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6/5/23, 8:50 AM
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6/5/23, 9:00 AM
The arrival of third-generation gravitational wave detectors in 2030-2035, such as the Einstein Telescope and the space-based LISA detector, promises major advances in our understanding of the theory of gravity and of compact objects. However, the very high precision of the expected data presents us with new challenges, including distinguishing, when analyzing gravitational wave data, between...
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6/5/23, 9:40 AM
New light scalar degrees of freedom may alleviate the dark matter and dark energy problems, but if coupled to matter, they generally mediate a fifth force. In order for this fifth force to be consistent with existing constraints, it must be suppressed close to matter sources, e.g. through a non-linear screening mechanism. The focus of this talk will be shift-symmetric scalar-tensor theories...
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6/5/23, 10:50 AM
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6/5/23, 2:00 PM
Working within the space of solutions of GR and tuning to the threshold of black hole formation, we arrive at extreme spacetimes which are generally expected to contain naked singularities. In the spherical setting such configurations have been accurately studied by numerical work for three decades. This resulted in a beautiful understanding of the threshold of collapse through a mathematical...
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6/5/23, 2:40 PM
A model system of equations that serves as a model for the Einstein field equation in generalised harmonic gauge called the good-bad-ugly system is studied in the region close to null and spatial infinity in Minkowski spacetime. This analysis is performed using H. Friedrich’s cylinder construction at spatial infinity and defining suitable conformally rescaled fields. The results are translated...
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6/5/23, 3:50 PM
Einstein-dilaton-Gauss-Bonnet (EdGB) is a theory of modified gravity in which a dilaton-type scalar field is nonminimally coupled to quadratic curvature terms via an exponential function. Black holes (BHs) in this theory are particularly interesting since they possess a critical configuration with minimum mass and finite Hawking temperature. This means that a critical BH loses mass due to...
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6/5/23, 4:30 PM
In this talk, I will present a study of the qualitative features of stationary solutions with kinetic screening for different couplings to matter. As for the dynamics, I will illustrate with an explicit example how different ``completions'' of k-essence can allow for stable time evolutions with numerical relativity. The latter, despite the original theory appearing to be ill (which is a...
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6/5/23, 5:10 PM
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6/5/23, 6:00 PM
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6/6/23, 9:00 AM
Third-generation gravitational-wave detectors and the space-based LISA mission will observe binaries in galactic centers involving supermassive black holes with millions of solar masses. These binaries can interact gravitationally with accretion disks, dark matter halos and other compact objects. The role these astrophysical structures play in the evolution and gravitational-wave signature of...
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6/6/23, 9:40 AM
Black-hole spectroscopy is one of the most promising tools to test gravity in extreme regimes and to probe the nature of black holes. However, tests based on ringdown observations are currently limited by the lack of parametrization that are both robust and accurate, able to capture generic modifications of the Kerr spectrum. In this talk I will present a new observable-based parametrization...
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6/6/23, 10:50 AM
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6/6/23, 2:00 PM
Testing the strong gravity regime of general relativity is a primary goal of gravitational wave detectors. While it is expected that corrections to GR are small and unlikely to be identified with individual events, third generation GW detectors will allow detection of tens-of-thousands of events per year. Therefore, they will pave the way to precision tests by carefully stacking all the...
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6/6/23, 2:40 PM
The motion of S2, one of the stars closest to the Galactic Center, has been measured accurately and used to study the compact object at the centre of the Milky Way. It is commonly accepted that this object is a supermassive black hole but the nature of its environment is open to discussion. In this talk I’m going to show how the motion of S2 can be used to investigate the possibility that dark...
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6/6/23, 3:50 PM
I will present the analysis of the ringdown phase of the first
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detected black-hole merger, GW150914, using a simulation-based
inference pipeline based on masked autoregressive flows. We obtain
approximate marginal posterior distributions for the ringdown
parameters, namely the mass, spin, and the amplitude and phases of the
dominant mode and its first overtone. Thanks to the locally... -
6/6/23, 4:30 PM
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6/7/23, 9:15 AM
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6/7/23, 9:30 AM
This short talk will present a brief overview of the problem that motivates this workshop, and our goals for what we hope to get out of our time together.
