BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:Status of Birkhoff's theorem in polymerized semiclassical regime o
f Loop Quantum Gravity
DTSTART;VALUE=DATE-TIME:20240223T165500Z
DTEND;VALUE=DATE-TIME:20240223T172000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-646@indico.ecap.work
DESCRIPTION:Speakers: Luca Cafaro (University of Warsaw)\nThe collapse of
a spherically symmetric ball of pressureless dust has been intensively stu
died in Loop Quantum Gravity (LQG). From a quantum theory\, it is possible
to recover a semiclassical regime through a polymerization procedure.\n\n
In this setting\, general solutions to the polymerized Einstein field equa
tions (PEFE) will be discussed both for the interior and the exterior of t
he dust cloud. Exterior solutions are particularly interesting since they
may lead to a semiclassical version of Birkhoff's theorem. It is seen that
if time independence of the vacuum is imposed\, there exists a unique cla
ss of solutions depending on a constant. Nevertheless\, the possibility of
more intricate time dependent solutions is not ruled out completely. \n\n
Ultimately\, these results will be compared to a model of spherical collap
se obtained independently from the Einstein equations.\n\nhttps://indico.e
cap.work/event/67/contributions/646/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/646/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Should we learn to do physics with global observables?
DTSTART;VALUE=DATE-TIME:20240221T163500Z
DTEND;VALUE=DATE-TIME:20240221T170000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-645@indico.ecap.work
DESCRIPTION:Speakers: Marios Christodoulou (IQOQI Vienna )\nI present a sy
nthesis of ideas based on ongoing work with collaborators and inspired fro
m the debate in the context of table top quantum gravity and going all the
way back to the hole argument\, that suggest invariance under permutation
s as a fundamental symmetry for quantum gravity. I discuss implications\,
in particular that all observables would be expected to be global observab
les.\n\nhttps://indico.ecap.work/event/67/contributions/645/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/645/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Diffeomorphism invariant Fock states in LQG
DTSTART;VALUE=DATE-TIME:20240220T175000Z
DTEND;VALUE=DATE-TIME:20240220T181500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-644@indico.ecap.work
DESCRIPTION:Speakers: Waleed Sherif ()\nIn this talk\, I will present a Fo
ck space structure that can be naturally equipped to the diffeomorphism in
variant Hilbert space of loop quantum gravity (LQG)\, under certain assump
tions. In it\, the role of one-particle excitations is played by the diffe
omorphism invariant states based on graphs with a single (linked) componen
t. While the structure of the single-particle Hilbert space in this contex
t can be arbitrarily complex\, I will show that we can\, nevertheless\, qu
antitatively write some condensate states of group field theory (GFT) as d
iffeomorphism invariant coherent Fock states in LQG hence formally bridgin
g between the two approaches. I will also comment on the quantum geometry
of these single and multi-particle states and how can they be tentatively
interpreted as well as discuss how the coherent states obtained in this wo
rk relate to a more general concept of graph coherent states previously pr
oposed by M. Assanioussi (Phys. Rev. D 101\, 124022).\n\nhttps://indico.ec
ap.work/event/67/contributions/644/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/644/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum geometry of the null cone
DTSTART;VALUE=DATE-TIME:20240223T131500Z
DTEND;VALUE=DATE-TIME:20240223T140000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-643@indico.ecap.work
DESCRIPTION:Speakers: Wolfgang Wieland (FAU Erlangen-Nürnberg)\nWe presen
t a non-perturbative quantization of gravitational null initial data. Our
starting point is the characteristic null initial problem for tetradic gra
vity with a parity-odd Holst term in the bulk. After a basic review about
the resulting Carrollian boundary field theory\, we introduce a specific c
lass of impulsive radiative data. This class is defined for a specific cho
ice of relational clock. The clock is chosen in such a way that the shear
of the null boundary follows the profile of a step function. The angular d
ependence is arbitrary. Next\, we solve the residual constraints\, which a
re the Raychaudhuri equation and a Carrollian transport equation for an SL
(2\,R) holonomy. We show that the resulting submanifold in phase space is
symplectic. Along each null generator\, we end up with a simple mechanical
system. The quantization of this system is straightforward. Our basic str
ategy is to start from an auxiliary Hilbert space with constraints. The ph
ysical Hilbert space is the kernel of a constraint\, which is a combinatio
n of ladder operators. The constraint and its hermitian conjugate are seco
nd-class. Solving the constraint amounts to imposing a simple recursion re
lation for physical states. On the resulting physical Hilbert space\, the
SL(2\,R) Casimir is a Dirac observable. This observable determines the spe
ctrum of the two radiative modes. The area at the initial and final cross
sections are Dirac observables as well. They have a discrete spectrum\, wh
ich agrees with earlier results on this topic.\n\nhttps://indico.ecap.work
/event/67/contributions/643/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/643/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effective theory for regular black holes
DTSTART;VALUE=DATE-TIME:20240223T163000Z
DTEND;VALUE=DATE-TIME:20240223T165500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-642@indico.ecap.work
