTART;VALUE=DATE-TIME:20230901T073000Z
DTEND;VALUE=DATE-TIME:20230901T083000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-832@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Stefan Floerchinger ()\nQuantum fields in curved spa
cetimes have many tantalizing theoretical properties\, for example particl
es are being produced by the time-dependence of the geometry. I will descr
ibe how quantum fields in geometries with spacetime curvature and differen
t cosmologies can be quantum-simulated with Bose-Einstein condensates in s
pecifically designed trapping potentials and with time-dependent interacti
on strengths. Analytical results for relativistic scalar fields in cosmolo
gies with 2+1 spacetime dimensions will be compared with recent experiment
al results obtained in Heidelberg laboratories.\n\nhttps://indico.tpi.uni-
jena.de/event/289/contributions/832/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/832/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Superradiance and quantum states on black hole space-times
DTSTART;VALUE=DATE-TIME:20230830T073000Z
DTEND;VALUE=DATE-TIME:20230830T083000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-839@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Elizabeth Winstanley ()\nWe consider the definition
of the Boulware and Hartle-Hawking states for quantum fields on black hole
space-times. The properties of these states on a Schwarzschild black hole
have been understood for many years\, but neither of these states has a d
irect analogue on a Kerr black hole. We show how superradiant modes play a
n important role in the definition of quantum states on Kerr. Superradianc
e is also possible on static black hole space-times\, in particular for a
charged scalar field on a Reissner-Nordstrom black hole. We explore whethe
r analogues of the Boulware and Hartle-Hawking states exist in this situat
ion.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/839/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/839/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stress-energy tensor on global anti-de Sitter space-time with Robi
n boundary conditions
DTSTART;VALUE=DATE-TIME:20230830T152000Z
DTEND;VALUE=DATE-TIME:20230830T154000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-814@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: siva namasivayam (University of Sheffield)\nWe study
the renormalised stress-energy tensor (RSET) for a massless\, conformally
\ncoupled scalar field on four dimensional anti-de Sitter space-time (adS4
). As ads4 is\nnot a globally hyperbolic space-time\, we impose boundary c
onditions on the space-time\nboundary to have a well posed quantum field t
heory. We use Dirichlet\, Neumann and\nRobin (mixed) boundary conditions a
pplied to the scalar field and compute both the\nvacuum (v.e.v.) and therm
al (t.e.v.) expectation values of the RSET. When either\nDirichlet or Neum
ann boundary conditions are applied\, the v.e.v of the RSET is a\nmultiple
of the space-time metric. Applying Robin boundary conditions break the un
derlying symmetry seen with the vacuum state\, and results in a RSET that
varies with\nthe space-time position. However\, for all Robin boundary con
ditions\, both the v.e.v and\nt.e.v. converge\, at the space-time boundary
\, to the common v.e.v.s seen when either\nDirichlet or Neumann boundary c
onditions are applied.\n\nhttps://indico.tpi.uni-jena.de/event/289/contrib
utions/814/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/814/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement harvesting from conformal vacuums between two Unruh-D
eWitt detectors moving along null paths
DTSTART;VALUE=DATE-TIME:20230830T134000Z
DTEND;VALUE=DATE-TIME:20230830T140000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-815@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Subhajit Barman (Indian Institute of Technology Madr
as)\nIt is well-known that the (1+1) dimensional Schwarzschild and spatial
ly flat FLRW spacetimes are conformally flat. This work examines entanglem
ent harvesting from the conformal field vacuums in these spacetimes betwee
n two Unruh-DeWitt detectors\, moving along outgoing null trajectories. In
(1+1) dimensional Schwarzschild spacetime\, we considered the Boulware an
d Unruh vacua for our investigations. In this analysis\, one observes that
while entanglement harvesting is possible in (1+1) dimensional Schwarzsch
ild and (1+3) dimensional de Sitter spacetimes\, it is not possible in the
(1+1) dimensional de Sitter background for the same set of parameters whe
n the detectors move along the same outgoing null trajectory. The qualitat
ive results from the Boulware and the Unruh vacuums are alike. Furthermore
\, we observed that the concurrence depends on the distance *d* between th
e two null paths of the detectors periodically\, and depending on the para
meter values\, there could be entanglement harvesting shadow points or reg
ions.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/815/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/815/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Towards the optimal experiment of gravity-induced quantum entangle
ment
DTSTART;VALUE=DATE-TIME:20230830T150000Z
DTEND;VALUE=DATE-TIME:20230830T152000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-800@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Tomohiro Fujita (Waseda Institute for Advanced Study
