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BEGIN:VEVENT
SUMMARY:Scalarized black holes
DTSTART;VALUE=DATE-TIME:20200115T103000Z
DTEND;VALUE=DATE-TIME:20200115T111500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-556@indico.sissa.it
DESCRIPTION:Speakers: Stoytcho Yazadjiev (Sofia University)\, Daniela Done
va (University of Tuebingen)\n\nSpontaneous scalarization is a very intere
sting mechanism endowing the compact object with nontrivial scalar field.
This mechanism is designed to work only in the strong gravity regime while
remaining the weak field regime practically unaltered. While scalarizatio
n was discussed mainly for neutrons stars in the last few decades\, it was
recently discovered that black holes in Gauss-Bonnet gravity can be scala
rized as well with the scalar field sourced by the curvature of the spacet
ime itself that attracted a lot of attention in the field. In the present
talk we will review the main achievements related to scalarized black hole
s starting with the first papers on the subject and paying particular atte
ntion to the recent developments in Gauss-Bonnet gravity and beyond.\n\nht
tps://indico.sissa.it/event/37/contributions/556/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/556/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Importance of the tidal heating in binary coalescence
DTSTART;VALUE=DATE-TIME:20200116T094500Z
DTEND;VALUE=DATE-TIME:20200116T100000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-569@indico.sissa.it
DESCRIPTION:Speakers: Sayak Datta (IUCAA)\n\nWith the observation of the m
ultiple binary inspirals\, we begin to question whether the components of
the binary are black holes or some exotic compact objects (ECO). The black
holeness or the deviation from it can be tested in several ways. The dist
inguishing feature of a black hole from other exotic compact objects is th
e presence of the horizon. This surface acts as a one-way membrane\, that
absorbs energy. Due to this different behavior from ECOs in the late stage
s of an inspiral black holes exchange energy\, these backreact on the orbi
t\, transferring energy and angular momentum from their spin into the orbi
t. This effect is called tidal heating. In Phys.Rev. D99 (2019) no.8\, 084
001 we argued that the tidal heating can be used as a test for the presenc
e of the horizon\, and for that\, we introduced horizon parameter (H). Usi
ng H we showed that in LISA\, presence or absence of the horizon can be te
sted accurately as well as precisely. In arXiv:1910.07841 we compute the o
rbital dephasing and the gravitational-wave signal emitted by a point part
icle in circular\, equatorial motion around a spinning supermassive object
to the leading order in the mass ratio. We showed that the absence of abs
orption by the central object can affect the gravitational-wave signal dra
matically\, especially at high spin. As result it allows us to put an unpa
ralleled upper bound on the reflectivity of exotic compact objects\, at th
e level of O(0.01)%. This can be used even in near\nequal mass binaries to
search for the horizon.\n\nhttps://indico.sissa.it/event/37/contributions
/569/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/569/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Coalescence of Exotic Compact Objects
DTSTART;VALUE=DATE-TIME:20200116T090000Z
DTEND;VALUE=DATE-TIME:20200116T091500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-571@indico.sissa.it
DESCRIPTION:Speakers: Carlos Palenzuela (Universidad de las Islas Baleares
)\, Miguel Bezares (SISSA)\n\nThe direct detection of gravitational waves
(GWs) by the LIGO and VIRGO interferometric detectors has begun a new era
of GW astronomy\, allowing us to study the strong regime of gravity throug
h GW signals produced by coalescence of compact objects. In this talk\, I
will present our numerical studies on coalescence of binary Exotic Compact
Objects (ECOs) performed by solving the Einstein equations with different
types of exotic matter: boson stars\, dark boson stars and Neutron Stars
that contain a small fraction of dark matter particles clustered inside.
These binaries lead to different dynamics and gravitational waves emissio
n during their coalescence\, which might be crucial to distinguish them w
ith current/future LIGO and Virgo observations.\n\nhttps://indico.sissa.it
/event/37/contributions/571/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/571/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Quantum gravity predictions for black hole interior geometry
DTSTART;VALUE=DATE-TIME:20200116T091500Z
DTEND;VALUE=DATE-TIME:20200116T093000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-570@indico.sissa.it
DESCRIPTION:Speakers: Sina Bahrami (Institute for Gravitation and the Cosm
os\, Pennsylvania State University)\, Emanuele Alesci (Institute for Gravi
tation and the Cosmos\, Pennsylvania State University)\, Daniele Pranzetti
(Perimeter Institute)\n\nIn this talk I will show how to derive an effect
ive Hamiltonian constraint for the Schwarzschild geometry starting from th
e full loop quantum gravity Hamiltonian constraint and computing its expec
tation value on coherent states sharply peaked around a spherically symmet
ric geometry. I then use this effective Hamiltonian to study the interior
region of a Schwarzschild black hole\, where a homogeneous foliation is a
vailable. I show how\, for several geometrically and physically well motiv
ated choices of coherent states\, the classical black hole singularity is
replaced by a homogeneous expanding Universe. The resultant geometries hav
e no significant deviations from the classical Schwarzschild geometry in t
he pre-bounce sub-Planckian curvature regime\, evidencing the fact that la
rge quantum effects are avoided in these models. In all cases\, we find no
evidence of a white hole horizon formation. However\, various aspects of
the post-bounce effective geometry depend on the choice of quantum states
and\, in particular\, to the numerical value of the Immirzi parameter.\n\n
https://indico.sissa.it/event/37/contributions/570/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/570/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Post merger signal from black hole mimickers
DTSTART;VALUE=DATE-TIME:20200116T093000Z
DTEND;VALUE=DATE-TIME:20200116T094500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-572@indico.sissa.it
DESCRIPTION:Speakers: Stanislav Babak (APC)\, Alexandre Toubiana (APC/IAP
)\, Luis Lehner (Perimeter Institute)\, Enrico Barausse (SISSA)\n\nBlack h
oles mimickers\, e.g. neutron stars or boson stars\, are compact objects w
ith similar properties to black holes.\nThe gravitational wave signal emit
ted by a binary of such putative objects during the inspiral phase is diff
icult to\ndistinguish from the one emitted by a black hole binary. Neverth
eless\, significant differences might appear in the\npost merger signal.
