The open question of whether a black hole can become tidally deformed by an external gravitational field has profound implications for fundamental physics, astrophysics and gravitational-wave astronomy. Love tensors characterize the tidal deformability of compact objects such as astrophysical (Kerr) black holes under an external static tidal field. We prove that all Love tensors vanish...

The three body-problem, even in the simple Newtonian case, exhibits very rich dynamical behaviors. The study of a hierachical configuration, in which a close inner binary is orbited by a distant perturber, has been initiated by Lidov and Kozai in the 60's. The eccentricity oscillations that they discovered is particularly relevant to gravitational wave astronomy. On the other hand, several...

We derive the static Schwarzschild-Tangherlini metric by extracting the classical contributions from the multiloop vertex functions of a graviton emitted from a massive scalar field. At each loop order the classical contribution is proportional to a unique master integral given by the massless sunset integral. By computing the scattering amplitudes up to three-loop order in general dimension,...

We study the gravitational radiation emitted during the scattering of two spinless bodies in the post-Minkowskian Effective Field Theory approach. We derive the conserved stress-energy tensor linearly coupled to gravity and the classical probability amplitude of graviton emission at leading and next-to-leading order in the Newton’s constant $G$. The amplitude can be expressed in compact

form...

We present GPE, a GPU-accelerated parameter estimation package for gravitational waves from compact binary coalescence sources. This stand-alone program is adapted from the nested sampling flavor of LALInference. Two main parallelization methods are implemented: (1) the frequency-domain waveform and likelihood calculations, (2) and the prior sampling portion in the nested sampling algorithm....

A major activity of the LIGO-Virgo-KAGRA collaboration is to build algorithms able to infer from the detected gravitational wave signals the posterior distributions of the parameters defining their sources: angles in the sky, distance from us, masses etc. Current algorithms like MCMC and Nested Sampling have already demonstrated with success their ability to do so during the first three runs...

Current gravitational-wave data analysis of merging binary black holes accounts for two precessing spins, allowing inference of the six spin degrees of freedom. Nonetheless, it is convenient to use effective parameters to interpret detections; the effective aligned spin $\chi_{\rm{eff}}$ and the effective precessing spin $\chi_{\rm{p}}$ measure components parallel and perpendicular to the...

With LISA mission, the detection of galactic binaries as sources of gravitational waves promises an unprecedented wealth of information about these systems, but also raises several challenges in signal processing. In particular, the variety of sources and the presence of both planned and unplanned gaps call for the development of robust methods. We describe here an original non-parametric...

LISA is a future space-based gravitational wave detector that will a new window into the gravitational universe in the mHz range. Among LISA targets, coalescences of massive black hole binaries (MBHB) will be detected with unprecedented signal-to-noise ratios, and might enable multimessenger observations with instruments such as Athena, LSST and SKA. Modelling LISA's ability to locate these...

Continuous gravitational waves (CWs) from asymmetric spinning neutron stars are among the most interesting, although still undetected, targets of the Advanced LIGO-Virgo detectors. The search for this class of signals is difficult due to their expected weakness, and can be very computationally expensive when the source parameters are not known.

The stochastic group uses fast and consolidated...

We show that the odds of the mass-gap (secondary) object in GW190814 being a neutron star (NS) improve if one allows for a stiff high-density equation of state (EoS) or a large spin. Since its mass is $\in (2.50,2.67) M_{\odot}$, establishing its true nature will make it either the heaviest NS or the lightest black hole (BH), and can have far-reaching implications on NS EoS and compact object...

We make extensive numerical studies of masses and radii of proto-neutron stars during the first second after their birth in core-collapse supernova events. We use a quasi-static approach for the computation of proto-neutron star structure, built on parameterized entropy and electron fraction profiles, that are then evolved with neutrino cooling processes. We vary the equation of state of...

Gravitational waves provide a unique opportunity to better constrain the dynamics in the interior of proto-neutron stars during core collapse supernovae. Convective motions inside the proto-neutron star play an important role in determining neutron star magnetic fields. In paticular, numerical models suggest that a convective dynamo could explain magnetar formation in presence of fast...