DESCRIPTION:Speakers: Hongguang Liu (FAU Erlangen)\nRecently\, models with
different properties have been proposed for regular black holes. To fully
understand their properties and differences\, we provide a systematic ana
lysis for the classification and construction of effective polymerized sph
erically symmetric models as $1+1$d field theory. We apply this formalism
and consider models that have the following advantages: The effective dyna
mics can be derived from a class of extended mimetic gravity Lagrangian in
4 dimensions. The models admit a consistent Lemaitre-Tolman-Bondi (LTB) c
ondition\, by which the dynamics is completely decoupled along the radial
direction in LTB coordinates\, trivializing the junction condition in dust
collapse. The class of effective dynamics admits a polymerized Birkhoff-l
ike theorem\, which leads to a stationary effective metric in the polymeri
zed vacuum. In this talk I will give an overview of this classification an
d describe the procedure for the reconstruction of the underlying effectiv
e dynamics and (inhomogeneous) dust collapse solutions from stationary sol
utions or vice versa. Examples include several well-known regular black ho
le solutions\, such as the Bouncing\, Bardeen\, and Hayward black holes.\n
\nhttps://indico.ecap.work/event/67/contributions/642/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/642/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Constraining Quantum Gravity Polymer Parameters through Gravitatio
nal Wave Observations
DTSTART;VALUE=DATE-TIME:20240223T174500Z
DTEND;VALUE=DATE-TIME:20240223T181000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-641@indico.ecap.work
DESCRIPTION:Speakers: Yaser Tavakoli ()\nIn this presentation\, I will fir
st discuss the theoretical characteristics of polymerized gravitational wa
ves (GWs). Subsequently\, I will present empirical limitations on the poly
mer scale concerning polymer GWs within a classical background spacetime.
These constraints will be derived from variations in the propagation speed
of GWs. By leveraging data from reputable sources such as the inter-detec
tor arrival time delays from the LIGO-Virgo Collaboration's GWTC1\, and th
e arrival time disparities between the GW signal GW170817 and its correspo
nding gamma-ray burst GRB170817A\, we will deduce restrictions on the poly
mer parameters.\n\nhttps://indico.ecap.work/event/67/contributions/641/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/641/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gravity and the Superposition Principle
DTSTART;VALUE=DATE-TIME:20240220T172500Z
DTEND;VALUE=DATE-TIME:20240220T175000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-637@indico.ecap.work
DESCRIPTION:Speakers: Hristu Culetu (Ovidius University)\nThe relation bet
ween gravity and quantum mechanics is investigated\nin this work. The link
is given by the wave packet expansion process\,\nrooted from the Uncertai
nty Principle. The basic idea is to express the\nde Broglie wavelength use
d by Schrodinger for a massive particle in terms\nof the associated Compto
n wavelength which is replaced by the Michell-Laplace radius $Gm/c^{2}$ of
the spherical object of mass $m ≥ m_{P}$ \, where $m_{P}$\nis the Planc
k mass.\n The wave packet spreading is studying in spherical coordinates\
, having the width $σ(t)$\, expressed in terms of G and c instead of $\\h
bar$. Therefore\,for masses larger than the Planck mass\, a faster dispers
ion rate of $σ(t)$ is obtained\, compared to the standard case. The dispe
rsion of the wave packet is observed only by a free falling observer and t
he process breaks down once the observer hits the surface of the object. \
n Different freely falling observers notice different rates of expansion
of the wave packet and the source of gravity is in a quantum superposition
. We further confront the Mita formula for the mean energy of the wave pac
ket with the de Broglie-Bohm quantum potential energy when the Schrodinger
equation is expressed in the Madelung form.\n\nhttps://indico.ecap.work/e
vent/67/contributions/637/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/637/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Exploring Quantum Reference Frames - Part II: Identification of E
vents\, Spacetimes in Superposition\, and a Quantum Hole Argument
DTSTART;VALUE=DATE-TIME:20240220T154000Z
DTEND;VALUE=DATE-TIME:20240220T160500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-618@indico.ecap.work
DESCRIPTION:Speakers: Anne-Catherine de la Hamette (University of Vienna /
IQOQI Vienna)\nConsider a scenario involving a superposition of semiclass
ical spacetimes. How can one compare points on the different manifolds acr
oss the superposition? Due to the diffeomorphism invariance of general rel
ativity\, there is a priori no notion of the “same” or “different”
points across the branches. In fact\, there are multiple ways of relating
points or events on the different spacetimes. Here\, we make this concret
e by using coincidences of four scalar fields to construct a comparison ma
p between all spacetimes in superposition\, which allows us to determine w
hether an event is located at the “same” or “different” points acr
oss the branches. Different choices of scalar fields can be understood as
different instantiations of quantum reference frames (QRFs)\, connecting t
he construction to recent research in the field of quantum foundations. As
explicit applications of this formalism\, we explore how the localization
of events is relative to the choice of QRF and will discuss the implicati
ons thereof for indefinite causal order and the locality of interaction. A
fter examining the construction of relational observables\, we conclude wi