Inspired by the known behavior of black holes\, neutron stars and boson st
ars we \npropose a toy model that captures potential characteristics of su
ch systems composed by such mimickers. \nThis model can be exploited to as
sess how well such signal could be recovered with gravitational waves obse
rvations from \nearth based detectors using standard templates. By analyzi
ng the residuals\, i.e. the difference between the injected \nsignal and t
he best fit template\, one can also develop strategies to extract the new
physics described by these new signals.\n\nhttps://indico.sissa.it/event/3
7/contributions/572/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/572/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The first image of a black hole
DTSTART;VALUE=DATE-TIME:20200116T103000Z
DTEND;VALUE=DATE-TIME:20200116T111500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-573@indico.sissa.it
DESCRIPTION:Speakers: Luciano Rezzolla\n\nI will briefly discuss how the f
irst image of a black hole was obtained\nby the EHT collaboration. In part
icular\, I will describe the theoretical\naspects that have allowed us to
model the dynamics of the plasma\naccreting onto the black hole and how su
ch dynamics was used to generate\nsynthetic black-hole images. I will also
illustrate how the comparison\nbetween the theoretical images and the obs
ervations has allowed us to\ndeduce the presence of a black hole in M87 an
d to extract information\nabout its properties. Finally\, I will describe
the lessons we have\nlearned about strong-field gravity and alternatives t
o black holes.\n\nhttps://indico.sissa.it/event/37/contributions/573/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/573/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A VISual approach to science communication
DTSTART;VALUE=DATE-TIME:20200116T151500Z
DTEND;VALUE=DATE-TIME:20200116T160000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-575@indico.sissa.it
DESCRIPTION:Speakers: Marcos Valdes\n\nhttps://indico.sissa.it/event/37/co
ntributions/575/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/575/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Opening
DTSTART;VALUE=DATE-TIME:20200114T080000Z
DTEND;VALUE=DATE-TIME:20200114T081500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-541@indico.sissa.it
DESCRIPTION:https://indico.sissa.it/event/37/contributions/541/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/541/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spontaneous scalarization in generalised scalar-tensor theory
DTSTART;VALUE=DATE-TIME:20200115T151500Z
DTEND;VALUE=DATE-TIME:20200115T153000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-566@indico.sissa.it
DESCRIPTION:Speakers: Nicola Franchini (University of Nottingham)\, Giuli
a Ventagli (University of Nottingham)\, Thomas Sotiriou (University of Not
tingham)\, Nikolas Andreou (University of Nottingham)\n\nSpontaneous scala
rization is a mechanism that endows relativistic stars and black holes wit
h a nontrivial configuration only when their spacetime curvature exceeds s
ome threshold. The standard way to trigger spontaneous scalarization is vi
a a tachyonic instability at the linear level\, which is eventually quench
ed due to the effect of non-linear terms. At this work (Phys. Rev. D 99\,
124022 (2019) and arXiv:1904.06365) we identify all of the terms in the Ho
rndeski action that contribute to the (effective) mass term in the lineari
zed equations and\, hence\, can cause or contribute to the tachyonic insta
bility that triggers scalarization. We acknowledge networking support by t
he COST Action GWverse Grant No. CA16104.\n\nhttps://indico.sissa.it/event
/37/contributions/566/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/566/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Detection and parameter estimation for accreting stellar-origin bl
ack-hole binaries and their electromagnetic counterpart
DTSTART;VALUE=DATE-TIME:20200114T093000Z
DTEND;VALUE=DATE-TIME:20200114T094500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-544@indico.sissa.it
DESCRIPTION:Speakers: Sylvain Marsat\, Andrea Caputo\, Enrico Barausse\,
Alexandre Toubiana\, Stanislav Babak\, Laura Sberna (Perimeter Institute)\
, Paolo Pani\n\nWe study the impact of mass accretion in the evolution of
LIGO-like black hole binaries. Based on simulated catalogues of binary pop
ulations\, we estimate that a fraction of the events will have a detectabl
e imprint of Eddington-level accretion\, when detected by LISA or by LISA
and ground-based detectors (multiband). Accretion can also induce bias in
the binary parameters\, such as the masses and the coalescence time. For t
hese events\, the sky location is well determined and allows for targeted
searches for electromagnetic counterparts\, e.g. with the ATHENA mission o
r SKA.\n\nhttps://indico.sissa.it/event/37/contributions/544/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/544/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tidal Deformability of Black Holes Immersed in Matter
DTSTART;VALUE=DATE-TIME:20200114T094500Z
DTEND;VALUE=DATE-TIME:20200114T100000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-545@indico.sissa.it
DESCRIPTION:Speakers: Vitor Cardoso (CENTRA - Instituto Superior Técnico
and CERN)\, Francisco Duque (GRiT/CENTRA\, Instituto Superior Técnico\, U
niversidade de Lisboa)\n\nThe tidal deformability of compact objects by an
external field has a detectable imprint in the gravitational waves emitte