Measurements of neutron star macrophysical properties thanks to multi-messenger observations offer the possibility to constrain the properties of nuclear matter. Indeed cold and dense matter as found inside neutron stars, in particular in their core, is not accessible to terrestrial laboratories.

We investigate the consequences of using equations of state that employ models for the core and...

I will highlight the immense discovery potential on early universe physics stemming from gravitational wave probes. To this aim, I will survey two approaches to inflation, from the particular (axion inflation models) to the general (an EFT approach).

I will show how a characterisation of the GW signal that includes (i) frequency profile, (ii) chirality, (iii) higher-point functions, (iv)...

A scalar field with large kinetic energy can dominate the Universe at early times and generates the so-called kination era. We present a natural and well-motivated particle physics realization, based simply on a Peccei-Quinn mechanism. The presence of kination imprints a smoking-gun spectral enhancement in the stochastic gravitational-wave (GW) background. Current and future-planned GW...

The generation of primordial magnetic fields and its interaction with the primordial plasma during cosmological phase transitions is turbulent in nature. I will describe and discuss results of direct numerical simulations of magnetohydrodynamic (MHD) turbulence in the early universe and the resulting stochastic gravitational wave background (SGWB). In addition to the SGWB, the primordial...

A first-order phase transition in the early universe would have given rise to a stochastic gravitational wave background which may be observable today. Starting from a particle physics Lagrangian, the first step in making predictions of the gravitational wave signal is to understand the thermodynamics of the phase transition. In this talk, I will discuss the current situation regarding the...

Several observations using electromagnetic signal have led to a paradigm shift in our understanding of the Universe, with the realization that two unknown quantities - namely dark matter and dark energy - constitute about 95% of the Universe, even though their existence could not be explained by the known laws of physics and fundamental particles discovered until now. Moreover, measurements of...

I will present the methodology for constraining the Hubble parameter and modified GW propagation with “dark sirens” (namely, compact binary coalescences without an electromagnetic counterpart) and galaxy catalogs.

I will introduce in particular some relevant improvements to the treatment of the latter, such as their completeness, and discuss the correct treatment of selection bias. I will...

The detection of gravitational waves (GWs) and an accompanying electromagnetic (E/M) counterpart have been suggested as a future probe for cosmology and theories of gravity. In this work, we present calculations of the luminosity distance of sources taking into account inhomogeneities in the matter distribution that are predicted in numerical simulations of structure formation. In addition, we...

Neutron stars (NSs), being one of the most enigmatic stellar remnants with incredibly dense core and sturdy crust, can be considered as the best laboratory in the universe to appraise many astrophysical models of the strong gravitational field regime. We analyse the effects of dark matter on the properties and curvature of the NS with the help of relativistic mean-field (RMF) formalism using...

The recent discovery of gravitational waves has opened new horizons. The LIGO-Virgo events have made possible to estimate rates, masses, eccentricities, and projected spins of merging black holes (BHs) for the fist time. The astrophysical origin of these mergers is among the most puzzling open questions of our time. Two primary channels have been proposed to explain the observed population of...

With the recent publication of the second gravitational wave transient catalog by the LIGO-Virgo collaboration (LVC), the number of binary compact object mergers has risen dramatically, from a dozen to ~ 50 events. From these detections, the LVC inferred the merger rate density both in the local Universe and as a function of redshift. It is then of foremost importance to compare the merger...

Different scenarios for the formation and evolution of massive black holes lead to different predictions for the population of massive black holes in the Universe. By reverse engineering the problem, we can use LISA observations to discriminate between different scenarios. However, the Universe is unlikely to be described by a single model. This can be accounted for by introducing mixing...

In 2034, within the rapidly changing landscape of gravitational-wave astronomy, the Laser interferometer Space Antenna will be the first space-based detector that will observe the gravitational spectra in the millihertz frequency band. It has recently been proposed that numerous LIGO/VIRGO sources will also be detectable by LISA. LISA will be able to detect binary black holes from our Milky...