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6/7/23, 9:50 AM
This talk will review how one models the evolution of extreme mass ratio binary systems and the gravitational waveforms which they produce. It is linked to the talk which follows by Leor Barack.
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6/7/23, 10:15 AM
I will review recent work (by others) on post-adiabatic models for EMRIs and IMRIs, illustrating the remarkable effectiveness of the small-mass-ratio expansion even at mass ratios that are not so small. Interesting synergies with NR and EOB calculations will be discussed. Whether one thinks of environmental effects as signals to be extracted or as noise to be removed, it is crucial to have at...
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6/7/23, 11:15 AM
Gravitational-wave observations of extreme mass ratio inspirals (EMRIs) hold incredible potential to probe gravity, astrophysical and exotic environments. On the astrophysical side, the gas disks of active galactic nuclei can induce detectable “migration” torques on the binary. Within a Bayesian framework, we find that LISA could detect migration for a wide range of disk viscosities and...
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6/7/23, 2:00 PM
The "vanilla" extreme mass ratio inspiral (EMRI) is a compact object spiraling onto a perfectly isolated massive black hole in general relativity. I will discuss how this can change due to an astrophysical environment and what needs to be done to faithfully and frugally capture these effects in waveforms. In the second half, I will turn attention to the fact that EMRIs may also act on the...
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6/7/23, 2:45 PM
Ultralight dark matter is an exciting alternative to the standard cold dark matter paradigm, reproducing its large scale predictions, while solving most of its potential tension with small scale observations (like the "cusp-core" and "missing satellites" problems). If dark matter is made of some new ultralight bosonic particle, relatively dense and large structures are expected to form at the...
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6/7/23, 4:00 PM
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6/8/23, 9:30 AM
LISA has the potential to place stringent constraints on the astrophysical environments of the black holes generating the gravitational waves it observes. However, this will only be possible with careful analysis of the LISA data stream, which poses significant challenges. I will give an overview of the current state of knowledge of LISA data analysis and then discuss outstanding challenges...
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6/8/23, 10:45 AM
Recent observations from the LIGO/Virgo/KAGRA collaboration have suggested that stellar-mass black hole binaries (SBHBs) could form in active galactic nuclei (AGN). If so, we expect the environment in which these binaries are embedded to leave an imprint on the gravitational wave signal they emit. These deviations from vacuum waveforms should be more important in the early inspiral, i.e. at...
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6/8/23, 11:30 AM
Due to superradiant instabilities, clouds of ultralight bosons can spontaneously grow around rotating black holes, creating so-called "gravitational atoms". In this talk, we discuss their dynamical effects on binary systems. We first focus on open orbits, showing that the presence of a cloud can increase the cross section for the dynamical capture of a compact object by more than an order of...
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6/8/23, 2:15 PM
Gravitational wave sources typically evolve in gaseous environments and it is crucial to understand what are the possible emission signatures that derive from this interaction.
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We produce synthetic X-ray light curves compatible with X-ray data from the four confirmed Quasi Periodic Eruption (QPEs) sources (GSN 069, eRO-QPE1, eRO-QPE2 and RX J1301.9+2747), using a semi-analytical model based... -
6/8/23, 3:00 PM
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6/9/23, 9:30 AM
The effective-one-body (EOB) approach is based on a mapping between the two-body problem in GR and the motion of a single body in an effective metric. This approach already efficiently provides templates for the comparable-mass compact binary coalescences observed by the LVK collaboration, but is also flexible enough to reach a wider coverage of the parameter space. If for comparable-mass...
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6/9/23, 10:45 AM
I will discuss the evolution of SMBHBs from kpc down to final coalescence including the dynamical friction, stellar and gaseous hardening and gravitational wave phases. In particular I will focus on how the properties of very massive systems observable with pulsar timing arrays.
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6/9/23, 11:30 AM
Extreme-mass-ratio inspirals (EMRIs) will allow precise measurements of trajectories of a compact object in the strong-gravity regime around a supermassive black hole, making the detection of beyond-GR effects possible. However, environmental effects such as an accretion disk, can give rise to dephasing effects in the compact object's trajectories, with the potential to raise false alarm in...
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6/9/23, 2:00 PM
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6/9/23, 3:00 PM
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