d by a binary system\, which is encoded in the so-called Tidal Love Number
s (TLNs). For a particular theory of gravity\, the TLNs depend solely on t
he object's internal structure and\, remarkably\, they vanish for black ho
les in general relativity. This fact has gathered attention recently since
a non-zero measurement of the TLNs for a would-be black hole could provid
e evidence of new physics in the strong-field regime. However\, in realist
ic astrophysical scenarios\, a compact object will be surrounded by a non-
vacuum environment. It is\, therefore\, crucial to evaluate if the effect
on tidal deformability due to this environmental matter is comparable to t
he ones characterizing deviations to GR or exotic compact objects (ECOs)\,
such as boson stars\, gravastars\, and wormholes. In this work\, we compu
te the TLNs for model configurations of black holes immersed in matter and
apply our results to astrophysically motivated black hole + accretion dis
k systems. Our results pose some questions regarding the possibility of te
sting strong-field gravity using TLNs.\n\nhttps://indico.sissa.it/event/37
/contributions/545/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/545/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Merger rate of stellar black hole binaries above the pair-instabil
ity mass gap
DTSTART;VALUE=DATE-TIME:20200114T091500Z
DTEND;VALUE=DATE-TIME:20200114T093000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-543@indico.sissa.it
DESCRIPTION:Speakers: Alberto Mangiagli (University of Milan - Bicocca)\,
Alberto Sesana (University of Milan - Bicocca)\, Monica Colpi (University
of Milan - Bicocca)\, Matteo Bonetti (Univeristy of Milan - Bicocca)\n\nIn
current stellar evolutionary models\, the occurrence of pair-instability
supernovae plays a key role in shaping the resulting black hole (BH) mass
population\, preventing the formation of remnants between about $[60\, \\
\, 120] \\rm M_\\odot$.\nWe develop a simple approach to describe BHs beyo
nd the pair-instability gap\, by convolving the initial mass function and
star formation rate with the metallicity evolution across cosmic time and
SEVN\, a code to evolve single stars up to $\\rm M < 350 \\\, \\rm M_\\odo
t$. Under the ansatz that the underlying physics of binary formation does
not change beyond the gap\, we then construct the cosmic population of mer
ging BH binaries.\nWe found that LIGO/Virgo at design sensitivity will det
ect between $\\simeq [0.4\,\\\,7] \\\, \\rm yr^{-1}$ with both mass compon
ents above the gap\, considering the most pessimistic and optimistic scena
rio. Similarly\, the expected rate for third generation ground-based dete
ctors\, like Einstein Telescope\, ranges between $[10\, \\\, 460] \\\, \\
rm yr^{-1}$. \nMoreover\, at lower frequencies\, LISA can individually det
ect these binaries up to thousands of years from coalescence. The number o
f multiband events\, i.e. merging in less than four years\, is expected t
o be in the range $[1\, \\\, 20]$. While ET will detect all these events\
, LIGO/Virgo is expected to detect $< 50\\%$ of them.\nFinally the undetec
ted systems are expected to contribute to the stochastic background in the
LISA band. We estimate that this background may be in principle detected
with a signal-to-noise ratio between $ \\simeq 2.5$ and $\\simeq 80$. \nO
ur work has been accepted for publication: \\href{https://iopscience.iop.o
rg/article/10.3847/2041-8213/ab3f33/meta}{A. Mangiagli et al.\, ApJL 883\,
L27}\n\nhttps://indico.sissa.it/event/37/contributions/543/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/543/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Growth of supermassive black hole seeds in ETG star-forming progen
itors via gaseous dynamical friction: perspectives for GW detections
DTSTART;VALUE=DATE-TIME:20200114T090000Z
DTEND;VALUE=DATE-TIME:20200114T091500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-542@indico.sissa.it
DESCRIPTION:Speakers: Andrea Lapi (SISSA)\, Lumen Boco (SISSA)\, Luigi Dan
ese (SISSA)\n\nIn this talk I will discuss a novel mechanism to grow super
massive black hole seeds in star-forming ETG progenitors at z >1. This env
isages the migration and merging of stellar compact remnants\, via gaseous
dynamical friction\, toward the central regions of such galaxies. I will
show that this process can build up central BH masses of order 10^4 − 10
^6 Msun in a timescale shorter than 10^8 yr\, providing heavy seeds before
standard disk accretion takes over to become the dominant process for fur
ther BH growth. I will discuss the perspectives to detect the merger even
ts between the migrating stellar remnants and the accumulating central sup
ermassive BH via gravitational wave emission with future ground and space-
based detectors such as the Einstein Telescope (ET) and the Laser Interfer
ometer Space Antenna (LISA).\n\nhttps://indico.sissa.it/event/37/contribut
ions/542/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/542/
END:VEVENT
BEGIN:VEVENT
SUMMARY:BMS with applications
DTSTART;VALUE=DATE-TIME:20200114T103000Z
DTEND;VALUE=DATE-TIME:20200114T111500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-546@indico.sissa.it
DESCRIPTION:Speakers: Béatrice Bonga (Radboud University)\n\nThis will be
an overview talk about the Bondi-Metzner-Sachs group\, which is the symme
try group of asymptotically flat spacetimes. After having reviewed its mai
n properties\, I will discuss some applications such as the memory effect.
