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BEGIN:VEVENT
SUMMARY:Physics with non-perturbative quantum gravity: the end of the Hawk
ing evaporation
DTSTART:20230512T130000Z
DTEND:20230512T134500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-648@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Carlo Rovelli (Centre de Physique Théorique (CPT))\
n\nQuantum gravitational phenomena dominate the physics of a black hole in
the past of a high curvature spacelike surface. Because of the backreacti
on of the evaporation\, this surface crosses the horizon. I describe a re
cent line of investigation on the possible evolution compatible with nonp
erturbative quantum gravity\, and in particular I illustrate what can be p
redicted using loop quantum gravity.\n\nhttps://events.perimeterinstitute.
ca/event/39/contributions/648/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/648/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum Gravity and its connection to observations
DTSTART:20230508T133000Z
DTEND:20230508T141500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-621@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Astrid Eichhorn (University of Southern Denmark)\n\n
To make progress in developing a quantum theory of gravity\, we need to co
nnect candidate theories to observations. I will review ideas on connectin
g quantum gravity to observations in particle physics\, to searches for da
rk matter and to observations of black holes\, in particular with the (nex
t-generation) Event Horizon Telescope.\n\nhttps://events.perimeterinstitut
e.ca/event/39/contributions/621/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/621/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Looking for Echoes from Quantum Black Holes
DTSTART:20230511T134500Z
DTEND:20230511T143000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-642@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Jahed Abedi (University of Stavanger)\n\nI present a
n unprecedented template-based search for stimulated emission of Hawking r
adiation (or Boltzmann echoes) by combining the gravitational wave data fr
om 65 binary black hole merger events observed by the LIGO/Virgo collabora
tion. With a careful Bayesian inference approach\, I found no statisticall
y significant evidence for this signal in either of the 3 Gravitational Wa
ve Transient Catalogs GWTC-1\, GWTC-2 and GWTC-3. However\, the data canno
t yet conclusively rule out the presence of Boltzmann echoes either\, with
the Bayesian evidence ranging within 0.3-1.6 for most events\, and a comm
on (non-vanishing) echo amplitude for all mergers being disfavoured at onl
y 2:5 odds. The only exception is GW190521\, the most massive and confiden
tly detected event ever observed\, which shows a positive evidence of 9.2
for stimulated Hawking radiation. An optimal combination of posteriors yie
lds an upper limit of A\n\nhttps://events.perimeterinstitute.ca/event/39/c
ontributions/642/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/642/
END:VEVENT
BEGIN:VEVENT
SUMMARY:What is the simplicity of the early universe trying to tell us?
DTSTART:20230508T180000Z
DTEND:20230508T184500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-624@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Latham Boyle (Perimeter Institute)\n\n"After reviewi
ng some key hints and puzzles from the early\nuniverse\, I will introduce
recent joint work with Neil Turok\nsuggesting a rigid and predictive new a
pproach to addressing them.\n\nOur universe seems to be dominated by radia
tion at early times\, and positive vacuum energy at late times. Taking th
e symmetry and analyticity properties of such a spacetime seriously leads
to a new formula for the gravitational entropy of our universe\, and a pic
ture in which the Big Bang may be regarded as a kind of mirror.\n\nI will
explain how this line of thought suggests new explanations for a number of
observed properties of the universe\, including: its homogeneity\, isotro
py and flatness\; the arrow of time (i.e. the fact that entropy increases
*away* from the bang)\; several properties of the primordial perturbations
\; the nature of dark matter (which\, in this picture\, is a right-handed
neutrino\, radiated from the early universe like Hawking radiation from a
black hole)\; the origin of the\nprimordial perturbations\; and even the e
xistence of three generations of standard model fermions. I will discuss
some observational predictions that will be tested in the coming decade\,
and some key open questions."\n\nhttps://events.perimeterinstitute.ca/even
t/39/contributions/624/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/624/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Where effective field theory fails: Windows into quantum gravity?