)\nRecently\, various experiments have been proposed to verify quantum ent
anglement induced by Newtonian gravitational interactions. However\, no fe
asible setup has yet been found that is certainly achievable with existing
techniques. To search for an optimal setup\, we compute the logarithmic n
egativity of two oscillators with arbitrary quadratic potential and couple
d by gravity. We find that unstable inverted oscillators generate gravity-
induced entanglement most quickly and are most resistant to decoherence fr
om environmental fluctuations. As such an example\, we propose an experime
nt of optical levitation of mirrors using the anti-spring effect.\n\nhttps
://indico.tpi.uni-jena.de/event/289/contributions/800/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/800/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum effect unique to gravity based on the weak equivalence pri
nciple
DTSTART;VALUE=DATE-TIME:20230830T144000Z
DTEND;VALUE=DATE-TIME:20230830T150000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-799@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Youka Kaku (Nagoya university)\nThe construction of
a quantum gravity theory remains a challenge. One of the difficulties stem
s from the lack of sufficient experimental evidence. As a first step towar
d the quantum gravity experiment\, Bose et al. proposed a low-energy exper
iment to test if Newtonian gravity can generate quantum entanglement or no
t. However\, they assumed that only gravity is mediating in the system\, a
nd their proposals fail when other quantum interactions come into play.\nT
o overcome this issue\, we explore an alternative experimental setup that
can distinguish gravity-induced entanglement and entanglement resulting fr
om other interactions. Specifically\, we investigate an interference exper
iment of a quantum clock particle that feels a weak gravitational field as
well as Coulomb potential. As a result\, we find that the interference do
es not recohere only when gravity induces entanglement\, while other cases
exhibit periodic decoherence and recoherence. Furthermore\, we discuss th
e deep connection between our experimental setup and the weak equivalence
principle.\nThis talk is based on the collaborated work with Y. Nambu\, S.
Maeda and Y. Osawa\, published in Phys.Rev.D 106 (2022) 12\, 126005.\n\nh
ttps://indico.tpi.uni-jena.de/event/289/contributions/799/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/799/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Why 5? Semi-classical analysis of a Kerr-AdS black hole in five di
mensions
DTSTART;VALUE=DATE-TIME:20230830T132000Z
DTEND;VALUE=DATE-TIME:20230830T134000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-804@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Alessandro Monteverdi (University of Sheffield)\nSom
e of the quantum properties of rotating black holes in (3+1)-dimensional s
pacetimes remain unresolved. However\, studying higher-dimensional cases m
ay provide insight into their behaviour. In this talk\, we investigate the
behaviour of a massive scalar field in a Kerr-AdS (4+1)-dimensional space
time. Specifically\, we focus on the existence of a Hartle-Hawking state\,
which is a vacuum state with important properties\, such as being a therm
al and Hadamard state\, which means that it is well-behaved and has a fini
te energy density.\nWhile the Hartle-Hawking state has been studied in var
ious types of black holes\, our focus is on rotating black holes where we
have observed a correlation between the presence of the light surface and
the existence of the Hartle-Hawking state. It should be noted that the Har
tle-Hawking state does not exist in Kerr black holes\, but it does exist i
n Kerr-AdS black holes. In four dimensions\, the analysis of this state is
very challenging\, but in five dimensions\, the enhanced symmetry of the
system simplifies the analysis. Finally\, by using the Hartle-Hawking stat
e\, we also present a method for evaluating observables\, starting with th
e vacuum polarization.\n\nhttps://indico.tpi.uni-jena.de/event/289/contrib
utions/804/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/804/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The vacuum strikes back: Black stars
DTSTART;VALUE=DATE-TIME:20230830T130000Z
DTEND;VALUE=DATE-TIME:20230830T132000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-807@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Julio Arrechea (Institute of Astrophysics of Andalus
ia)\nI will show that the repulsive effects associated to the zero-point e
nergies of quantum\nfields are capable of supporting ultracompact stars th
at overcome the compactness\nlimits present in general relativity for any
sphere in hydrostatic equilibrium. These\nobjects are self-consistent solu
tions in semiclassical gravity that incorporate\nthe backreaction of the r
enormalized stress-energy tensor (RSET) of quantum fields\nin vacuum. We a
rrive at stars of striking qualitative agreement through two in-\ndependen
t modelings of the RSET\, evidencing the generality and robustness of\nthi
s result. The main physical properties of these novel black hole mimickers
are\nreviewed.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/