Next\, I will discuss the BMS algebra in other contexts such as higher di
mensions and black hole horizons. The latter is conjectured to be key in s
olving the information loss paradox. Finally\, I will venture beyond asymp
totic flatness to include superrotations or a positive cosmological consta
nt.\n\nhttps://indico.sissa.it/event/37/contributions/546/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/546/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Constraints on an Effective Field Theory extension to gravity usin
g gravitational-wave observations
DTSTART;VALUE=DATE-TIME:20200114T141500Z
DTEND;VALUE=DATE-TIME:20200114T143000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-547@indico.sissa.it
DESCRIPTION:Speakers: Richard Brito (Sapienza University of Rome)\, Leonar
do Senatore (Stanford University)\, Victor Gorbenko (Institute for Advance
d Study\, Princeton)\, Noah Sennett (Max Planck Institute for Gravitationa
l Physics\, Potsdam)\, Alessandra Buonanno (Max Planck Institute for Gravi
tational Physics\, Potsdam)\n\nGravitational-wave observations of coalesci
ng binary black holes allow for novel tests of the strong-field regime of
gravity. Using the detections of the LIGO and Virgo collaborations\, we pl
ace the first constraints on higher-order curvature corrections that arise
in the effective-field-theory extension of general relativity where highe
r-order powers in the Riemann tensor are included in the gravitational-fie
ld action. We construct gravitational-wave templates that describe the qua
si-circular inspiral stage in this modified theory of gravity\, and use Ba
yesian-selection methods to constrain this theory with respect to General
Relativity. We focus on the two lowest-mass gravitational-wave events obse
rved to date (GW151226 and GW170608)\, but describe a general strategy for
updating constraints with more events.\n\nhttps://indico.sissa.it/event/3
7/contributions/547/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/547/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eikonal QNMs of black holes beyond GR
DTSTART;VALUE=DATE-TIME:20200115T141500Z
DTEND;VALUE=DATE-TIME:20200115T143000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-567@indico.sissa.it
DESCRIPTION:Speakers: Hector Silva\, Kostas Glampedakis\n\nIn this talk we
study the quasi-normal modes of spherically symmetric black holes in modi
fied theories of gravity\, allowing for couplings between the tensorial an
d scalar field degrees of freedom. Using the eikonal approximation and a l
argely theory-agnostic approach\, we obtain analytical results for the fun
damental mode of such black holes.\n\nhttps://indico.sissa.it/event/37/con
tributions/567/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/567/
END:VEVENT
BEGIN:VEVENT
SUMMARY:LISA Data Challenges: Status and future prospects
DTSTART;VALUE=DATE-TIME:20200114T131500Z
DTEND;VALUE=DATE-TIME:20200114T140000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-553@indico.sissa.it
DESCRIPTION:Speakers: Nikos Karnesis\n\nThe LISA Data Challenges (LDC) whe
re established as a common ground with the aim of engaging the community t
o the open LISA data analysis questions. Since the first LDC\, a lot of ex
perience has been gained\, and significant progress has been achieved. In
this talk I will review this progress\, and I will present the purpose and
individual goals of the current LDCs. The status and future prospects wil
l be discussed\, and a small tutorial on the software usage will be given
as well.\n\nhttps://indico.sissa.it/event/37/contributions/553/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/553/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Multi-messenger signals from merging neutron stars
DTSTART;VALUE=DATE-TIME:20200115T081500Z
DTEND;VALUE=DATE-TIME:20200115T090000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-555@indico.sissa.it
DESCRIPTION:Speakers: Francois Foucart\n\nThe first detection of a binary
neutron star star system through gravitational waves and electromagnetic s
ignals (gamma-ray burst\, kilonova\, radio) recently demonstrated the feas
ibility and usefulness of multi-messenger astronomy. In this talk\, I will
provide an overview of the physics of neutron star-neutron star and black
hole-neutron star mergers\, and of what we can learn from gravitational w
aves and electromagnetic signals powered by these events. I will also disc
uss uncertainties in existing models of merging neutron stars\, and how th
ese uncertainties still place important limits on our ability to reliably
extract information from the observation of merging compact objects.\n\nht
tps://indico.sissa.it/event/37/contributions/555/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/555/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The sound of DHOST
DTSTART;VALUE=DATE-TIME:20200114T151500Z
DTEND;VALUE=DATE-TIME:20200114T153000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-552@indico.sissa.it
DESCRIPTION:Speakers: Antoine Lehébel (University of Nottingham)\n\nIn ge
neric higher-order scalar-tensor theories which avoid the Ostrogradsky ins
tability\, the presence of a scalar field significantly modifies the propa
gation of matter perturbations\, even in weakly curved backgrounds. This a
ffects notably the speed of sound in the atmosphere of the Earth. It can a
lso generate instabilities in homogeneous media. I will use this to constr
ain the viable higher-order scalar-tensor models.\n\nhttps://indico.sissa.