th a quantum generalization of the famous hole argument. This argument cal
ls into question the metaphysical meaning of not just spacetime points but
also the identification between spacetime points across manifolds in supe
rposition.\n\nhttps://indico.ecap.work/event/67/contributions/618/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/618/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effects of the inflaton potential on the primordial power spectrum
in Loop Quantum Cosmology
DTSTART;VALUE=DATE-TIME:20240222T154000Z
DTEND;VALUE=DATE-TIME:20240222T160500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-611@indico.ecap.work
DESCRIPTION:Speakers: Jesús Yébana Carrilero (Instituto de Estructura de
la Materia IEM-CSIC)\nIn scenarios of physical interest in Loop Quantum C
osmology\, with a preinflationary epoch where the kinetic energy of the in
flaton dominates\, the analytic study of the dynamics of the primordial fl
uctuations has already been carried out by neglecting the inflaton potenti
al. In this talk\, we develop approximations to investigate the influence
of the potential as the period of kinetic dominance gives way to the infla
tionary regime. Treating the potential as a perturbation\, we discuss how
it modifies the effective mass that dictates the dynamics of the scalar pe
rturbations\, within the framework of hybrid Loop Quantum Cosmology. Compa
red to previous works\, we introduce a transition period that connects the
kinetically dominated regime with inflation\, as well as the main modific
ations coming from a slow-roll correction to a purely de Sitter evolution
during the inflationary period. Starting from initial conditions given by
a non-oscillating vacuum determined by an asymptotic Hamiltonian diagonali
zation\, we then analytically compute the primordial power spectrum for a
quadratic inflation potential. We finally explain the corrections that the
inflaton potential produces in this spectrum.\n\nhttps://indico.ecap.work
/event/67/contributions/611/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/611/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asymptotic safety and the road towards running relational observab
les
DTSTART;VALUE=DATE-TIME:20240222T143000Z
DTEND;VALUE=DATE-TIME:20240222T151500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-620@indico.ecap.work
DESCRIPTION:Speakers: Renata Ferrero ()\nAsymptotic safety is a UV complet
ion of quantum gravity most commonly realized via a non-trivial fixed poin
t of the Functional Renormalization Group (FRG) flow. The FRG takes the me
tric as the carrier field of the gravitational degrees of freedom\, and th
e effective action functionals depend on the metric in a diffeomorphism-in
variant way.\nIn my talk\, I will introduce an approach to compute the RG
flow of relational observables which evolve from their microscopic expres
sions towards the full quantum expectation value. As a first application
I will consider four scalar fields coupled to gravity to represent the phy
sical coordinate frame from which relational observables can be constructe
d.\nThis allows access to universal critical exponents of the observables.
As such the computation of these scaling relations can serve as a way to
compare with different approaches to quantum gravity.\n\nhttps://indico.ec
ap.work/event/67/contributions/620/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/620/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Exploring Quantum Reference Frames - Part I: Frame Dependence and
How to Compare Objects across a Superposition
DTSTART;VALUE=DATE-TIME:20240220T151500Z
DTEND;VALUE=DATE-TIME:20240220T154000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-626@indico.ecap.work
DESCRIPTION:Speakers: Viktoria Kabel ()\nWhen describing a physical system
\, it is very common to do so with respect to a reference frame - a ruler
used to determine the position of a particle\, for example\, or a clock\,
which tracks the time that elapses while it is moving. Usually\, reference
frames are treated as purely classical objects with well-defined properti
es. But what happens if we take into account the quantum properties of the
reference frame itself? This question has motivated a recent wave of rese
arch on *quantum reference frames* (QRFs)\, which investigates how the des
cription of our world changes when described relative to different quantum
systems. \n\nChanges of QRFs have a variety of interesting implications.
Quantum features previously thought to be absolute\, such as superposition
and entanglement\, suddenly become dependent on the frame. In fact\, what
we even mean by the same location\, spin\, or even subsystem across diffe
rent branches of a superposition can change when describing the system wit
h respect to different QRFs. Here\, we introduce a generalized\, visual fr
amework that provides a deeper understanding of this phenomenon by relatin
g the frame dependence to the fundamental question of how to identify and
compare objects across a superposition. This becomes particularly relevant
in the context of spacetimes in superposition\, where there is a priori n
o notion of ”the same” or “different” points across the different
possible worlds. With this newfound understanding\, we explore the implica
tions for scenarios at the interface between quantum physics and gravity\,
such as the gravitational field sourced by a massive object in superposit
ion.\n\nhttps://indico.ecap.work/event/67/contributions/626/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/626/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Uniqueness of the Fock quantization of a massless scalar field in
Kantowski-Sachs spacetime and its Hamiltonian.