DTSTART:20230509T134500Z
DTEND:20230509T143000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-628@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Adam Koberinski (University of Pittsburgh)\n\nEffect
ive field theory is a computationally powerful and flexible theoretical fr
amework\, finding application in many areas of physics. In particle physic
s\, Weinberg’s folk theorem also promises that any theory that reproduce
s the predictions of the Standard Model will\, at low energies\, look like
an effective field theory. In one sense the power of this framework shoul
d be a cause for pride in the progress of physics and discovery of real st
ructural features of the world. But given the inability to fully unite qua
ntum theory and gravity into a consistent theoretical picture\, there is a
lso cause for pessimism: indirect tests of candidate theories of quantum g
ravity will ultimately reduce to something like an effective field theory\
, undermining efforts to find low-energy windows into new physics. One way
around this pessimism is to look at where and why effective field theory
breaks down in current physical theories. I will point to familiar breakdo
wns (the cosmological constant\, inflation\, the hierarchy problem)\, offe
ring a take on what these breakdowns tell us about the shape of physics be
yond the Standard Model. Cracks in the wall of effective field theory allo
w for a dim glimpse of what might lie beyond.\n\nhttps://events.perimeteri
nstitute.ca/event/39/contributions/628/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/628/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nonlocality in the causal set approach to quantum gravity
DTSTART:20230511T180000Z
DTEND:20230511T184500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-645@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Fay Dowker (Imperial College London)\n\nThe nonlocal
ity of causal sets gives us hope of solving the cosmological constant puzz
le (``why is the universe so smooth\, big and old if there is only one sca
le---the discreteness scale---in the theory?’’)\n\nOn the other hand l
ocality\, \, GR and local QFT\, must be recovered from quantum gravity in
the continuum approximation at large scales\, which is a challenge. If w
e are lucky though (like Goldilocks\, the universe gets the nonlocality ``
just right’’) nonlocality may be a rich source of phenomenology. Yasam
an Yazdi’s talk will be on cosmological models based on the nonlocality
of causal sets. I will give a couple of examples of more astrophysical phe
nomenological models based on simple assumptions---randomness due to space
time uncertainty and Lorentz invariance---and pose a research question: is
there a model of ``quantum swerves’’?\n\nhttps://events.perimeterinst
itute.ca/event/39/contributions/645/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/645/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum Superpositions of Black Holes
DTSTART:20230510T154500Z
DTEND:20230510T163000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-637@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Robert Mann (University of Waterloo)\n\nIf relativis
tic gravitation has a quantum description\, it must be meaningful to consi
der a spacetime metric in a genuine quantum superposition. Here I present
a new operational framework for studying “superpositions of spacetimes
” via model particle detectors. After presenting the general approach\,
I show how it can be applied to describe a spacetime generated by a BTZ
black hole in a superposition of masses and how such detectors would respo
nd. The detector exhibits signatures of quantum-gravitational effects rem
iniscent of Bekenstein’s seminal conjecture concerning the quantized mas
s spectrum of black holes in quantum gravity. I provide further remarks
in distinguishing spacetime superpositions that are genuinely quantum-grav
itational\, notably with reference to recent proposals to test gravitatio
nally-induced entanglement\, and those in which a putative superposition c
an be re-expressed in terms of dynamics on a single\, fixed spacetime back
ground.\n\nhttps://events.perimeterinstitute.ca/event/39/contributions/637
/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/637/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The emergence of spacetime is governed by a quantum Mach's princip
le
DTSTART:20230512T154500Z
DTEND:20230512T163000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-651@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Lee Smolin (Perimeter Institute)\n\n"I describe a ca
ndidate for a fundamental physical theory called the causal theory of view
s. This describes a world constructed by a continual creation of events\;
where an event is a transition at which a small portion of the possible\
nbecomes actual. I first recall older results which includes the emergenc
e of space and\, with space\, a non-relativistic N-body quantum dynamics.
I next describe recent progress on this model including\, in a different
limit\, a formulation of a cut off quantum field theory\, which we descr
ibe in terms of an S-Matrix formulation of amplitudes. \n\nThe dynamics i
s specified by an action principle consisting of a kinetic energy and pote
ntial energy term. \nThe former are based on measures of how quickly comp
onents of causal change do so with respect to averaged notions. The poten
tial energy terms measure how much local moves alter an observer's ""view"
" of the universe\, as seen from their perspective.\n\nThese results show
that quantum dynamics is restored in an N to infinity limit. Measurable n
on-linear corrections to quantum dynamics emerge to higher order in 1/sqrt
{N}. "\n\nhttps://events.perimeterinstitute.ca/event/39/contributions/651
/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/651/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Do First-Class Constraints Generate Gauge Transformations? A Geome
tric Perspective.