it/event/37/contributions/552/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/552/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hearing the strength of gravity (with the Sun)
DTSTART;VALUE=DATE-TIME:20200114T153000Z
DTEND;VALUE=DATE-TIME:20200114T154500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-549@indico.sissa.it
DESCRIPTION:Speakers: Ippocratis Saltas (CEICO - Czech Academy of Sciences
)\n\nGeneric extensions of General Relativity aiming to explain dark energ
y typically introduce fifth forces of gravitational origin. In this talk\,
I will explain how helioseismic observations can provide a powerful and n
ovel tool towards precision constraints of fifth forces\, as predicted by
general theories for dark energy\, and I will discuss the implications for
cosmology.\n\nhttps://indico.sissa.it/event/37/contributions/549/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/549/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The IR limit of Horava Gravity
DTSTART;VALUE=DATE-TIME:20200114T154500Z
DTEND;VALUE=DATE-TIME:20200114T160000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-550@indico.sissa.it
DESCRIPTION:Speakers: Sergey Sibiryakov (EPFL & CERN & INR\, Moscow)\, Mar
io Herrero-Valea (SISSA)\, Lazar Obradovic (EPFL)\n\nHorava Gravity is a r
enormalizable theory of Quantum Gravity which is expected to flow to GR in
the low energy limit. This naive expectation is obstructed by a strongly
coupled interaction when the parameters of the Lagrangian flow to the gene
ral relativistic values. However\, when closely studied\, only self-intera
ctions of the extra scalar mode of the theory are strongly coupled. When m
atter is coupled to HG\, scattering amplitudes naturally flow to the resul
ts given by GR. In other words\, matter remains weakly coupled and interac
ting only through Lorentz invariant operators. I will discuss the implicat
ions of this behavior for HG as a realistic model of gravitational interac
tions.\n\nhttps://indico.sissa.it/event/37/contributions/550/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/550/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Force-free electrodynamics near rotation axis of a Kerr black hole
DTSTART;VALUE=DATE-TIME:20200114T140000Z
DTEND;VALUE=DATE-TIME:20200114T141500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-548@indico.sissa.it
DESCRIPTION:Speakers: Troels Harmark (Niels Bohr Institute)\n\nDespite the
ir potential importance for understanding astrophysical jets\, physically
realistic exact solutions for magnetospheres around Kerr black holes have
not been found\, even in the force-free approximation. Instead approximate
analytical solutions such as the Blandford-Znajek (split-)monopole\, as w
ell as numerical solutions\, have been constructed. In this talk we consid
er a new approach to the analysis and construction of such magnetospheres.
We consider force-free electrodynamics close to the rotation axis of a ma
gnetosphere surrounding a Kerr black hole assuming axisymmetry. This is th
e region where the force-free approximation should work the best\, and whe
re the jets are located. We perform a systematic study of the asymptotic r
egion with (split-)monopole\, paraboloidal and vertical asymptotic behavio
rs. Imposing asymptotics similar to a (split-)monopole\, we find that dema
nding regularity at the rotation axis and the event horizon restricts solu
tions of the stream equation so much that it is not possible for a solutio
n to be continuously connected to the static (split-)monopole around the S
chwarzschild black hole in the limit where the rotation goes to zero. This
provides independent evidence to the issues discovered with the asymptoti
cs of the Blandford-Znajek (split-)monopole in Ref. [1] from which it foll
ows that its perturbative construction is inconsistent.\n\nhttps://indico.