Current and future surveys are going to shed light on the formation and evolution of massive black hole binaries. While current pulsar-timing experiments will detect a gravitational wave (GW) background signal generated by the incoherent superposition of GWs from the whole population of massive binary black holes, the forthcoming LISA experiment will likely detect singular coalescences events....

Nowdays we are able to resolve more and more compact binary merger events as our detector sensitivities improve. However the detected sources are loud and close events, suggesting a large number of non-resolved binary mergers participating to a CBC background. I will present this background computed from a population I/II stars ehanced with a young cluster population simulated from dynamical...

Multi-messenger studies have been vitalized by GW170817 in which diverse messengers - photons and gravitational waves - provide a new picture of the collision of two neutron stars. In this talk, I will first review briefly how coherent analysis of the messengers can not only better constrain the astrophysical scenarios at play, but also further knowledge on the cosmology and nuclear physics...

Tidal disruption events (TDEs) take place when a star orbiting around a black hole (BH) is fully or partially disrupted by the black hole tides. This occurrence can be used as a way to reveal the presence of quiescent BHs through the Universe. With this talk, I will first describe general features of TDEs. Then, I will explore the possibility of detecting them via gravitational waves (GWs)...

Massive black hole binaries (MBHBs) of $10^5 \, \rm M_\odot - 3 \times 10^7 \, \rm M_\odot $ merging in low redshift galaxies ($z\le4$) are sufficiently loud to be detected weeks before coalescence with LISA. This allows us to perform the parameter estimation *on the fly*, i.e. as a function of the time to coalescence during the inspiral phase, relevant for early warning of the planned LISA...

Gravitational theories differing from General Relativity may explain the accelerated expansion of the Universe without a cosmological constant. However, their viability crucially depends on a “screening mechanism” needed to suppress, on small scales, the fifth force driving the cosmological acceleration. I will discuss a scalar-tensor theory with first-order derivative self-interactions...

I will present extreme mass ratio inspirals (EMRIs), during which a small body spirals into a supermassive black hole, in gravity theories with additional scalar fields. No-hair theorems and properties of known theories that manage to circumvent them introduce a drastic simplification to the problem: the effects of the scalar on supermassive black holes, if any, are mostly negligible for EMRIs...

In this talk I present three recent works [1,2,3] that aim to enhance our understanding of reconstructing black hole space-times from different type of observations. While gravitational wave detectors like LIGO/Virgo allow to perform black hole spectroscopy of stellar mass black holes, images such as those produced by the Event Horizon Telescope provide information of the shadow from super...

Gravitational waves from the coalescence of compact binaries provide a unique opportunity to test gravity in strong field regime. In particular, the postmerger phase of the gravitational signal is a proxy for the nature of the remnant.

This is of particular interest in view of some quantum-gravity models which predict the existence of horizonless compact objects that overcome the paradoxes...

In gravity theories that exhibit spontaneous scalarization, astrophysical objects are identical to their general relativistic counterpart until they reach a certain threshold in compactness or curvature. Beyond this threshold, they acquire a non-trivial scalar configuration, which also affects their structure. The onset of scalarization is controlled only by terms that contribute to linear...

Effective field theories (EFTs) facilitate what might otherwise be completely untenable calculations by helping us focus on only the most relevant physics at hand. Applied to general relativity, these techniques have famously improved our handle on post-Newtonian theory over the last decade, and extensions of these ideas are now also being developed to study how binary systems evolve when they...

A.E. Volvach, L.N. Volvach, M. G. Larionov

Estimates of the level of gravitational wave (GW) coming from 3C 454.3 show that 3C 454.3 is currently the most powerful GW emitter. Based on the obtained data, we consider the characteristics of the gravitational radiation of this system, as well as the lifetime before merging, and possible variations in companion orbits.

Due to the constant...

Mixed space-time spectral analysis was applied for the detection of seismic waves passing through the west-end building of the Virgo interferometer. The method enables detection of every single passing wave, including its frequency, length, direction, and amplitude. A thorough analysis aimed to improving sensitivity of the Virgo detector was made for the data gathered by 38 seismic sensors, in...