DTSTART;VALUE=DATE-TIME:20240219T163000Z
DTEND;VALUE=DATE-TIME:20240219T165500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-630@indico.ecap.work
DESCRIPTION:Speakers: Alvaro Torres-Caballeros (CSIC\, Madrid)\nWe discuss
a criterion to guarantee the uniqueness of the Fock quantization of a mas
sless free scalar field in a Kantowski-Sachs background. In general spacet
imes\, the infinite ambiguity of choosing a set of annihilation and creati
on operators leads to non-equivalent Fock representations\, a fact that is
due to the unavailability of a privileged vacuum state in the theory. In
the case of a Kantowski-Sachs spacetime\, we show that the problem can be
overcome by imposing invariance under the spatial symmetries of the backgr
ound and a quantum dynamics that admit a unitary implementation. We also s
how that this criterion fixes the freedom for background-dependent scaling
s involved in the choice of creation and annihilation variables. The remai
ning freedom for background-dependent changes can be employed to attain a
Hamiltonian for the scalar field that is asymptotically diagonal in the ul
traviolet sector. These results may find applications in the quantization
of matter fields and perturbations on anisotropic cosmologies and\, morevo
er\, on the interior of nonrotating black hole spacetimes.\n\nhttps://indi
co.ecap.work/event/67/contributions/630/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/630/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A black hole interior model in Loop Quantum Cosmology
DTSTART;VALUE=DATE-TIME:20240219T143000Z
DTEND;VALUE=DATE-TIME:20240219T151500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-634@indico.ecap.work
DESCRIPTION:Speakers: Guillermo A. Mena Marugán (IEM\, CSIC)\nThe study o
f the quantum geometry of nonrotating black holes has received a lot of at
tention within the framework of Loop Quantum Cosmology. This interest has
been revitalized since the introduction of an effective model by Ashtekar\
, Olmedo\, and Singh. Despite recent advances\, there are certain question
s about its quantization that remain open. We complete this quantization t
aking as starting point an extended phase space formalism. Adopting standa
rd prescriptions in Loop Quantum Cosmology and searching for quantum solut
ions to the Hamiltonian constraint in a sufficiently large set of states\,
we show how to build a physical Hilbert space with a continuous range of
black hole mass. This fact seems in favour of a conventional classical lim
it (at least for large masses). We also briefly comment on the extension t
o the exterior geometry\, the introduction of a scalar field\, and the con
sideration of perturbations.\n\nhttps://indico.ecap.work/event/67/contribu
tions/634/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/634/
END:VEVENT
BEGIN:VEVENT
SUMMARY:An effective metric from group field theory: implications for cosm
ology
DTSTART;VALUE=DATE-TIME:20240219T172000Z
DTEND;VALUE=DATE-TIME:20240219T174500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-625@indico.ecap.work
DESCRIPTION:Speakers: Lisa Mickel (University of Sheffield)\nGroup field t
heory (GFT) is a background independent approach to quantum gravity that h
as been successfully applied to the cosmological setting and shown to have
the potential for rich phenomenology. In this talk we will explore a nove
l proposal to construct operators in GFT based on symmetries of the action
\, whose expectation values can be interpreted as giving rise to an effect
ive metric originating directly from the quantum theory. This construction
relies on a relational coordinate system spanned by four massless scalar
fields. We proceed to investigate the implications of this proposition for
a flat homogeneous universe and its perturbations.\n\nhttps://indico.ecap
.work/event/67/contributions/625/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/625/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effective LTB and generalized analysis of a dust collapse
DTSTART;VALUE=DATE-TIME:20240219T174500Z
DTEND;VALUE=DATE-TIME:20240219T181000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-640@indico.ecap.work
DESCRIPTION:Speakers: Stefan Weigl (Institute for Quantum Gravity\, FAU Er
langen-Nürnberg)\nBased on our work of embedding generalized (effective)
LTB models into polymerized spherically symmetric models as a 1 + 1 field
theory model\, I provide in this talk a way to construct effective LTB mod
els that have a dynamically stable LTB condition\, obey a notion of covari
ance and further are consistent with the improved dynamics of LQC. I will
show various aspects of this approach and compare it with different phenom
enological models by discussing areal gauge fixing\, a polymerized vacuum
solution and an Oppenheimer-Snyder dust collapse model. It turns out that
a symmetric bounce is typical for these models and that shock solutions ar
e absent.\n\nhttps://indico.ecap.work/event/67/contributions/640/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/640/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Scalar cosmological perturbations from quantum-gravitational entan
glement
DTSTART;VALUE=DATE-TIME:20240222T151500Z
DTEND;VALUE=DATE-TIME:20240222T154000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-606@indico.ecap.work
DESCRIPTION:Speakers: Luca Marchetti (University of New Brunswick)\nA majo
r challenge at the interface between quantum gravity and cosmology is to u
nderstand how cosmological structures can emerge from physics at the Planc
k scale. In this talk\, I will provide a concrete example of such an emerg
ence process by extracting the physics of scalar and isotropic cosmologica
l perturbations from full quantum gravity\, as described by a causally com
plete Barrett-Crane group field theory model. From the perspective of the
underlying quantum gravity theory\, cosmological perturbations will be ass
ociated with (relational) nearest-neighbor two-body entanglement\, providi
ng crucial insights into the potentially purely quantum-gravitational natu