sissa.it/event/37/contributions/548/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/548/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rotating black hole in a higher order scalar tensor theory
DTSTART;VALUE=DATE-TIME:20200114T143000Z
DTEND;VALUE=DATE-TIME:20200114T144500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-551@indico.sissa.it
DESCRIPTION:Speakers: Christos Charmoussis (LPT-Orsay)\n\nWe will discuss
an analytic hairy black hole in a subclass of scalar tensor theories\n\nht
tps://indico.sissa.it/event/37/contributions/551/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/551/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Well-posedness of characteristic formulations of GR
DTSTART;VALUE=DATE-TIME:20200115T094500Z
DTEND;VALUE=DATE-TIME:20200115T100000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-559@indico.sissa.it
DESCRIPTION:Speakers: David Hilditch (Instituto Superior Técnico)\, Thana
sis Giannakopoulos (Instituto Superior Técnico)\, Miguel Zilhão (Institu
to Superior Técnico)\n\nCharacteristic formulations of General Relativity
(GR) have advantages over more standard spacelike foliations in a number
of situations. For instance\, the Bondi-Sachs formalism is at the base of
codes that aim to produce gravitational waveforms of high accuracy\, explo
iting the fact that null hypersurfaces reach future null infinity and henc
e avoid systematic errors of extrapolation techniques. Furthermore\, chara
cteristic formulations in asymptotically anti-de Sitter spacetimes are wid
ely used in the field of numerical holography\, which can provide insights
for the behavior of strongly coupled matter. Well-posedness of the result
ing PDE systems\, however\, remains an open question. The answer to this q
uestion affects the accuracy of the results and the reliability of the con
clusions drawn from numerical studies based on such formulations. A numeri
cal solution can converge to the continuous one only for well-posed PDE sy
stems. The well-posedness of the initial value problem of such systems is
characterized by strong hyperbolicity. We find that the PDE systems arisin
g from the aforementioned formulations are only weakly hyperbolic\, due to
a shared pathological structure in both the asymptotically flat and anti
de-Sitter cases. We present numerical tests that demonstrate this problem
at the practical level.\n\nhttps://indico.sissa.it/event/37/contributions/
559/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/559/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Modelling black hole binaries in the intermediate-mass-ratio regim
e.
DTSTART;VALUE=DATE-TIME:20200115T093000Z
DTEND;VALUE=DATE-TIME:20200115T094500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-560@indico.sissa.it
DESCRIPTION:Speakers: Leor Barack (University of Southampton)\, Mekhi Dhes
i (University of Southampton)\, Adam Pound (University of Southampton)\n\n
We are working to provide accurate modelling of the dynamics and gravitati
onal-wave signatures of black hole inspirals in the intermediate-mass-rati
o regime (IMIRIs) (1:100-1:1000). In doing so we hope to bridge the gap be
tween the accurate modelling of extreme-mass-ratio inspirals achieved thro
ugh black hole perturbation theory\, and that of comparable-mass inspirals
using numerical relativity. Neither approach works well for IMRIs due to
the inability to treat the smaller black hole as a perturbation of the lar
ger and yet disparate length scales remain\, preventing computational effi
ciency in numerical relativity. IMRIs remain an important open problem in
the field as such binary systems are not unlikely sources for Advanced LIG
O and LISA and their observation would provide us with fundamental insight
into black hole formation and astrophysical populations.\n\nOur team at S
outhampton will work with the numerical relativity group at the Albert Ein
stein Institute to tackle the problem through a combination of black-hole
perturbation and numerical relativistic techniques. This talk will give an
overview of a new approach to IMRI modelling: matching an approximate ana
lytic solution near the small black hole to a fully nonlinear numerical so
lution in the bulk of the spacetime. Preliminary results will be presented
from a scalar toy model which tests the implementation of such a matching
procedure.\n\nhttps://indico.sissa.it/event/37/contributions/560/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/560/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Numerical investigation of superradiant instabilities
DTSTART;VALUE=DATE-TIME:20200115T153000Z
DTEND;VALUE=DATE-TIME:20200115T154500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-565@indico.sissa.it
DESCRIPTION:Speakers: Enrico Barausse (Sissa)\, Alexandru Dima (SISSA)\n\n
We present a numerical investigation of the superradiant instability in sp
inning black holes surrounded by a plasma with density increasing when mov
ing closer to the black hole. We try to understand whether superradiant in
stabilities are relevant or not for astrophysical black-holes surrounded b
y matter.\n\nhttps://indico.sissa.it/event/37/contributions/565/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/565/
END:VEVENT
BEGIN:VEVENT
SUMMARY:BMS flux-balance equations as constraints on the gravitational rad
iation
DTSTART;VALUE=DATE-TIME:20200115T090000Z
DTEND;VALUE=DATE-TIME:20200115T091500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-558@indico.sissa.it
DESCRIPTION:Speakers: Ali Seraj (ULB)\, Geoffrey Compere (ULB)\, Roberto O
liveri (Czech Academy of Sciences )\n\nAsymptotically flat spacetimes admi
t infinite dimensional BMS symmetries which complete the Poincare symmetry