DTSTART:20230510T150000Z
DTEND:20230510T154500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-636@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Clara Bradley (University of California\, Irvine)\n\
nThe constrained Hamiltonian formalism is the basis for canonical quantiza
tion techniques. However\, there are disagreements surrounding the notion
of a gauge transformation in such a formalism. The standard definition of
a gauge transformation in the constrained Hamiltonian formalism traces bac
k to Dirac: a gauge transformation is a transformation generated by an arb
itrary combination of first-class constraints. On the basis of this defini
tion\, Dirac argued that one should extend the form of the Hamiltonian in
order to include all of the gauge freedom. However\, Pitts (2014) argues t
hat in some cases\, a first-class constraint does not generate a gauge tra
nsformation\, but rather "a bad physical change". Similarly\, Pons (2005)
argues that Dirac's analysis of gauge transformations is "incomplete" and
does not provide an account of the symmetries between solutions. Both auth
ors conclude that extending the Hamiltonian in the way suggested by Dirac
is unmotivated. If correct\, these arguments could have implications for o
ther issues in the foundations of the constrained Hamiltonian formalism\,
including the Problem of Time. In this talk\, I use a geometric formulatio
n of the constrained Hamiltonian formalism to show that one can motivate t
he extension to the Hamiltonian independently from consideration of the ga
uge transformations\, and I argue that this supports the standard definiti
on of a gauge transformation without falling prey to the criticisms of Pit
ts (2014) and Pons (2005). Therefore\, in order to maintain that first-cla
ss constraints do not generate gauge transformations\, one must reject the
claim that the constrained Hamiltonian formalism is fully described by th
e geometric picture\; I suggest two avenues for doing so.\n\nhttps://event
s.perimeterinstitute.ca/event/39/contributions/636/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/636/
END:VEVENT
BEGIN:VEVENT
SUMMARY:In Search of Lost Spacetime
DTSTART:20230510T180000Z
DTEND:20230510T190000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-638@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Chris Smeenk (Western University)\n\nThe classical s
pacetime manifold of general relativity disappears in quantum gravity\, wi
th different research programs suggesting a variety of alternatives in its
place. As an illustration of how philosophers might contribute to an inte
rdisciplinary project in quantum gravity\, I will give an overview of rece
nt philosophical debates regarding how classical spacetime "emerges." I w
ill criticize some philosophers as granting too much weight to the intuiti
on that a coherent physical theory must describe objects as located in spa
ce and time. I will further argue\, based in part on historical episodes\
, that an account of emergence needs to recover the structural features of
classical GR responsible for its empirical success. This is more demandi
ng than it might at first appear\, although the details of recovery will d
iffer significantly among different approaches to quantum gravity.\n\nhttp
s://events.perimeterinstitute.ca/event/39/contributions/638/
LOCATION:PI/1-100 - Theatre (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/638/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Spacetime of Acceleration
DTSTART:20230508T153000Z
DTEND:20230508T161500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-623@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Ruth Gregory (King's College\, London)\n\nI will rev
iew recent work on accelerating spacetimes in 3D\, explaining how accelera
tion manifests for point particles and BTZ black holes\, as well as a nove
l BTZ-like solution in a disconnect region of parameter space. I will also
discuss some holographic aspects of the solutions.\n\nhttps://events.peri
meterinstitute.ca/event/39/contributions/623/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/623/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Welcome and Opening Remarks
DTSTART:20230508T131500Z
DTEND:20230508T133000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-620@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Niayesh Afshordi (University of Waterloo & Perimeter
Institute)\n\nhttps://events.perimeterinstitute.ca/event/39/contributions
/620/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/620/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Conversations & controversies in the early universe
DTSTART:20230509T184500Z
DTEND:20230509T193000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-632@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Phil Halper (Independent)\n\nFor the last ten years
I have been documenting various scenarios for the early universe in a You
Tube series called ‘Before the Big Bang”. Having interviewed many of t
he leader figures of the field including Stephen Hawking\, Roger Penrose\,
Alan Guth (and hosted debates between them)\, this will be a broad survey
of inflation\, it’s suggested prequels and alternatives. I shall highli
ght the strengths and weaknesses of the various proposals and give an insi
de track of the claims and counter claims in attempts to move beyond the s
tandard Big Bang model.\n\nhttps://events.perimeterinstitute.ca/event/39/c
ontributions/632/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/632/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panel Discussion II: Do we need Quantum Gravity to crack the Big B
ang? What about inflation? fact or fiction?
