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BEGIN:VEVENT
SUMMARY:Scalarized black holes
DTSTART;VALUE=DATE-TIME:20200115T103000Z
DTEND;VALUE=DATE-TIME:20200115T111500Z
DTSTAMP;VALUE=DATE-TIME:20200807T032205Z
UID:indico-contribution-37-556@indico.sissa.it
DESCRIPTION:Speakers: Daniela Doneva (University of Tuebingen)\nSpontaneou
s scalarization is a very interesting mechanism endowing the compact objec
t with nontrivial scalar field. This mechanism is designed to work only in
the strong gravity regime while remaining the weak field regime practical
ly unaltered. While scalarization was discussed mainly for neutrons stars
in the last few decades\, it was recently discovered that black holes in G
auss-Bonnet gravity can be scalarized as well with the scalar field source
d by the curvature of the spacetime itself that attracted a lot of attenti
on in the field. In the present talk we will review the main achievements
related to scalarized black holes starting with the first papers on the su
bject and paying particular attention to the recent developments in Gauss-
Bonnet gravity and beyond.\n\nhttps://indico.sissa.it/event/37/contributio
ns/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:20200807T032205Z
UID:indico-contribution-37-569@indico.sissa.it
DESCRIPTION:Speakers: Sayak Datta (IUCAA)\nWith the observation of the mul
tiple binary inspirals\, we begin to question whether the components of th
e binary are black holes or some exotic compact objects (ECO). The black h
oleness or the deviation from it can be tested in several ways. The distin
guishing feature of a black hole from other exotic compact objects is the
presence of the horizon. This surface acts as a one-way membrane\, that ab
sorbs energy. Due to this different behavior from ECOs in the late stages
of an inspiral black holes exchange energy\, these backreact on the orbit\
, transferring energy and angular momentum from their spin into the orbit.
This effect is called tidal heating. In Phys.Rev. D99 (2019) no.8\, 08400
1 we argued that the tidal heating can be used as a test for the presence
of the horizon\, and for that\, we introduced horizon parameter (H). Using
H we showed that in LISA\, presence or absence of the horizon can be test
ed accurately as well as precisely. In arXiv:1910.07841 we compute the orb
ital dephasing and the gravitational-wave signal emitted by a point partic
le in circular\, equatorial motion around a spinning supermassive object t
o the leading order in the mass ratio. We showed that the absence of absor
ption by the central object can affect the gravitational-wave signal drama
tically\, especially at high spin. As result it allows us to put an unpara
lleled upper bound on the reflectivity of exotic compact objects\, at the
level of O(0.01)%. This can be used even in near\nequal mass binaries to s
earch for the horizon.\n\nhttps://indico.sissa.it/event/37/contributions/5
69/
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:20200807T032205Z
UID:indico-contribution-37-571@indico.sissa.it
DESCRIPTION:Speakers: Miguel Bezares (SISSA)\nThe direct detection of grav
itational waves (GWs) by the LIGO and VIRGO interferometric detectors has
begun a new era of GW astronomy\, allowing us to study the strong regime o
f gravity through GW signals produced by coalescence of compact objects. I
n this talk\, I will present our numerical studies on coalescence of binar
y Exotic Compact Objects (ECOs) performed by solving the Einstein equation
s with different types of exotic matter: boson stars\, dark boson stars a
nd Neutron Stars that contain a small fraction of dark matter particles c
lustered inside. These binaries lead to different dynamics and gravitation
al waves emission during their coalescence\, which might be crucial to di
stinguish them with 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:20200807T032205Z
UID:indico-contribution-37-570@indico.sissa.it
DESCRIPTION:Speakers: Daniele Pranzetti (Perimeter Institute)\nIn this tal
k I will show how to derive an effective Hamiltonian constraint for the Sc
hwarzschild geometry starting from the full loop quantum gravity Hamiltoni
an constraint and computing its expectation value on coherent states sharp
ly peaked around a spherically symmetric geometry. I then use this effect
ive Hamiltonian to study the interior region of a Schwarzschild black hole
\, where a homogeneous foliation is available. I show how\, for several ge
ometrically and physically well motivated choices of coherent states\, the
classical black hole singularity is replaced by a homogeneous expanding U
niverse. The resultant geometries have no significant deviations from the