807/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/807/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Graviton couplings on Hilbert space
DTSTART;VALUE=DATE-TIME:20230830T144000Z
DTEND;VALUE=DATE-TIME:20230830T150000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-798@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Christian Gass (University of Warsaw)\nA fresh attem
pt towards a quantum field theory of gravitons\ninteracting with matter is
based on the Fock space quantization of\nWigner's helicity 2 representati
on\, rather than canonical quantization\nof a massless rank-2 tensor field
. In this way\, all issues with\nindefinite state spaces\, overshooting de
grees of freedom\, gauge fixing\,\netc. are avoided. It turns out that qua
ntum consistency of this\napproach is exactly as restrictive on the struct
ure of the interactions\,\nas the postulate of general covariance in the c
anonical approaches\,\nto the extent that general covariance may be regard
ed as a\nquantum prediction\, rather than an assumed principle.\n\nhttps:/
/indico.tpi.uni-jena.de/event/289/contributions/798/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/798/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Relative entropy in de Sitter wedges and diamonds
DTSTART;VALUE=DATE-TIME:20230830T150000Z
DTEND;VALUE=DATE-TIME:20230830T152000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-808@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Markus B. Fröb (ITP\, Universität Leipzig\, German
y)\nThe role of entropy\, in particular entanglement entropy\, in quantum
field theory has become increasingly prominent\, and entropy has appeared
in relation with several primary research topics in QFT: area theorems\, c
theorems\, the AdS/CFT correspondence\, quantum null energy inequalities
etc. While von Neumann entropy\, the basic concept in information theory\,
is divergent in QFT and can thus only be defined in cutoff theories (e.g.
on a lattice)\, relative entropies are finite and can be directly defined
in the continuum QFT. In the framework of Tomita-Takesaki modular theory\
, the relative entropy between the vacuum and a coherent excitation can be
computed using the modular operator associated to the vacuum and the spac
etime region that one is interested in. Unfortunately\, its explicit form
is only known in a few special cases.\nUsing the known modular operator fo
r de Sitter wedges and a recent result for the modular operator for confor
mal fields in de Sitter diamonds\, we compute the relative entropy between
the de Sitter vacuum state and a coherent excitation thereof in these reg
ions. We show explicitly that the result is positive and monotone\, and th
us satisfies the expected properties for a relative entropy.\n\nhttps://in
dico.tpi.uni-jena.de/event/289/contributions/808/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/808/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Relative entropy and dynamical black holes
DTSTART;VALUE=DATE-TIME:20230830T152000Z
DTEND;VALUE=DATE-TIME:20230830T154000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-806@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Edoardo D'Angelo (Università di Genova)\nSince the
discovery of the Bekenstein-Hawking formula\, there had been many attempts
to derive the entropy of black holes from the entanglement between the de
grees of freedom inside and outside the event horizon. This entanglement e
ntropy reproduces the area-law\, but it suffers from divergences in the co
ntinuum limit. In this talk\, I show how to derive the Bekenstein-Hawking
entropy from the relative entropy\, which is well-defined also for continu
um theories such as QFT\, in the case of dynamical\, spherically symmetric
black holes. I first review the algebraic quantization of a free scalar f
ield on curved space-times\, and show how to compute its relative entropy
from the initial data at infinity. Using the back-reaction of a free\, sca
lar quantum field on the metric\, I show that a variation in the relative
entropy between coherent states of the field produces a variation of one-q
uarter of the black hole horizon area.\n\nhttps://indico.tpi.uni-jena.de/e
vent/289/contributions/806/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/806/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum energy inequalities in integrable models
DTSTART;VALUE=DATE-TIME:20230830T132000Z
DTEND;VALUE=DATE-TIME:20230830T134000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-802@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jan Mandrysch (Leipzig University)\nMany results in
general relativity rely crucially on classical energy conditions inflicted
on the stress-energy tensor. Quantum matter\, however\, violates these co
nditions since the energy density can fluctuate and in particular become a
rbitrarily negative at a point. Nonetheless quantum matter should have som
e reminiscent notion of stability\, which can be captured by so-called qua
ntum (weak) energy inequalities (QEIs)\, lower bounds of the smeared quant
um stress-energy tensor. QEIs could be proven in many free quantum field t
heories (QFT) on both flat and curved spacetimes. However\, it is less cle
ar what happens in models with self-interaction. \n\nWe will present numer
ical and analytical results on QEIs in a large class of 1+1d models referr
ed to as integrable QFTs. As particular examples we treat the O(n)-nonline