DTSTART:20230509T200000Z
DTEND:20230509T210000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-633@events.perimeterinstitute.ca
DESCRIPTION:https://events.perimeterinstitute.ca/event/39/contributions/63
3/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/633/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Universality of black hole thermodynamics
DTSTART:20230510T130000Z
DTEND:20230510T134500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-634@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Samir Mathur (Ohio State University)\n\nhttps://even
ts.perimeterinstitute.ca/event/39/contributions/634/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/634/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Are we considering enough? Inclusivity in Quantum Gravity and Cosm
ology
DTSTART:20230508T184500Z
DTEND:20230508T193000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-625@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Jarita Holbrook (University of Edinburgh)\n\nhttps:/
/events.perimeterinstitute.ca/event/39/contributions/625/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/625/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Causality at the End-of-World
DTSTART:20230510T134500Z
DTEND:20230510T143000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-635@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Beni Yoshida (Perimeter Institute)\n\nThe success of
the AdS/CFT correspondence motivates a holographic approach for spacetime
beyond AdS\, including our own universe. One possible method involves usi
ng an asymptotically-AdS holography and introducing a finite radial cutoff
by inserting an End-of-World (EoW) brane. However\, previous studies have
shown that this leads to nonlocal effects on the boundary and violates en
tanglement sub-additivity. In this work\, we address these issues by exami
ning a two-particle scattering process through the lens of holographic qua
ntum tasks. Our findings suggest that connectedness of entanglement wedge
does indeed require nonlocal domain of dependence\, but that violation of
sub-additivity can be avoided. We also discuss an important question that
arises from our results\, namely whether the non-locality on the EoW brane
is real or apparent. We argue that it is the latter. This talk is based o
n ongoing work with Takato Mori.\n\nhttps://events.perimeterinstitute.ca/e
vent/39/contributions/635/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/635/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panel Discussion I: Where and when will Quantum Gravity crack? Wha
t are we missing?
DTSTART:20230508T200000Z
DTEND:20230508T210000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-626@events.perimeterinstitute.ca
DESCRIPTION:https://events.perimeterinstitute.ca/event/39/contributions/62
6/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/626/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Final but Incomplete?
DTSTART:20230509T154500Z
DTEND:20230509T163000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-630@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Richard Dawid (Stockholm University)\n\nString theor
y has not come close to a complete formulation after half a century of int
ense research. On the other hand\, a number of features of the theory sugg
est that the theory in its complete form may be a final theory. The combin
ation of conceptual incompleteness and allusions to finality seems difficu
lt to grasp. Two main points are made in this talk. First\, it is pointed
out that finality claims in the context of string theory are motivated in
a fundamentally different way than traditional claims of finality one find
s in earlier physics. Second\, it is argued that finality and chronic conc
eptual incompleteness may be related to each other in a string theory cont
ext in an interesting way. The talk ends with discussing possible implicat
ions of this situation for the long-term prospects of theory building in f
undamental physics.\n\nhttps://events.perimeterinstitute.ca/event/39/contr
ibutions/630/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/630/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The role of singularities in the search for quantum gravity
DTSTART:20230509T180000Z
DTEND:20230509T184500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-631@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Karen Crowther (University of Oslo)\n\nSingularities
in general relativity and quantum field theory are often taken not only t
o motivate the search for a more-fundamental theory (quantum gravity)\, bu
t also to characterise this new theory and shape expectations of what it i
s to achieve. In this talk\, I will explore how different types of singula
rities play a role in the search for quantum gravity\, and how different `
attitudes' towards singularities can lead to different scenarios for the n
ew theory. [Based on joint work with Sebastian DeHaro].\n\nhttps://events.
perimeterinstitute.ca/event/39/contributions/631/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/631/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Holographic Cosmology
DTSTART:20230510T193000Z
DTEND:20230510T201500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-639@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Paul McFadden (Newcastle University)\n\nHolography h
as profoundly transformed our understanding of quantum gravity in spacetim
es with asymptotic negative curvature. Its implications for cosmology are
equally profound\, suggesting that time is emergent and that our universe
has a dual description in terms of a three-dimensional quantum field theo
ry. This talk will outline key features of holographic cosmology\, from t
he perspective it offers for the cosmic singularity to the strategies it p
resents for computing cosmological observables. Recent results for the de
Sitter wavefunction will be discussed and their interpretation in the lan
guage of three-dimensional conformal field theory.\n\nhttps://events.perim
eterinstitute.ca/event/39/contributions/639/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/639/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Experimental Cosmology
DTSTART:20230509T150000Z
DTEND:20230509T154500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-629@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Matthew Johnson (Perimeter Institute & York Universi
ty)\n\nhttps://events.perimeterinstitute.ca/event/39/contributions/629/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/629/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panel Discussion IV: UV/IR coupling in Quantum Gravity: Feature or
Bug?[
DTSTART:20230511T200000Z
DTEND:20230511T210000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-647@events.perimeterinstitute.ca
DESCRIPTION:https://events.perimeterinstitute.ca/event/39/contributions/64
7/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/647/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panel Discussion III: Holography: fact or fiction?