classical Schwarzschild geometry in the pre-bounce sub-Planckian curvature
regime\, evidencing the fact that large quantum effects are avoided in th
ese models. In all cases\, we find no evidence of a white hole horizon for
mation. However\, various aspects of the post-bounce effective geometry de
pend on the choice of quantum states and\, in particular\, to the numerica
l value of the Immirzi parameter.\n\nhttps://indico.sissa.it/event/37/cont
ributions/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:20200807T032205Z
UID:indico-contribution-37-572@indico.sissa.it
DESCRIPTION:Speakers: Alexandre Toubiana (APC/IAP)\nBlack holes mimickers
\, e.g. neutron stars or boson stars\, are compact objects with similar pr
operties to black holes.\nThe gravitational wave signal emitted by a binar
y of such putative objects during the inspiral phase is difficult to\ndist
inguish from the one emitted by a black hole binary. Nevertheless\, signif
icant differences might appear in the\npost merger signal. Inspired by th
e known behavior of black holes\, neutron stars and boson stars we \npropo
se a toy model that captures potential characteristics of such systems com
posed by such mimickers. \nThis model can be exploited to assess how well
such signal could be recovered with gravitational waves observations from
\nearth based detectors using standard templates. By analyzing the residua
ls\, i.e. the difference between the injected \nsignal and the best fit te
mplate\, one can also develop strategies to extract the new physics descri
bed by these new signals.\n\nhttps://indico.sissa.it/event/37/contribution
s/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:20200807T032205Z
UID:indico-contribution-37-573@indico.sissa.it
DESCRIPTION:Speakers: Luciano Rezzolla ()\nI will briefly discuss how the
first image of a black hole was obtained\nby the EHT collaboration. In par
ticular\, I will describe the theoretical\naspects that have allowed us to
model the dynamics of the plasma\naccreting onto the black hole and how s
uch dynamics was used to generate\nsynthetic black-hole images. I will als
o illustrate how the comparison\nbetween the theoretical images and the ob
servations has allowed us to\ndeduce the presence of a black hole in M87 a
nd to extract information\nabout its properties. Finally\, I will describe
the lessons we have\nlearned about strong-field gravity and alternatives
to 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:20200807T032205Z
UID:indico-contribution-37-575@indico.sissa.it
DESCRIPTION:Speakers: Marcos Valdes ()\nhttps://indico.sissa.it/event/37/c
ontributions/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:20200807T032205Z
UID:indico-contribution-37-541@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:20200807T032205Z
UID:indico-contribution-37-566@indico.sissa.it
DESCRIPTION:Speakers: Nikolas Andreou (University of Nottingham)\nSpontane
ous scalarization is a mechanism that endows relativistic stars and black
holes with a nontrivial configuration only when their spacetime curvature
exceeds some threshold. The standard way to trigger spontaneous scalarizat
ion is via a tachyonic instability at the linear level\, which is eventual
ly quenched 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 Horndeski action that contribute to the (effective) mass term in th
e linearized equations and\, hence\, can cause or contribute to the tachyo
nic instability that triggers scalarization. We acknowledge networking sup
port by the 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:20200807T032205Z
UID:indico-contribution-37-544@indico.sissa.it
DESCRIPTION:Speakers: Laura Sberna (Perimeter Institute)\nWe study the imp
act of mass accretion in the evolution of LIGO-like black hole binaries. B
ased on simulated catalogues of binary populations\, we estimate that a fr
action of the events will have a detectable imprint of Eddington-level acc
retion\, when detected by LISA or by LISA and ground-based detectors (mult
iband). Accretion can also induce bias in the binary parameters\, such as
the masses and the coalescence time. For these events\, the sky location i
s well determined and allows for targeted searches for electromagnetic cou
nterparts\, e.g. with the ATHENA mission or SKA.\n\nhttps://indico.sissa.i
t/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:20200807T032205Z
UID:indico-contribution-37-545@indico.sissa.it
DESCRIPTION:Speakers: Francisco Duque (GRiT/CENTRA\, Instituto Superior T
écnico\, Universidade de Lisboa)\nThe tidal deformability of compact obje
cts by an external field has a detectable imprint in the gravitational wav
es emitted by a binary system\, which is encoded in the so-called Tidal Lo