algebra with super-translation and super-Lorentz generators. We show that
each of these symmetries lead to a flux-balance equation at null infinity
\, which we compute to all orders in the post-Minkowskian expansion in ter
ms of radiative multipole moments. The ten Poincare flux-balance laws gene
ralize the previously known balance equations to all orders in the post-Mi
nkowskian expansion. The rest of BMS balance laws are novel in the literat
ure and impose infinite number of constraints on the gravitational wavefor
ms. We show that the balance equations for quadrupolar super-translation a
nd super-Lorentz generators give non-trivial constraints at 3PN and 2.5PN
order\, respectively. Our analysis also confirms the surface charge expres
sion for the angular momentum at null infinity derived previously from the
sub-leading soft graviton theorem.\n\nhttps://indico.sissa.it/event/37/co
ntributions/558/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/558/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gauge-invariant approach to the parameterized post-Newtonian forma
lism
DTSTART;VALUE=DATE-TIME:20200115T091500Z
DTEND;VALUE=DATE-TIME:20200115T093000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-557@indico.sissa.it
DESCRIPTION:Speakers: Manuel Hohmann (University of Tartu)\n\nThe paramete
rized post-Newtonian (PPN) formalism is an invaluable tool to assess the v
iability of gravity theories using a number of constant parameters. These
parameters form a bridge between theory and experiment\, as they have been
measured in various solar system experiments and can be calculated for an
y given theory of gravity. The practical calculation\, however\, can becom
e rather cumbersome\, if the field equations involve couplings to addition
al fields. In addition\, the PPN formalism relies on the choice of a parti
cular gauge (or coordinate system)\, which is determined only after solvin
g the field equations. These difficulties can be overcome by applying a ga
uge invariant formalism\, which is conventionally used in cosmological per
turbation theory. The particular nature of the PPN formalism requires pert
urbations of at least quadratic order to be considered\, as well as a diff
erent treatment of space and time directions. In my talk I show how to dev
elop such kind of formalism for gravity theories in metric and tetrad form
ulation and give prospects on how to generalize this treatment to higher p
erturbation orders necessary for calculating high precision orbital motion
.\n\nhttps://indico.sissa.it/event/37/contributions/557/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/557/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Black Hole Perturbation Toolkit
DTSTART;VALUE=DATE-TIME:20200115T131500Z
DTEND;VALUE=DATE-TIME:20200115T140000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-561@indico.sissa.it
DESCRIPTION:Speakers: Niels Warburton\n\nAs we face the task of modelling
small mass-ratio binaries for LISA we\, as a community\, need to spend mor
e time developing waveform models and less time writing and re-writing cod
es. Currently there exist multiple\, scattered black hole perturbation cod
es developed by a wide array of individuals or groups over a number of dec
ades. This project brings together some of the core elements of these code
s into a Toolkit that can be used by anyone. The Black Hole Perturbation T
oolkit\, hosted at https://bhptoolkit.org\, is a collection of open-source
software and data for black hole perturbation theory calculations. In thi
s talk I will overview the motivation for the Toolkit\, give examples of t
he current code and data\, show how you can contribute\, and discuss where
we plan to take the BHPToolkit in the near future.\n\nhttps://indico.siss
a.it/event/37/contributions/561/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/561/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Causal structure of black holes in generalized scalar-tensor theor
ies
DTSTART;VALUE=DATE-TIME:20200115T154500Z
DTEND;VALUE=DATE-TIME:20200115T160000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-564@indico.sissa.it
DESCRIPTION:Speakers: Nicola Franchini (Sissa)\, Thomas P. Sotiriou\, Robe
rt Benkel\, Mehdi Saravani\n\nA modified causal structure of black holes i
n theories beyond general relativity might have implications for the stabi
lity of such solutions. In this talk\, we explore the horizon structure of
black holes as perceived by scalar fields for generalized scalar-tensor t
heories\, which exhibit derivative self-interactions. This means that the
propagation of perturbations on nontrivial field configurations can be sup
erluminal and that the matter fields and gravitational perturbations do no
t necessarily experience the same causal structure.\nUpon linearization\,
and imposing stationarity of the metric and of the scalar field\, we prove
that Killing horizons of the background metric are always Killing horizon
s of the effective metric as well.\n\nhttps://indico.sissa.it/event/37/con
tributions/564/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/564/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Teukolsky formalism for nonlinear Kerr perturbations
DTSTART;VALUE=DATE-TIME:20200115T140000Z
DTEND;VALUE=DATE-TIME:20200115T141500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-563@indico.sissa.it
DESCRIPTION:Speakers: Peter Zimmerman (Albert Einstein Institute Potsdam)\
, Stefan Hollands (University of Leipzig)\, Stephen Green (Albert Einstein
Institute Potsdam)\n\nWe develop a formalism to treat higher order (nonli
near) metric perturbations of the Kerr spacetime in a Teukolsky framework.