re of cosmological perturbations. I will also show that at low energies th
e emergent relational dynamics of these perturbations are perfectly consis
tent with those of general relativity\, while at trans-Planckian scales qu
antum effects become important. Finally\, I will comment on the implicatio
ns of these quantum effects for the physics of the early universe and outl
ine future research directions.\n\nhttps://indico.ecap.work/event/67/contr
ibutions/606/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/606/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Primordial Black Holes and Loop Quantum Gravity
DTSTART;VALUE=DATE-TIME:20240223T143000Z
DTEND;VALUE=DATE-TIME:20240223T151500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-639@indico.ecap.work
DESCRIPTION:Speakers: Francesca Vidotto ()\nPrimordial black holes have gr
own in popularity as a dark matter candidate. Different mass spectrum for
them are currently under consideration. In this talk I discuss how Loop Q
uantum Cosmology can integrate the presence of primordial black holes\, ei
ther in an inflationary scenario or in a ekpyrotic scenario. I review some
recent results and discuss the current work in progress. I focus in parti
cular on the possibility of primordial black holes being in the form of bl
ack holes remnants: I review the process of creating the remnants from a b
lack-to-while hole transition and the phenomenology associated to them as
dark matter.\n\nhttps://indico.ecap.work/event/67/contributions/639/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/639/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Black Hole Remnants and White Holes
DTSTART;VALUE=DATE-TIME:20240219T131500Z
DTEND;VALUE=DATE-TIME:20240219T140000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-638@indico.ecap.work
DESCRIPTION:Speakers: Carlo Rovelli (Aix-Marseille University)\nI summariz
e my current understanding of what LQG indicates about what happens where
classical GR fails in realistic black holes.\n\nhttps://indico.ecap.work/e
vent/67/contributions/638/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/638/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spin foam amplitude of the black-to-white hole transition
DTSTART;VALUE=DATE-TIME:20240223T151500Z
DTEND;VALUE=DATE-TIME:20240223T160000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-636@indico.ecap.work
DESCRIPTION:Speakers: Cong Zhang ()\nAt the end of Hawking evaporation\, a
s the black hole horizon approaches the Planck scale\, the effects of quan
tum gravity become significant. Based on the conjecture that these quantum
gravity effects may induce the transition of the black hole into a white
hole\, this transition amplitude is studied within the framework of the sp
in foam model.\n\nThe spin foam amplitude is built on a 2-complex containi
ng 56 vertices. The boundary state in the amplitude is selected as the Thi
emann's complexifier coherent state resembling the semiclassical geometry.
Taking into account the fact that triad fields of different orientations\
, i.e.\, $e_i^a$ and $-e_i^a$\, give the same intrinsic geometry of the bo
undary\, we creatively adopt the the boundary state as the superposition o
f the coherent states associated with the both orientations. We employ the
method of complex critical point to numerically compute the transition am
plitude. Despite the numerical results\, it is interestingly found that th
e transition amplitude is dominated by the terms allowing the change in or
ientation. This finding suggests that the black-to-white hole transition s
hould be accompanied by the tunneling process of a change in orientation.\
n\nhttps://indico.ecap.work/event/67/contributions/636/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/636/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entanglement and Quantum Geometry
DTSTART;VALUE=DATE-TIME:20240222T131500Z
DTEND;VALUE=DATE-TIME:20240222T140000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-635@indico.ecap.work
DESCRIPTION:Speakers: Eugenio Bianchi (Penn State)\nWe discuss how the ent
anglement entropy of geometric observables provides a probe of locality an
d semiclassicality in loop quantum gravity. We use the quantum polyhedron
and intertwiner space as a model system that allows us to illustrate concr
etely this connection.\n\nhttps://indico.ecap.work/event/67/contributions/
635/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/635/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carroll and Galilei limits of 3D and 4D ($\\Lambda$-)BMS symmetrie
s
DTSTART;VALUE=DATE-TIME:20240220T163500Z
DTEND;VALUE=DATE-TIME:20240220T170000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-633@indico.ecap.work
DESCRIPTION:Speakers: Tomasz Trześniewski (University of Wroclaw)\nThere
are two threads in the research on symmetries of space-time that originate
d in the 1960s but have been reinvigorated by the increased interest over
the past few years: BMS symmetry (later extended by Barnich and Troessaert
) and the kinematical symmetries other than Poincare or (anti-)de Sitter (
especially the Carroll and Galilei ones). At their intersection\, one may
consider the Carrollian and Galilean contraction limits of BMS algebras. I
t turns out that we can consistently define such contractions for 3D BMS a
nd (partially) 3D $\\Lambda$-BMS algebras\, while in the case of 4D BMS (i
n the sense of Barnich and Troessaert) we only obtain quasi-Carrollian/Gal
ilean BMS algebras. This can be compared with the recent studies of contra
ctions of the original BMS algebra\, in which their authors came to quite
different conclusions. Furthermore\, in the context of quantum gravity\, q
uantum-group deformations are being generalized to both BMS and various ki
nematical algebras and hence it should be worthy to also analyze the inter
play between the deformations of BMS algebras and their Carrollian or Gali
lean contractions.\n\nhttps://indico.ecap.work/event/67/contributions/633/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/633/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum geometry\, knots\, quivers\, and lattice paths