ve Numbers (TLNs). For a particular theory of gravity\, the TLNs depend so
lely on the object's internal structure and\, remarkably\, they vanish for
black holes in general relativity. This fact has gathered attention recen
tly since a non-zero measurement of the TLNs for a would-be black hole cou
ld provide evidence of new physics in the strong-field regime. However\, i
n realistic astrophysical scenarios\, a compact object will be surrounded
by a non-vacuum environment. It is\, therefore\, crucial to evaluate if th
e effect on tidal deformability due to this environmental matter is compar
able to the ones characterizing deviations to GR or exotic compact objects
(ECOs)\, such as boson stars\, gravastars\, and wormholes. In this work\,
we compute the TLNs for model configurations of black holes immersed in m
atter and apply our results to astrophysically motivated black hole + accr
etion disk systems. Our results pose some questions regarding the possibil
ity of testing 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:20200807T032205Z
UID:indico-contribution-37-543@indico.sissa.it
DESCRIPTION:Speakers: Alberto Mangiagli (University of Milan - Bicocca)\nI
n 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 bey
ond 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 $\\rm M < 350 \\\, \\rm M_\\od
ot$. Under the ansatz that the underlying physics of binary formation does
not change beyond the gap\, we then construct the cosmic population of me
rging BH binaries.\nWe found that LIGO/Virgo at design sensitivity will de
tect between $\\simeq [0.4\,\\\,7] \\\, \\rm yr^{-1}$ with both mass compo
nents above the gap\, considering the most pessimistic and optimistic scen
ario. Similarly\, the expected rate for third generation ground-based det
ectors\, like Einstein Telescope\, ranges between $[10\, \\\, 460] \\\, \
\rm yr^{-1}$. \nMoreover\, at lower frequencies\, LISA can individually de
tect these binaries up to thousands of years from coalescence. The number
of multiband events\, i.e. merging in less than four years\, is expected
to be in the range $[1\, \\\, 20]$. While ET will detect all these events
\, LIGO/Virgo is expected to detect $< 50\\%$ of them.\nFinally the undete
cted systems are expected to contribute to the stochastic background in th
e LISA band. We estimate that this background may be in principle detected
with a signal-to-noise ratio between $ \\simeq 2.5$ and $\\simeq 80$. \n
Our work has been accepted for publication: \\href{https://iopscience.iop.
org/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:20200807T032205Z
UID:indico-contribution-37-542@indico.sissa.it
DESCRIPTION:Speakers: Lumen Boco (SISSA)\nIn this talk I will discuss a no
vel mechanism to grow supermassive black hole seeds in star-forming ETG pr
ogenitors at z >1. This envisages the migration and merging of stellar com
pact remnants\, via gaseous dynamical friction\, toward the central region
s 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\, p
roviding heavy seeds before standard disk accretion takes over to become t
he dominant process for further BH growth. I will discuss the perspective
s to detect the merger events between the migrating stellar remnants and t
he accumulating central supermassive BH via gravitational wave emission wi
th future ground and space-based detectors such as the Einstein Telescope
(ET) and the Laser Interferometer Space Antenna (LISA).\n\nhttps://indico.
sissa.it/event/37/contributions/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:20200807T032205Z
UID:indico-contribution-37-546@indico.sissa.it
DESCRIPTION:Speakers: Béatrice Bonga (Radboud University)\nThis will be a
n overview talk about the Bondi-Metzner-Sachs group\, which is the symmetr
y group of asymptotically flat spacetimes. After having reviewed its main
properties\, I will discuss some applications such as the memory effect. N
ext\, I will discuss the BMS algebra in other contexts such as higher dime
nsions and black hole horizons. The latter is conjectured to be key in sol
ving the information loss paradox. Finally\, I will venture beyond asympto
tic flatness to include superrotations or a positive cosmological constant
.\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:20200807T032205Z
UID:indico-contribution-37-547@indico.sissa.it
DESCRIPTION:Speakers: Richard Brito (Sapienza University of Rome)\nGravita
tional-wave observations of coalescing binary black holes allow for novel
tests of the strong-field regime of gravity. Using the detections of the L
IGO and Virgo collaborations\, we place the first constraints on higher-or
der curvature corrections that arise in the effective-field-theory extensi