We first show that solutions to the linearized Einstein equation with non
vanishing stress tensor can be decomposed into a pure gauge part plus a ze
ro mode (infinitesimal perturbation of the mass and spin) plus a perturbat
ion arising from a certain scalar ("Debye-Hertz") potential\, plus a so-ca
lled "corrector tensor." The scalar potential is a solution to the spin
−2 Teukolsky equation with a source. This source\, as well as the tetrad
components of the corrector tensor\, are obtained by solving certain deco
upled ordinary differential equations involving the stress tensor. As we s
how\, solving these ordinary differential equations reduces simply to inte
grations in the coordinate r in outgoing Kerr-Newman coordinates\, so in t
his sense\, the problem is reduced to the Teukolsky equation with source\,
which can be treated by a separation of variables ansatz. Since higher or
der perturbations are subject to a linearized Einstein equation with a str
ess tensor obtained from the lower order perturbations\, our method also a
pplies iteratively to the higher order metric perturbations\, and could th
us be used to analyze the nonlinear coupling of perturbations in the near-
extremal Kerr spacetime\, where weakly turbulent behavior has been conject
ured to occur. Our method could also be applied to the study of perturbati
ons generated by a pointlike body traveling on a timelike geodesic in Kerr
\, which is relevant to the extreme mass ratio inspiral problem.\n\nhttps:
//indico.sissa.it/event/37/contributions/563/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/563/
END:VEVENT
BEGIN:VEVENT
SUMMARY:On black hole spectroscopy using overtones
DTSTART;VALUE=DATE-TIME:20200115T143000Z
DTEND;VALUE=DATE-TIME:20200115T144500Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-562@indico.sissa.it
DESCRIPTION:Speakers: Valeria Farrari (La Sapeinza )\, Xisco Forteza (Max
Plank\, Hannover)\, Paolo Pani (La Sapienza)\, Swetha Bhagwat (La Sapienza
)\n\nValidating the no-hair theorem with a gravitational wave observation
from a compact binary coalescence presents a compelling argument that the
remnant object is indeed a black hole described by the classical general t
heory of relativity. Validating this theorem relies on performing a spectr
oscopic analysis of the post-merger signal and recovering the frequencies
of either different angular modes or overtones (of the same angular mode).
For an equal mass binary black hole systems\, the angular modes apart fro
m $l=m=2$ are not adequately excited but the overtones provide a prospect
to perform this test. We discuss some challenges associated with performin
g as well as interpreting the results of the tests performed using black h
ole overtones. We investigate the robustness of modelling the post-merger
signal of binary black hole coalescence as a superposition of overtones as
well as study the bias expected in recovered frequencies as a function of
the start time of the analysis. We provide a computationally cheap proced
ure to pick an optimal time to start the spectroscopic analysis of post-me
rger signal. Further\, we find that resolving the frequencies of the overt
ones can be particularly challenging and requires high ringdown SNRs\; for
instance\, the Rayleigh resolvability criterion suggests that for an even
t like GW150914\, an SNR $\\sim 200$ is necessary to resolve the overtone
frequencies.\n\nhttps://indico.sissa.it/event/37/contributions/562/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/562/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cosmic Archaeology with black hole binaries
DTSTART;VALUE=DATE-TIME:20200114T081500Z
DTEND;VALUE=DATE-TIME:20200114T090000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-554@indico.sissa.it
DESCRIPTION:Speakers: Raffaella Schneider\n\nThe existence of massive stel
lar black hole binaries\, with primary black hole (BH) masses greater than
30 -35 Msun was proven by the detection of the gravitational wave (GW) ev
ent GW150914 during the first LIGO/Virgo observing run (O1)\, and successi
vely confirmed by seven additional GW signals discovered by independent an
alyses of the O1 and O2 data. Recently reported O3 alerts suggest that sim
ilar events may have been detected. Building on well established observed
galaxy scaling relations and on our current understanding of stellar evolu
tion at different metallicities\, we find that these systems may be the re
lics of stellar populations forming in low-mass dwarf galaxies before the
end of cosmic reionization. At the other extreme of the mass spectrum of a
strophysical black holes\, the existence of a population of almost 200 bri
ght quasars at z > 6 poses crucial questions about their formation and gr
owth processes. Observationally\, the most distant quasars provide joint c
onstraints on the mass of black-hole ‘seeds’ and their accretion effic
iency. Depending on their birth environmental conditions in the first halo
s collapsing at very high redshifts\, black hole seeds can be light\, heav
y or with intermediate masses. Using ab-initio structure formation models\
, we investigate the relative role of different populations of black hole
seeds in the formation histories of the first super-massive black holes an
d how these formation scenarios may be constrained by future electromagnet
ic and gravitational wave observations. In particular\, future gravitatio
nal wave facilities\, such as LISA and the Einstein Telescope\, will be ab
le to improve our knowledge of these ancient systems\, fully exploiting th
eir potential as cosmic archaeology probes.\n\nhttps://indico.sissa.it/eve
nt/37/contributions/554/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/554/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Testing the no-hair theorem with LIGO and Virgo
DTSTART;VALUE=DATE-TIME:20200116T081500Z
DTEND;VALUE=DATE-TIME:20200116T090000Z
DTSTAMP;VALUE=DATE-TIME:20230610T102300Z
UID:indico-contribution-568@indico.sissa.it
DESCRIPTION:Speakers: Maximiliano Isi\n\nGravitational waves may allow us
to experimentally probe the structure of black holes\, with important impl
ications for fundamental physics. One of the most promising ways to do so
is by studying the spectrum of quasinormal modes emitted by the remnant fr
om a binary black hole merger. This program\, known as black hole spectros
copy\, could allow us to test general relativity and the nature of black h
oles\, including the no-hair theorem---the statement that astrophysical bl
ack holes are fully described by their mass and spin according to the Kerr
metric. I will discuss the prospects for carrying this out with existing
ground-based detectors by relying on the shortest-lived tones of the domin
ant quadrupolar mode (aka 'overtones')\, as well as our recent results fro
m the analysis of GW150914.\n\nhttps://indico.sissa.it/event/37/contributi
ons/568/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/568/
END:VEVENT
END:VCALENDAR