DTSTART;VALUE=DATE-TIME:20240221T131500Z
DTEND;VALUE=DATE-TIME:20240221T140000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-632@indico.ecap.work
DESCRIPTION:Speakers: Piotr Sułkowski (University of Warsaw)\nI will disc
uss how quantum geometry is associated to ensembles of lattice paths\, how
it captures properties of quiver moduli spaces\, and at the same time enc
odes invariants of knots. Relations between these seemingly unrelated topi
cs arise from dualities in topological string theory and appropriately eng
ineered systems of branes.\n\nhttps://indico.ecap.work/event/67/contributi
ons/632/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/632/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Axial Scalar Perturbations in Kantowski-Sachs Spacetimes
DTSTART;VALUE=DATE-TIME:20240219T165500Z
DTEND;VALUE=DATE-TIME:20240219T172000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-628@indico.ecap.work
DESCRIPTION:Speakers: Andrés Mínguez-Sánchez (Instituto de Estructura d
e la Materia - CSIC)\nRecently\, there has been a growing interest in inve
stigating homogeneous but anisotropic spacetimes due to their relation wit
h non-rotating\, uncharged black hole interiors. We present a description
of axial perturbations for a massless scalar field minimally coupled to th
is geometry. We truncate the action at the quadratic perturbative order an
d tailor our analysis to compact spatial sections. Perturbations are descr
ibed in terms of perturbative gauge invariants\, linear perturbative const
raints\, and their canonically conjugate variables. The entire set\, encom
passing perturbations and homogeneous degrees of freedom\, is completed in
to a canonical one. We employ a hybrid quantization framework\, composing
a quantum representation of the homogeneous sector using Loop Quantum Cosm
ology techniques with a conventional field quantization of the perturbatio
ns.\n\nhttps://indico.ecap.work/event/67/contributions/628/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/628/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Entangled pairs in evaporating black holes
DTSTART;VALUE=DATE-TIME:20240222T123000Z
DTEND;VALUE=DATE-TIME:20240222T131500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-627@indico.ecap.work
DESCRIPTION:Speakers: Beatriz Elizaga Navascues (Louisiana State Universit
y)\nIn this talk we present a QFT study about the entanglement structure o
f the Hawking effect in evaporating scenarios. For this purpose\, first we
review the known concept of Hawking partners\, as being the field modes t
hat are entangled with\, and thus purify\, the thermal radiation. Then\, w
e show how the definition of these partners can be generalized to any case
where the temperature of the radiation increases over time according to t
he semiclassical evaporation process. Our explicit computation allows us t
o study the relative location of radiation and partner modes at past null
infinity. Finally\, we discuss some physical consequences of our results o
n the fate of quantum information in gravitational collapse.\n\nhttps://in
dico.ecap.work/event/67/contributions/627/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/627/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lessons from DLCQ for physics at null infinity
DTSTART;VALUE=DATE-TIME:20240220T123000Z
DTEND;VALUE=DATE-TIME:20240220T131500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-624@indico.ecap.work
DESCRIPTION:Speakers: Glenn Barnich (Université libre de Bruxelles)\nMoti
vated by issues in the context of asymptotically flat spacetimes at null i
nfinity\, we clarify in the simplest example of a massless scalar field in
two dimensions several subtleties that arise when setting up the canonica
l formulation on a single or on two intersecting null hypersurfaces with a
special emphasis on the infinite-dimensional global and conformal symmetr
ies\, the free data\, a consistent treatment of zero modes\, matching con
ditions\, implications for quantization of massless versus massive fields.
\n\nhttps://indico.ecap.work/event/67/contributions/624/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/624/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gravitationally induced decoherence of single particles
DTSTART;VALUE=DATE-TIME:20240221T151500Z
DTEND;VALUE=DATE-TIME:20240221T154000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-623@indico.ecap.work
DESCRIPTION:Speakers: Max Joseph Fahn (Institute for Quantum Gravity\, Erl
angen)\nBy combining the techniques of open quantum systems with GR\, it i
s possible to derive an evolution equation\, usually called master equatio
n\, that predicts the effective dynamics of a matter system under the infl
uence of gravity\, where the latter is treated as environment. In the talk
\, the master equation derived in arXiv:2206.06397 for gravitationally ind
uced decoherence of a scalar field using Ashtekar variables is applied to
the one-particle sector\, motivated by the prospect of measuring similar d
ecoherence effects in astroparticles such as neutrinos. Here\, we will pre
sent the steps required to extract the effective dynamics of a single scal
ar particle from the field-theoretic master equation: After a projection t
o the single particle space\, the resulting evolution equation is connecte
d to Feynman diagrams through which the underlying field theory of lineari
sed gravity coupled to a scalar field can be interpreted as an effective f
ield theory. Making use of this link\, a UV renormalisation is sketched. I
n a final step\, different approximations that cast the master equation in
to a completely positive one are compared\, the resulting decoherence of t
he single scalar particle is analysed\, and possible applications are disc
ussed.\n\nhttps://indico.ecap.work/event/67/contributions/623/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/623/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Why does LIGO have a new 300-meter cavity?