ar-sigma and sinh-Gordon model at 1- and 2-particle level. \n\nParts of th
e talk are based on https://arxiv.org/abs/2302.00063.\n\nhttps://indico.tp
i.uni-jena.de/event/289/contributions/802/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/802/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Boundary conditions and infrared divergences
DTSTART;VALUE=DATE-TIME:20230830T134000Z
DTEND;VALUE=DATE-TIME:20230830T140000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-803@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Luca Sinibaldi (University of Pavia)\nWe review the
procedure to construct ground and KMS states\, for real scalar fields whos
e dynamics is dictated by the Klein-Gordon equation\, on standard static L
orentzian manifolds with a time-like boundary. We observe that this constr
uction\, depending on which boundary condition we fix on the boundary\, do
es not always lead to a bi-distribution $w_2\\in \\mathcal{D}'(M\\times M)
$ for the two-point correlation function of the given state. The reason wh
y it fails to be a bi-distribution is the presence of infrared divergences
. We discuss an explicit example\, namely a real scalar field on Bertotti-
Robinson spacetime\, proving that infrared divergences occur when Neumann
boundary conditions are imposed at the time-like boundary\, while for thos
e of Robin-type the underlying two-point correlation function is a well de
fined bi-distribution of Hadamard form.\n\nhttps://indico.tpi.uni-jena.de/
event/289/contributions/803/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/803/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Linear Stability of Semiclassical Theories of Gravity
DTSTART;VALUE=DATE-TIME:20230830T130000Z
DTEND;VALUE=DATE-TIME:20230830T132000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-812@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Paolo Meda (University of Trento)\nA characteristic
feature of semiclassical theories of gravity involving the backreaction of
a quantum matter field is the presence of higher order derivatives in the
dynamical equations. Hence\, the appearance of pathological "runaway solu
tions" is often argued\, i.e.\, solutions of the linearized equations arou
nd a background spacetime that grow exponentially in time. In this talk\,
this issue is studied in a semiclassical toy model\, consists of a quantum
scalar field coupled with a classical scalar field in Minkowski spacetime
. This toy model mimics also the evolution induced by Semiclassical Einste
in Equations for linear perturbations on flat and cosmological spacetimes.
It is shown that\, if the quantum field which drives the backreaction is
massive\, then there are choices of the renormalization parameters for whi
ch the linear perturbations with compact spatial support decay polynomiall
y in time for large times\, thus indicating stability of the underlying se
miclassical solution.\n\nhttps://indico.tpi.uni-jena.de/event/289/contribu
tions/812/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/812/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spontaneous Hawking radiation in a Bose-Einstein condensate and an
alogue cosmological particle creation in a fluid of light
DTSTART;VALUE=DATE-TIME:20230901T095000Z
DTEND;VALUE=DATE-TIME:20230901T105000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-834@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Jeff Steinhauer ()\nWe confirm that Hawking radiatio
n from an analogue black hole in a Bose-Einstein condensate is spontaneous
\, thermal\, and stationary. Furthermore\, we follow the time evolution of
the Hawking radiation\, and compare and contrast it with the predictions
for real black holes. We observe the ramp up of the Hawking radiation\, si
milar to a real black hole. The end of the spontaneous Hawking radiation i
s marked by the formation of an inner horizon. The Maryland group predicte
d that particles emanating from the inner horizon can cause stimulated Haw
king radiation. We find that these stimulated Hawking pairs are directly o
bservable. We also present our observation of analogue cosmological partic
le creation in a 3-dimensional quantum fluid of light. The process is seen
to be spontaneous\, and in close quantitative agreement with the quantum-
field theoretical prediction. We find that the long-wavelength particles p
rovide a window to early times. This latter work introduces a new quantum
fluid\, as cold as an atomic Bose-Einstein condensate.\n\nhttps://indico.t
pi.uni-jena.de/event/289/contributions/834/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/834/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Welcome speech
DTSTART;VALUE=DATE-TIME:20230828T072000Z
DTEND;VALUE=DATE-TIME:20230828T073000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-837@indico.tpi.uni-jena.de
DESCRIPTION:https://indico.tpi.uni-jena.de/event/289/contributions/837/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/837/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anomalies and the stability of stars
DTSTART;VALUE=DATE-TIME:20230901T083000Z
DTEND;VALUE=DATE-TIME:20230901T091000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-833@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Ignacio Reyes ()\nWhat are the essential aspects of
quantum theory needed in order to understand compact relativistic objects?