on of general relativity where higher-order powers in the Riemann tensor a
re included in the gravitational-field action. We construct gravitational-
wave templates that describe the quasi-circular inspiral stage in this mod
ified theory of gravity\, and use Bayesian-selection methods to constrain
this theory with respect to General Relativity. We focus on the two lowest
-mass gravitational-wave events observed to date (GW151226 and GW170608)\,
but describe a general strategy for updating constraints with more events
.\n\nhttps://indico.sissa.it/event/37/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:20200807T032205Z
UID:indico-contribution-37-567@indico.sissa.it
DESCRIPTION:Speakers: Kostas Glampedakis ()\nIn this talk we study the qua
si-normal modes of spherically symmetric black holes in modified theories
of gravity\, allowing for couplings between the tensorial and scalar field
degrees of freedom. Using the eikonal approximation and a largely theory-
agnostic approach\, we obtain analytical results for the fundamental mode
of such black holes.\n\nhttps://indico.sissa.it/event/37/contributions/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:20200807T032205Z
UID:indico-contribution-37-553@indico.sissa.it
DESCRIPTION:Speakers: Nikos Karnesis ()\nThe LISA Data Challenges (LDC) wh
ere established as a common ground with the aim of engaging the community
to the open LISA data analysis questions. Since the first LDC\, a lot of e
xperience has been gained\, and significant progress has been achieved. In
this talk I will review this progress\, and I will present the purpose an
d individual goals of the current LDCs. The status and future prospects wi
ll 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:20200807T032205Z
UID:indico-contribution-37-555@indico.sissa.it
DESCRIPTION:Speakers: Francois Foucart ()\nThe first detection of a binary
neutron star star system through gravitational waves and electromagnetic
signals (gamma-ray burst\, kilonova\, radio) recently demonstrated the fea
sibility and usefulness of multi-messenger astronomy. In this talk\, I wil
l provide an overview of the physics of neutron star-neutron star and blac
k hole-neutron star mergers\, and of what we can learn from gravitational
waves and electromagnetic signals powered by these events. I will also dis
cuss uncertainties in existing models of merging neutron stars\, and how t
hese uncertainties still place important limits on our ability to reliably
extract information from the observation of merging compact objects.\n\nh
ttps://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:20200807T032205Z
UID:indico-contribution-37-552@indico.sissa.it
DESCRIPTION:Speakers: Antoine Lehébel (University of Nottingham)\nIn gene
ric higher-order scalar-tensor theories which avoid the Ostrogradsky insta
bility\, the presence of a scalar field significantly modifies the propaga
tion of matter perturbations\, even in weakly curved backgrounds. This aff
ects notably the speed of sound in the atmosphere of the Earth. It can als
o generate instabilities in homogeneous media. I will use this to constrai
n 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:20200807T032205Z
UID:indico-contribution-37-549@indico.sissa.it
DESCRIPTION:Speakers: Ippocratis Saltas (CEICO - Czech Academy of Sciences
)\nGeneric extensions of General Relativity aiming to explain dark energy
typically introduce fifth forces of gravitational origin. In this talk\, I
will explain how helioseismic observations can provide a powerful and nov
el tool towards precision constraints of fifth forces\, as predicted by ge
neral theories for dark energy\, and I will discuss the implications for c
osmology.\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:20200807T032205Z
UID:indico-contribution-37-550@indico.sissa.it
DESCRIPTION:Speakers: Mario Herrero-Valea (SISSA)\nHorava Gravity is a ren
ormalizable theory of Quantum Gravity which is expected to flow to GR in t
he low energy limit. This naive expectation is obstructed by a strongly co
upled interaction when the parameters of the Lagrangian flow to the genera
l relativistic values. However\, when closely studied\, only self-interact
ions of the extra scalar mode of the theory are strongly coupled. When mat
ter is coupled to HG\, scattering amplitudes naturally flow to the results
given by GR. In other words\, matter remains weakly coupled and interacti
ng only through Lorentz invariant operators. I will discuss the implicatio
ns of this behavior for HG as a realistic model of gravitational interacti
ons.\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:20200807T032205Z