DTSTART:20230510T201500Z
DTEND:20230510T210000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-640@events.perimeterinstitute.ca
DESCRIPTION:https://events.perimeterinstitute.ca/event/39/contributions/64
0/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/640/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The H0 tension and sample variance
DTSTART:20230511T150000Z
DTEND:20230511T154500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-643@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Will Percival (University of Waterloo & Perimeter In
stitute)\n\nLocal measurements of the expansion rate of the local universe
differ from predictions of simple models fitted to large-scale cosmologic
al measurements\, at a statistically significant level. Sample variance (o
ften called cosmic variance) is a key component of errors placed on measur
ements made from a small data set. For the Hubble constant\, which paramet
rises the expansion rate\, the size of the patch of the Universe covered b
y recent supernovae observations has a radius of 300Mpc. The smaller the p
atch\, the larger the patch-to-patch fluctuations and the larger the error
on the measured value of H0 from sample variance. Using the H0 measuremen
t from supernovae as an example\, I will consider a number of different wa
ys to estimate sample variance using techniques developed for multiple use
s\, and show that they all approximately agree. The sample variance error
on H0 measurements from the recent Pantheon supernovae sample is +/-1 kms^
-1Mpc^-1\, insufficient to explain the Hubble tension in a standard Lambda
-CDM universe. This will demonstrate methods for comparing variations in e
xpansion rate in the universe and what we mean by saying the universe is e
xpanding (on average)\, or that galaxies move apart with particular veloci
ties.\n\nhttps://events.perimeterinstitute.ca/event/39/contributions/643/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/643/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Everpresent Λ Cosmology
DTSTART:20230511T184500Z
DTEND:20230511T193000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-646@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Yasaman Yazdi (Imperial College London)\n\nI will di
scuss a number of theoretical\, observational\, and conceptual aspects of
the Everpresent Λ cosmological model arising from fundamental principles
in causal set theory and unimodular gravity. In this framework the value o
f the cosmological constant (Λ) fluctuates\, in magnitude and in sign\, o
ver cosmic history. At each epoch\, Λ stays statistically close to the in
verse square root of the spacetime volume. Since the latter is of the orde
r of H^2 today\, this provides a way out of the cosmological constant puzz
le without fine tuning. I will review the theoretical background of this i
dea. I will also describe a phenomenological implementation of this model\
, and discuss recent results on the statistics of its simulations and obse
rvational tests of it.\n\nhttps://events.perimeterinstitute.ca/event/39/co
ntributions/646/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/646/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Analogical reasoning in quantum gravity
DTSTART:20230512T150000Z
DTEND:20230512T154500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-650@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Doreen Fraser (University of Waterloo)\n\nAnalogical
reasoning has a long and distinguished history as a method for making dis
coveries in physics. I will discuss novel uses of formal analogies in twen
tieth century particle physics and condensed matter physics. I will then o
ffer some reflections on how methodological lessons from these cases could
inform the use of analogies in discoveries related to quantum gravity.\n\
nhttps://events.perimeterinstitute.ca/event/39/contributions/650/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/650/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The S8 tension in cosmology
DTSTART:20230511T154500Z
DTEND:20230511T163000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-644@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Mike Hudson (University of Waterloo )\n\nIn additio
n to the now-well known “Hubble tension”\, in recent years a second te
nsion has emerged: the $S_8$ tension. This is a measure of the homogeneity
of the Universe. Specifically\, $S_8$ is defined as $(\\Omega_{\\mathrm m
atter}/0.3)^{0.5} \\sigma_8$ where $\\sigma_8$ is the standard deviation o
f the density fluctuation in an 8 $h^{-1}$ Mpc radius sphere. As with the
Hubble tension\, there is disagreement\, at greater than 4 $\\sigma$ signi
ficance between what is predicted by extrapolating the fluctuations in the
Cosmic Microwave Background forward to the present day\, and what is meas
ured by multiple probes of the inhomogeneity in the nearby Universe. I wil
l discuss the diverse lines of evidence for the tension\, showing it is no
t restricted to one probe\, but is seen in weak gravitational lensing\, pe