Relying solely on universal properties of QFTs at high energies\, we show
that as a star contracts towards its Buchdahl radius the effects of the t
race anomaly become macroscopic at densities much below the Planck scale.
As a consequence the unstable modes of scalar fields disappear\, implying
the system recovers linear stability under scalar perturbations.\n\nhttps:
//indico.tpi.uni-jena.de/event/289/contributions/833/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/833/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Creases\, corners and caustics: non-smooth structures on black hol
e horizons
DTSTART;VALUE=DATE-TIME:20230829T130000Z
DTEND;VALUE=DATE-TIME:20230829T140000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-816@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Harvey Reall (Cambridge University)\nThe event horiz
on of a dynamical black hole is generically a non-smooth hypersurface. I s
hall describe the types of non-smooth structure that can arise on a horizo
n that is smooth at late time. This includes creases\, corners and caustic
points.\nI shall discuss ``perestroikas'' of these structures\, in which
they undergo a qualitative change at an instant of time. A crease perestro
ika gives an exact local description of the event horizon near the ``insta
nt of merger'' of a generic black hole merger. Other crease perestroikas d
escribe horizon nucleation or collapse of a hole in a toroidal horizon. I
shall discuss the possibility that creases contribute to black hole entrop
y\, and the implications of non-smoothness for higher derivative terms in
black hole entropy. This talk is based on joint work with Maxime Gadioux.\
n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/816/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/816/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cosmological solutions to the semiclassical Einstein equation with
Minkowski-like vacua
DTSTART;VALUE=DATE-TIME:20230831T152000Z
DTEND;VALUE=DATE-TIME:20230831T160000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-810@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Nicolai Rothe (rothe@math.tu-berlin.de)\nWe will dis
cuss some newly found solutions to the full massless semiclassical Einstei
n equation (SCE) in a cosmological setting (with Λ=0).\nAfter a short int
roduction to the relevant notions we present the SCE in a particular shape
which allows for the construction of certain vacuum states. These states
may be viewed as as the least possible generalization of the Minkowski vac
uum to general (cosmological) space-times. In this setting\, solving the S
CE breaks down into solving a certain ODE which can be approached numerica
lly and\, at least generically\, we obtain solutions that well fit physica
l expectations. Moreover\, these solutions indicate dark energy as a quant
um effect back-reacting on cosmological metrics and\, since in our model m
=Λ=0\, this may not be traced back to the occurrence of a non-vanishing r
enormalized cosmological constant. Also we will shortly discuss how our mo
del can be used to solve the cosmic horizon problem and we present paramet
er regimes in which it matches certain aspects of CMB physics.\n\nhttps://
indico.tpi.uni-jena.de/event/289/contributions/810/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/810/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adiabatic Ground states in Non-smooth Spacetimes.