UID:indico-contribution-37-548@indico.sissa.it
DESCRIPTION:Speakers: Troels Harmark (Niels Bohr Institute)\nDespite their
potential importance for understanding astrophysical jets\, physically re
alistic exact solutions for magnetospheres around Kerr black holes have no
t been found\, even in the force-free approximation. Instead approximate a
nalytical solutions such as the Blandford-Znajek (split-)monopole\, as wel
l as numerical solutions\, have been constructed. In this talk we consider
a new approach to the analysis and construction of such magnetospheres. W
e consider force-free electrodynamics close to the rotation axis of a magn
etosphere surrounding a Kerr black hole assuming axisymmetry. This is the
region where the force-free approximation should work the best\, and where
the jets are located. We perform a systematic study of the asymptotic reg
ion with (split-)monopole\, paraboloidal and vertical asymptotic behaviors
. Imposing asymptotics similar to a (split-)monopole\, we find that demand
ing regularity at the rotation axis and the event horizon restricts soluti
ons of the stream equation so much that it is not possible for a solution
to be continuously connected to the static (split-)monopole around the Sch
warzschild black hole in the limit where the rotation goes to zero. This p
rovides independent evidence to the issues discovered with the asymptotics
of the Blandford-Znajek (split-)monopole in Ref. [1] from which it follow
s that its perturbative construction is inconsistent.\n\nhttps://indico.si
ssa.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:20200807T032205Z
UID:indico-contribution-37-551@indico.sissa.it
DESCRIPTION:Speakers: Christos Charmoussis (LPT-Orsay)\nWe will discuss an
analytic hairy black hole in a subclass of scalar tensor theories\n\nhttp
s://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:20200807T032205Z
UID:indico-contribution-37-559@indico.sissa.it
DESCRIPTION:Speakers: Thanasis Giannakopoulos (Instituto Superior Técnico
)\nCharacteristic formulations of General Relativity (GR) have advantages
over more standard spacelike foliations in a number of situations. For ins
tance\, the Bondi-Sachs formalism is at the base of codes that aim to prod
uce gravitational waveforms of high accuracy\, exploiting the fact that nu
ll hypersurfaces reach future null infinity and hence avoid systematic err
ors of extrapolation techniques. Furthermore\, characteristic formulations
in asymptotically anti-de Sitter spacetimes are widely used in the field
of numerical holography\, which can provide insights for the behavior of s
trongly coupled matter. Well-posedness of the resulting PDE systems\, howe
ver\, remains an open question. The answer to this question affects the ac
curacy of the results and the reliability of the conclusions drawn from nu
merical studies based on such formulations. A numerical solution can conve
rge to the continuous one only for well-posed PDE systems. The well-posedn
ess of the initial value problem of such systems is characterized by stron
g hyperbolicity. We find that the PDE systems arising from the aforementio
ned formulations are only weakly hyperbolic\, due to a shared pathological
structure in both the asymptotically flat and anti de-Sitter cases. We pr
esent 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:20200807T032205Z
UID:indico-contribution-37-560@indico.sissa.it
DESCRIPTION:Speakers: Mekhi Dhesi (University of Southampton)\nWe are work
ing to provide accurate modelling of the dynamics and gravitational-wave s
ignatures of black hole inspirals in the intermediate-mass-ratio regime (I
MIRIs) (1:100-1:1000). In doing so we hope to bridge the gap between the a
ccurate modelling of extreme-mass-ratio inspirals achieved through black h
ole perturbation theory\, and that of comparable-mass inspirals using nume
rical relativity. Neither approach works well for IMRIs due to the inabili
ty to treat the smaller black hole as a perturbation of the larger and yet
disparate length scales remain\, preventing computational efficiency in n
umerical relativity. IMRIs remain an important open problem in the field a
s such binary systems are not unlikely sources for Advanced LIGO and LISA
and their observation would provide us with fundamental insight into black
hole formation and astrophysical populations.\n\nOur team at Southampton
will work with the numerical relativity group at the Albert Einstein Insti
tute to tackle the problem through a combination of black-hole perturbatio
n and numerical relativistic techniques. This talk will give an overview o
f a new approach to IMRI modelling: matching an approximate analytic solut
ion near the small black hole to a fully nonlinear numerical solution in t