DTSTART;VALUE=DATE-TIME:20240221T170000Z
DTEND;VALUE=DATE-TIME:20240221T172500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-622@indico.ecap.work
DESCRIPTION:Speakers: Jorge Pullin (LSU)\nWe discuss the role of the new c
avity in the LIGO interferometers to address the issue of the quantum nois
e in the instruments.\n\nhttps://indico.ecap.work/event/67/contributions/6
22/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/622/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Superposition of Spacetimes in the Laboratory
DTSTART;VALUE=DATE-TIME:20240220T170000Z
DTEND;VALUE=DATE-TIME:20240220T172500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-621@indico.ecap.work
DESCRIPTION:Speakers: Ofek Bengyat (IQOQI Vienna)\nI will present [O. Beng
yat\, A. Di Biagio\, M. Christodoulou\, M. Aspelmeyer\, arXiv:2309.16312\,
submitted to PRL]\, where we argue for the equivalence between (i) an exp
erimentally relevant Gravity Induced Entanglement (GIE) experiment and (ii
) the original one\, which is much less feasible and would require impleme
ntation in space. The original one comprises the interaction of two partic
les prepared in a superposition of two discrete paths [Bose et al\, Phys.
Rev. Lett. 119\, 240401]\, [Marletto & Vedral Phys. Rev. Lett. 119\, 24040
2]. The feasible one comprises a continuously delocalized (harmonic oscill
ator) state of motion [Krisnanda et al\, npj Quantum Information 6\, 12 (2
020)]. An important open question has been whether these two different app
roaches allow to draw the same conclusions on the quantum nature of gravit
y. To answer this question\, we use a path-integral approach to analyse a
setup that contains both features: a superposition of two highly delocaliz
ed center of mass states. In both cases the appearance of entanglement\, w
ithin linearised quantum gravity\, is due to gravity being in a superposit
ion of distinct geometries. Moreover\, we are able to calculate the relati
vistic corrections to the entanglement. An experimental detection of those
would be evidence for participation of both radiative and non-radiative d
egrees of freedom in GIE. This contributes to the debate around the matter
\, as the radiative degrees of freedom are considered the only ones releva
nt in the eyes of some [Anastopoulos et al\, arXiv:2103.08044].\n\nhttps:/
/indico.ecap.work/event/67/contributions/621/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/621/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Curvature from internal spacetime geometry
DTSTART;VALUE=DATE-TIME:20240221T154000Z
DTEND;VALUE=DATE-TIME:20240221T160500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-619@indico.ecap.work
DESCRIPTION:Speakers: Charlie Beil (University of Graz)\nInternal spacetim
e geometry was recently introduced with the aim of modeling quantum nonloc
ality using degenerate spacetime metrics. Such a spacetime is equipped wit
h a set of worldlines for which time is stationary\, that is\, worldlines
with no interior points. Consequently\, the dimensions of tangent spaces v
ary at points where these worldlines intersect\, and a projective measurem
ent of spin or polarization corresponds to an actual projection between ta
ngent spaces of different dimensions. Moreover\, the standard model partic
les can be decomposed into particles with such worldlines using the Dirac
Lagrangian. In this talk I will give an overview of this geometric framewo
rk\, and show how spacetime curvature naturally arises.\n\nhttps://indico.
ecap.work/event/67/contributions/619/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/619/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spherical collapse and black hole evaporation
DTSTART;VALUE=DATE-TIME:20240219T151500Z
DTEND;VALUE=DATE-TIME:20240219T160000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-617@indico.ecap.work
DESCRIPTION:Speakers: Madhavan Varadarajan (Raman Research Institute)\nhtt
ps://indico.ecap.work/event/67/contributions/617/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/617/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Subleading structure of asymptotically-flat spacetimes
DTSTART;VALUE=DATE-TIME:20240220T131500Z
DTEND;VALUE=DATE-TIME:20240220T140000Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-616@indico.ecap.work
DESCRIPTION:Speakers: Marc Geiller (ENS de Lyon)\nTBA\n\nhttps://indico.ec
ap.work/event/67/contributions/616/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/616/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Solving the problem of time in terms of Dirac observables
DTSTART;VALUE=DATE-TIME:20240219T123000Z
DTEND;VALUE=DATE-TIME:20240219T131500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-615@indico.ecap.work
DESCRIPTION:Speakers: Jorge Pullin (LSU)\nWe argue that combining Rovelli'
s evolving constants of the motion with Page and Wootters relational appro
ach solves the issues both approaches face and provides a way of addressin
g the problem of time in terms of Dirac observables. As a bonus it also al
lows to tackle the problem of time of arrival in quantum mechanics. The fr
amework is compatible with the approach in terms of POVM's of Hoehn et al.