DTSTART;VALUE=DATE-TIME:20230828T083000Z
DTEND;VALUE=DATE-TIME:20230828T091000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-805@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Yafet Erasmo Sanchez Sanchez ()\nThe analysis of qua
ntum states in non-smooth spacetimes has two main motivations. First\, the
re are several models of physical phenomena that require spacetime metrics
with finite regularity. These include models of gravitational collapse\,
astrophysical objects and general relativistic fluids. Second\, the well-p
osedness of Einstein’s equations\, viewed as a system of hyperbolic PDE
requires spaces with finite regularity.\n\n\nGround states are a well-know
n class of Hadamard states in smooth spacetimes. \nIn this talk\, I will p
resent our proof that the ground state of the Klein–Gordon field in a no
n-smooth ultra static spacetime is an adiabatic state characterised by a S
obolev Wavefront set condition that depends on the regularity of the metri
c.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/805/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/805/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Characteristic renormalization and applications to black hole form
ation
DTSTART;VALUE=DATE-TIME:20230831T144000Z
DTEND;VALUE=DATE-TIME:20230831T152000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-809@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Daan Janssen (University of Leipzig)\nWe present a r
egularization prescription for Hadamard two-point functions defined on the
boundary of a lightcone\, which can be used to analyze renormalized quant
ities for linear scalar fields in a curved background. This can be applied
to formulate the semi-classical Einstein equations as a characteristic in
itial value problem. Furthermore\, we shall discuss how these tools can be
used to estimate backreaction effects of quantum fields near gravitationa
lly collapsing bodies and study formation of horizons and singularities in
semi-classical gravity.\n\nhttps://indico.tpi.uni-jena.de/event/289/contr
ibutions/809/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/809/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum Effects on Black Hole Cauchy Horizons
DTSTART;VALUE=DATE-TIME:20230830T095000Z
DTEND;VALUE=DATE-TIME:20230830T105000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-829@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Noah Zilberman ()\nBlack hole spacetimes harbor intr
icate internal structures\, featuring geometry that extends through an inn
er horizon to another external universe. This regularity of the inner hori
zon\, which plays the causal role of a Cauchy horizon\, challenges predict
ability within black holes. The strong cosmic censorship conjecture offers
a solution\, asserting that the Cauchy horizon becomes sufficiently irreg
ular under perturbations\, hence negating its existence. While this scenar
io is known to hold classically in some cases\, its validity amidst quantu
m perturbations remains an open question.\nAnswering this question require
s understanding how quantum energy fluxes influence the internal geometry
of black holes\, particularly at the inner horizon. A divergence in these
fluxes could dramatically alter the internal structure\, potentially resto
ring predictability by rendering the inner horizon impassable. Recent work
s have conquered the challenge of computing semiclassical energy fluxes (T
_{uu} and T_{vv} stress-energy tensor components in Eddington coordinates)
\nwithin black hole interiors\, shedding light on the nature of the Cauchy
horizon under quantum backreaction.\nMy talk outlines these recent advanc
ements\, presenting results in both asymptotically at (Zilberman\,Casal
s\,Ori&Ottewill) and asymptotically deSitter (Hollands\,Zahn&Wald) cases\,
briefly mentioning possible implications for the inner horizon traversabi
lity.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/829/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/829/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mode-Sum Renormalization in Black Hole Spacetimes
DTSTART;VALUE=DATE-TIME:20230829T083000Z
DTEND;VALUE=DATE-TIME:20230829T091000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-823@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Peter Taylor ()\nIt is well known that the expectati
on value of the stress-energy tensor for a quantum field must be renormali
zed. While there exists a well-understood formal resolution to the renorma
lization problem\, the practical implementation is technically difficult i
n black hole spacetimes. The first successful computation of the renormali
zed stress-energy tensor in a black hole spacetime dates back to seminal w
ork in the 1980s by Candelas and Howard. However\, there had been little i
mprovement on their prescription in the intervening decades\, despite some
drawbacks to their method. In recent years\, alternative approaches to co
mputing renormalized stress-energy tensors in black hole spacetimes have e
merged. I will discuss one such scheme that has proved very efficient in s
tatic black hole spacetimes in arbitrary dimensions. As an application of
this method\, I will also present results for the renormalized stress-ener
gy tensor for scalar fields in the Hartle-Hawking\, Unruh and Boulware sta