he bulk of the spacetime. Preliminary results will be presented from a sca
lar 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:20200807T032205Z
UID:indico-contribution-37-565@indico.sissa.it
DESCRIPTION:Speakers: Alexandru Dima (SISSA)\nWe present a numerical inves
tigation of the superradiant instability in spinning black holes surrounde
d by a plasma with density increasing when moving closer to the black hole
. We try to understand whether superradiant instabilities are relevant or
not for astrophysical black-holes surrounded by 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:20200807T032205Z
UID:indico-contribution-37-558@indico.sissa.it
DESCRIPTION:Speakers: Ali Seraj (ULB)\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:20200807T032205Z
UID:indico-contribution-37-557@indico.sissa.it
DESCRIPTION:Speakers: Manuel Hohmann (University of Tartu)\nThe parameteri
zed post-Newtonian (PPN) formalism is an invaluable tool to assess the via
bility of gravity theories using a number of constant parameters. These pa
rameters form a bridge between theory and experiment\, as they have been m
easured in various solar system experiments and can be calculated for any
given theory of gravity. The practical calculation\, however\, can become
rather cumbersome\, if the field equations involve couplings to additional
fields. In addition\, the PPN formalism relies on the choice of a particu
lar gauge (or coordinate system)\, which is determined only after solving
the field equations. These difficulties can be overcome by applying a gaug
e invariant formalism\, which is conventionally used in cosmological pertu
rbation theory. The particular nature of the PPN formalism requires pertur
bations of at least quadratic order to be considered\, as well as a differ
ent treatment of space and time directions. In my talk I show how to devel
op such kind of formalism for gravity theories in metric and tetrad formul
ation and give prospects on how to generalize this treatment to higher per
turbation 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:20200807T032205Z
UID:indico-contribution-37-561@indico.sissa.it
DESCRIPTION:Speakers: Niels Warburton ()\nAs we face the task of modelling
small mass-ratio binaries for LISA we\, as a community\, need to spend mo
re time developing waveform models and less time writing and re-writing co
des. Currently there exist multiple\, scattered black hole perturbation co
des developed by a wide array of individuals or groups over a number of de
cades. This project brings together some of the core elements of these cod
es into a Toolkit that can be used by anyone. The Black Hole Perturbation
Toolkit\, hosted at https://bhptoolkit.org\, is a collection of open-sourc
e software and data for black hole perturbation theory calculations. In th
is talk I will overview the motivation for the Toolkit\, give examples of
the current code and data\, show how you can contribute\, and discuss wher
e we plan to take the BHPToolkit in the near future.\n\nhttps://indico.sis
sa.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:20200807T032205Z
UID:indico-contribution-37-564@indico.sissa.it
DESCRIPTION:Speakers: Nicola Franchini (Sissa)\nA modified causal structur
e of black holes in theories beyond general relativity might have implicat
ions for the stability of such solutions. In this talk\, we explore the ho
rizon structure of black holes as perceived by scalar fields for generaliz
ed scalar-tensor theories\, which exhibit derivative self-interactions. Th
is means that the propagation of perturbations on nontrivial field configu
rations can be superluminal and that the matter fields and gravitational p
erturbations do not necessarily experience the same causal structure.\nUpo
n linearization\, and imposing stationarity of the metric and of the scala
r field\, we prove that Killing horizons of the background metric are alwa
ys Killing horizons of the effective metric as well.\n\nhttps://indico.sis
sa.it/event/37/contributions/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:20200807T032205Z
UID:indico-contribution-37-563@indico.sissa.it
DESCRIPTION:Speakers: Stephen Green (Albert Einstein Institute Potsdam)\nW
e develop a formalism to treat higher order (nonlinear) metric perturbatio
ns of the Kerr spacetime in a Teukolsky framework. We first show that solu
tions to the linearized Einstein equation with nonvanishing stress tensor
can be decomposed into a pure gauge part plus a zero mode (infinitesimal p
erturbation of the mass and spin) plus a perturbation arising from a certa
in scalar ("Debye-Hertz") potential\, plus a so-called "corrector tensor."