introduced recently.\n\nhttps://indico.ecap.work/event/67/contributions/6
15/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/615/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Reviving Quantum Geometrodynamics
DTSTART;VALUE=DATE-TIME:20240223T123000Z
DTEND;VALUE=DATE-TIME:20240223T131500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-614@indico.ecap.work
DESCRIPTION:Speakers: Susanne Schander (Perimeter Institute)\nQuantum Geom
etrodynamics represents an early attempt at the canonical quantization of
General Relativity. In a seminal paper\, DeWitt proposed a formal Hamilton
ian constraint operator by substituting canonical momenta with variational
derivative operators. However\, the rigorous interpretation of this opera
tor has remained elusive due to the highly nonlinear nature of the constra
int and the associated issues arising from the multiplication of distribut
ions. Consequently\, a well-defined Hilbert space for the theory could not
be specified. In this talk\, we propose a novel approach to overcome the
difficulties faced by Quantum Geometrodynamics. We employ a lattice discr
etization that adheres as closely as possible to the original formulation\
, and examine the lattice corrections to the theory. We discuss the steps
necessary for obtaining a well-defined continuum limit and explain how to
perform calculations in the effective theory.\n\nMoreover\, we establish H
ilbert spaces for the lattice theories that allow for well-defined lattice
approximations of all continuum quantities. These Hilbert spaces exhibit
a non-standard representation of the canonical commutation relations betw
een the matrix elements of the spatial metric and the conjugate momenta. T
his approach ensures that states are exclusively supported on positive def
inite symmetric matrices.\n\nhttps://indico.ecap.work/event/67/contributio
ns/614/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/614/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gravitationally induced decoherence models for different matter sy
stems and their applications
DTSTART;VALUE=DATE-TIME:20240221T143000Z
DTEND;VALUE=DATE-TIME:20240221T151500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-612@indico.ecap.work
DESCRIPTION:Speakers: Kristina Giesel (FAU)\nIn this talk we consider ope
n quantum systems in which either a scalar field or photons are coupled to
linearised gravity. We compare the derivation of the corresponding effect
ive dynamics of the matter systems\, encoded in a so-called master equatio
n\, in a reduced phase space quantisation\, and discuss the similarities a
nd differences of the two models. Finally\, we discuss possible applicatio
ns of these models with special emphasis on the comparison with existing p
henomenological models.\n\nhttps://indico.ecap.work/event/67/contributions
/612/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/612/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum equivalence principle and de-Sitter space
DTSTART;VALUE=DATE-TIME:20240220T143000Z
DTEND;VALUE=DATE-TIME:20240220T151500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-610@indico.ecap.work
DESCRIPTION:Speakers: Maciej Dunajski (University of Cambridge)\nI discuss
the impact of the positive cosmological constant on the interplay between
the equivalence principle in general relativity\, and the rules of quantu
m mechanics. At the nonrelativistic level\, there is an ambiguity in the d
efinition of a phase of a wave function measured by inertial and accelerat
ing observes. This is the cosmological analogue of the Penrose effect\, wh
ich can also be seen as a nonrelativistic limit of the Unruh effect.\n\nht
tps://indico.ecap.work/event/67/contributions/610/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/610/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Second Order Geometry and the Quantum Foam
DTSTART;VALUE=DATE-TIME:20240223T172000Z
DTEND;VALUE=DATE-TIME:20240223T174500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-608@indico.ecap.work
DESCRIPTION:Speakers: Folkert Kuipers (LMU Munich)\nThe search for a theor
y that consistently combines quantum theory with general relativity forces
us to consider geometrical frameworks beyond standard (first order) diffe
rential geometry. One candidate for such a generalized geometrical framewo
rk is second order (stochastic) differential geometry\, which incorporates
a violation of Leibniz rule\, that is characteristic to the Wiener integr
al\, into the geometry. This feature makes the framework an ideal tool in
the study of covariant path integrals.\nIn this talk\, I will review the b
asic ingredients of this framework in both a Euclidean and Lorentzian sign
ature. I will pay particular attention to the deformations of spacetime sy
mmetries that arise due to the coupling of spacetime fluctuations to the a
ffine connection\, and discuss some connections to non-commutative geometr
y.\n\nhttps://indico.ecap.work/event/67/contributions/608/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/608/
END:VEVENT
BEGIN:VEVENT
SUMMARY:From perturbative algebraic QFT to QG
DTSTART;VALUE=DATE-TIME:20240221T123000Z
DTEND;VALUE=DATE-TIME:20240221T131500Z
DTSTAMP;VALUE=DATE-TIME:20240625T021454Z
UID:indico-contribution-67-605@indico.ecap.work
DESCRIPTION:Speakers: Kasia Rejzner (University of York)\nIn this talk\, I
will demonstrate how methods of (perturbative) algebraic quantum field th
eory can be applied to certain problems in quantum gravity. I will focus o
n three aspects: asymptotic safety\, diffeomorphism invariant relational o
bservables\, fundamental discreteness as a UV regulator for QFT.\n\nhttps:
//indico.ecap.work/event/67/contributions/605/
LOCATION:
URL:https://indico.ecap.work/event/67/contributions/605/
END:VEVENT
END:VCALENDAR