tes in the Reissner-Nordstrom spacetime.\n\nhttps://indico.tpi.uni-jena.de
/event/289/contributions/823/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/823/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The quantum scalar field on Kerr-de Sitter
DTSTART;VALUE=DATE-TIME:20230830T083000Z
DTEND;VALUE=DATE-TIME:20230830T091000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-801@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Christiane Klein (Universität Leipzig)\nIn order to
study physical effects of quantum fields on curved spacetimes\, one needs
appropriate\nHadamard states to describe the fields. In this talk\, we pr
esent a rigorous construction\, including\nthe proof of the Hadamard prope
rty\, of the Unruh state for the free scalar field on slowly rotating\nKer
r-de Sitter spacetimes. We sketch how this state can be used to compute th
e stress-energy tensor of the quantum field and present some results of th
is computation.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/
801/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/801/
END:VEVENT
BEGIN:VEVENT
SUMMARY:On the global Hadamard parametrix in QFT and the signed squared ge
odesic distance defined in domains larger than convex normal neighbourhood
s
DTSTART;VALUE=DATE-TIME:20230831T095000Z
DTEND;VALUE=DATE-TIME:20230831T105000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-813@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Valter Moretti (University of Trento)\nWe consider t
he global Hadamard condition and the notion of Hadamard parametrix whose u
se is pervasive in algebraic QFT in curved spacetime (see references in th
e main text). We point out the existence of a technical problem in the lit
erature concerning well-definedness of the global Hadamard parametrix in n
ormal neighbourhoods of Cauchy surfaces. We discuss in particular the defi
nition of the (signed) geodesic distance and related structures in an open
neighbourhood of the diagonal of larger than UxU\, for a normal convex n
eighbourhood U\, where (M\, g) is a Riemannian or Lorentzian (smooth Hausd
orff paracompact) manifold. We eventually propose a quite natural solution
which slightly changes the original definition by Kay and Wald and relies
upon some non-trivial consequences of the paracompactness property. The p
roposed re-formulation is in agreement with Radzikowski’s microlocal ver
sion of the Hadamard condition.\n(From Letters in Mathematical Physics vol
ume 111\, Article number: 130 (2021) )\n\nhttps://indico.tpi.uni-jena.de/e
vent/289/contributions/813/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/813/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Infrared Finite Scattering Theory in QFT and Quantum Gravity
DTSTART;VALUE=DATE-TIME:20230831T083000Z
DTEND;VALUE=DATE-TIME:20230831T091000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-811@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Gautam Satishchandran (Princeton University)\nA long
-standing problem in QFT and quantum gravity is the construction of an “
IR-finite" S-matrix. In the gravitational case\, the existence of these
“infrared divergences” is intimately tied to the “memory effect” (
i.e. the permanent displacement of test masses due to the passage of a gra
vitational wave). In this talk\, I shall explain the origin of these conne
ctions and illustrate that the construction of an IR-finite S-matrix requi
res the inclusion of states with memory (which do not lie in the standard
Fock space). In massive QED an elegant solution to this problem was provid
ed by Faddeev and Kulish who constructed an incoming/outgoing Hilbert spac
e of charged particles “dressed” with memory. We illustrate the ``pref
erred status'' of such states and their relationship to the superselection
structure of QED. However\, we show that this construction fails in the c
ase of massless QED\, Yang-Mills theories\, linearized quantum gravity wit
h massless/massive sources\, and in full quantum gravity. In the case of q
uantum gravity\, we prove that the only "Faddeev-Kulish" state is the vacu
um state. We also show that “non-Faddeev-Kulish” representations are a
lso unsatisfactory. Thus\, in general\, it appears there is no preferred H
ilbert space for scattering in QFT and quantum gravity. We argue that\, at
a fundamental level\, one must formulate scattering theory without an a p
riori choice of Hilbert space. We outline the framework of such a manifest
ly IR-finite scattering theory.\n\nhttps://indico.tpi.uni-jena.de/event/28
9/contributions/811/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/811/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The euclidean vacuum state for linearized gravity on de Sitter spa
cetime
DTSTART;VALUE=DATE-TIME:20230828T073000Z
DTEND;VALUE=DATE-TIME:20230828T083000Z
DTSTAMP;VALUE=DATE-TIME:20240305T114332Z
UID:indico-contribution-289-817@indico.tpi.uni-jena.de
DESCRIPTION:Speakers: Christian Gérard ()\nWe will explain the constructi
on of the euclidean vacuum state for linearized gravity on de Sitter space
time by a rigorous version of Wick rotation. We will discuss issues rela
ted to gauge invariance\, positivity and invariance under de Sitter isomet
ries.\n\nhttps://indico.tpi.uni-jena.de/event/289/contributions/817/
LOCATION:Leipzig University
URL:https://indico.tpi.uni-jena.de/event/289/contributions/817/
END:VEVENT
END:VCALENDAR