The scalar potential is a solution to the spin −2 Teukolsky equation wi
th a source. This source\, as well as the tetrad components of the correct
or tensor\, are obtained by solving certain decoupled ordinary differentia
l equations involving the stress tensor. As we show\, solving these ordina
ry differential equations reduces simply to integrations in the coordinate
r in outgoing Kerr-Newman coordinates\, so in this sense\, the problem is
reduced to the Teukolsky equation with source\, which can be treated by a
separation of variables ansatz. Since higher order perturbations are subj
ect to a linearized Einstein equation with a stress tensor obtained from t
he lower order perturbations\, our method also applies iteratively to the
higher order metric perturbations\, and could thus be used to analyze the
nonlinear coupling of perturbations in the near-extremal Kerr spacetime\,
where weakly turbulent behavior has been conjectured to occur. Our method
could also be applied to the study of perturbations generated by a pointli
ke body traveling on a timelike geodesic in Kerr\, which is relevant to th
e 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:20200807T032205Z
UID:indico-contribution-37-562@indico.sissa.it
DESCRIPTION:Speakers: Swetha Bhagwat (La Sapienza)\nValidating the no-hair
theorem with a gravitational wave observation from a compact binary coale
scence presents a compelling argument that the remnant object is indeed a
black hole described by the classical general theory of relativity. Valida
ting this theorem relies on performing a spectroscopic analysis of the pos
t-merger signal and recovering the frequencies of either different angular
modes or overtones (of the same angular mode). For an equal mass binary b
lack hole systems\, the angular modes apart from $l=m=2$ are not adequatel
y excited but the overtones provide a prospect to perform this test. We di
scuss some challenges associated with performing as well as interpreting t
he results of the tests performed using black hole overtones. We investiga
te the robustness of modelling the post-merger signal of binary black hole
coalescence as a superposition of overtones as well as study the bias exp
ected in recovered frequencies as a function of the start time of the anal
ysis. We provide a computationally cheap procedure to pick an optimal time
to start the spectroscopic analysis of post-merger signal. Further\, we f
ind that resolving the frequencies of the overtones can be particularly ch
allenging and requires high ringdown SNRs\; for instance\, the Rayleigh re
solvability criterion suggests that for an event like GW150914\, an SNR $\
\sim 200$ is necessary to resolve the overtone frequencies.\n\nhttps://ind
ico.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:20200807T032205Z
UID:indico-contribution-37-554@indico.sissa.it
DESCRIPTION:Speakers: Raffaella Schneider ()\nThe existence of massive ste
llar black hole binaries\, with primary black hole (BH) masses greater tha
n 30 -35 Msun was proven by the detection of the gravitational wave (GW) e
vent GW150914 during the first LIGO/Virgo observing run (O1)\, and success
ively confirmed by seven additional GW signals discovered by independent a
nalyses of the O1 and O2 data. Recently reported O3 alerts suggest that si
milar events may have been detected. Building on well established observed
galaxy scaling relations and on our current understanding of stellar evol
ution at different metallicities\, we find that these systems may be the r
elics of stellar populations forming in low-mass dwarf galaxies before the
end of cosmic reionization. At the other extreme of the mass spectrum of
astrophysical black holes\, the existence of a population of almost 200 br
ight quasars at z > 6 poses crucial questions about their formation and g
rowth processes. Observationally\, the most distant quasars provide joint
constraints on the mass of black-hole ‘seeds’ and their accretion effi
ciency. Depending on their birth environmental conditions in the first hal
os collapsing at very high redshifts\, black hole seeds can be light\, hea
vy 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 a
nd how these formation scenarios may be constrained by future electromagne
tic and gravitational wave observations. In particular\, future gravitati
onal wave facilities\, such as LISA and the Einstein Telescope\, will be a
ble to improve our knowledge of these ancient systems\, fully exploiting t
heir potential as cosmic archaeology probes.\n\nhttps://indico.sissa.it/ev
ent/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:20200807T032205Z
UID:indico-contribution-37-568@indico.sissa.it
DESCRIPTION:Speakers: Maximiliano Isi ()\nGravitational waves may allow us
to experimentally probe the structure of black holes\, with important imp
lications for fundamental physics. One of the most promising ways to do so
is by studying the spectrum of quasinormal modes emitted by the remnant f
rom a binary black hole merger. This program\, known as black hole spectro
scopy\, could allow us to test general relativity and the nature of black
holes\, including the no-hair theorem---the statement that astrophysical b
lack holes are fully described by their mass and spin according to the Ker
r metric. I will discuss the prospects for carrying this out with existing
ground-based detectors by relying on the shortest-lived tones of the domi
nant quadrupolar mode (aka 'overtones')\, as well as our recent results fr
om the analysis of GW150914.\n\nhttps://indico.sissa.it/event/37/contribut
ions/568/
LOCATION:IFPU\, Miramare campus\, Trieste\, Italy
URL:https://indico.sissa.it/event/37/contributions/568/
END:VEVENT
END:VCALENDAR