culiar velocities and redshift-space distortions and cluster abundances. I
will conclude by discussing prospects for future measurements.\n\nhttps:/
/events.perimeterinstitute.ca/event/39/contributions/644/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/644/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Primordial fluctuations from quantum gravity
DTSTART:20230512T134500Z
DTEND:20230512T143000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-649@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Francesca Vidotto (Western University)\n\nIn modern
cosmology there is an agreement that the seeds of structure formations res
ides in the quantum fluctuation of the geometry in the early universe\, bu
t there is no agreement about how these could be derived from a quantum th
eory of gravity. In this talk I present a proposal based on the covariant
formulation of Loop Quantum Gravity. I describe how to define a wavefuncti
on of the universe in this context\, and a how we can study fluctuations a
nd correlations between spacial regions. The results obtained so far has b
een made possible by recent progress in numerical computations. I discuss
the current state of this research program and the possible implications f
or modeling the early universe.\n\nhttps://events.perimeterinstitute.ca/ev
ent/39/contributions/649/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/649/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Imaging Supermassive Black Holes and mapping spacetime
DTSTART:20230508T141500Z
DTEND:20230508T150000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-622@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Roman Gold (University of Southern Denmark)\n\nI wil
l give an overview of how the Event Horizon Telescope achieves its horizon
scale science and what's to come. I will also review selected recent resu
lts from the Event Horizon Telescope both on Sgr A* and refined analysis o
f M87*. A focus will be on analysis aspects that are relevant for any theo
ry / model building along with a few examples. The presentation aims to pr
ovide key conceptual aspects relevant to gravity experts who are new to VL
BI.\n\nhttps://events.perimeterinstitute.ca/event/39/contributions/622/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/622/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Echoes and Entropy of Quantum Black Holes
DTSTART:20230511T130000Z
DTEND:20230511T134500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-641@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Naritaka Oshita (Kyoto University)\n\nIt has been pr
oposed that quantum-gravitational effects may change the near-horizon stru
cture of black holes\, e.g. firewalls or ultra-compact objects mimicking b
lack holes. Also\, a Lorentz-violating theory as a candidate of quantum gr
avity\, e.g. the Horava-Lifshitz theory\, changes the causal structure of
black holes due to the superluminal propagation of excited modes. The late
-time part of the gravitational wave ringdown from a black hole is signifi
cantly affected by those effects\, and the emission of gravitational wave
echoes may be induced. The black hole quasi-normal (QN) modes are affected
by the change of the horizon structure\, which results in the drastic mod
ification of the late-time signal of the gravitational wave. In this talk\
, I will discuss how the gravitational wave echo can be modeled and how th
e echo model is reasonable from an entropic point of view by counting QN m
odes to estimate the black hole entropy.\n\nhttps://events.perimeterinstit
ute.ca/event/39/contributions/641/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/641/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wrap Up and Discussion: An inclusive roadmap for cracking Quantum
Gravity
DTSTART:20230512T180000Z
DTEND:20230512T193000Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-652@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Steve Weinstein (University of Waterloo)\n\nhttps://
events.perimeterinstitute.ca/event/39/contributions/652/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/652/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emergent Metric Space-Time from the BFSS Matrix Model
DTSTART:20230509T130000Z
DTEND:20230509T134500Z
DTSTAMP:20240424T032700Z
UID:indico-contribution-627@events.perimeterinstitute.ca
DESCRIPTION:Speakers: Robert Brandenberger (McGill University)\n\nEffectiv
e field theory analysis are inadequate to describe the evolution of the ve
ry early universe. I will describe an approach to obtain emergent time\, e
mergent space\, an emergent metric and an emergent early universe cosmolog
y starting from the BFSS matrix model\, a proposed non-perturbative defini
tion of superstring theory. In this approach there is no cosmological cons
tant problem.\n\nhttps://events.perimeterinstitute.ca/event/39/contributio
ns/627/
LOCATION:PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)
URL:https://events.perimeterinstitute.ca/event/39/contributions/627/
END:VEVENT
END:VCALENDAR