This is an overview talk that will outline the progress that has been made in modelling the gravitational-wave signal emitted by coalescing compact binaries. I will briefly introduce the key paradigms and modelling techniques that have led to the successful construction of numerous waveform models before discussing some of the challenges that we face as we transition to the next generation of...
The detection of orbital eccentricity in gravitational waves (GWs) will provide us with unique and valuable information about the astrophysical origin and evolution of compact binary systems. In recent years, the expectations for observing eccentricity signatures in GWs have increased due to the continuous improvement of GW detectors and data-analysis techniques. For this purpose, eccentric...
Compact binaries on eccentric orbits are another class of sources for gravitational wave (GW) detectors that can provide a wealth of information on binaries’ formation pathways and astrophysical environments. However, historically, eccentricity in template waveforms is often ignored in modelled search analyses for compact binaries, which assumes templates for non-precessing quasi-circular...
We develop a modular and user-friendly python code based on the Fisher information matrix formalism to perform population analysis of gravitational- wave events and to make population-level predictions for third-generation detectors. This project is based on the work of [Gair et al (2021) MNRAS 519 2736] who derived a Fisher Matrix formalism to estimate the hyperparameters that characterize a...
The Extreme Mass Ratio Inspirals (EMRIs) are critical astrophysical systems in the study of gravitational waves, where a stellar-mass compact object spirals into a supermassive black hole. Accurate modeling of EMRIs is essential for the success of space-based gravitational wave detectors like LISA. This work presents an improved Effective-One-Body (EOB) model tailored for simulating the EMRIs...
Describing the dynamics of eccentric black hole binaries remains an open problem in General Relativity. Oscualting equations based on energy and angular momentum balance have been found inconsistent with predictions obtained via orbit averaging, particularly in the parabolic regime. This inconsistency arises from the gauge-dependent definitions of energy and angular momentum. We reparametrize...
Gravitational waves (GWs) provide a unique opportunity to test general relativity (GR) in the highly dynamical strong-field regime. So far, the majority of the tests of GR with GW signals have been carried out following parametrized, theory-independent approaches. An alternative avenue consists in the development of inspiral-merger-ringdown (IMR) waveform models in specific beyond-GR theories...
Gravitational wave models have in recent years expanded beyond circularized compact binary systems to cover a larger and larger swath of the parameter space. Models incorporating the spin-precession effect, which occurs when the components' spins are misaligned with the orbital angular momentum, in the quasi-circular case are now routinely used for parameter estimation; meanwhile, several...
Tidal Love numbers provide us a handle to test the nature of compact objects, as well as theories of gravity. There have been several clarifications recently, which makes our understanding of these Love numbers better. But further investigations have led to more confusion. I plan to discuss these recent developments and the confusing nature of recent literature on these issues. I will show...
Despite eight years since the initial detection of gravitational waves from stellar-mass compact-object binaries, the astrophysical origin of these phenomena remains elusive. Recent years have witnessed a growing interest in a novel gravitational wave formation pathway: the active galactic nuclei (AGN) channel. I will describe the key features of the AGN channel, discuss our ongoing efforts in...
The effective one-body (EOB) approach is a proven technique for generating fast and accurate models for the motion and radiation of coalescing compact binaries. At its core, it consists of a specific resummation strategy that takes as input the results of the perturbative schemes used to tackle the two-body problem, notably the post-Newtonian (PN) expansion, the post-Minkowskian (PM)...
Binary-black-hole (BBH) mergers can take place close to a supermassive black hole (SMBH)
while being in a bound orbit around the SMBH. In this paper, we study such bound triple systems
and show that including the strong gravity effects of describing the SMBH with a Kerr metric
can significantly modify the dynamics, as compared to a Newtonian point particle description of the
SMBH. We...
Gravitational radiation reaction for compact binary systems has historically been studied using post-Newtonian theory, which is well adapted for the inspiraling phase and has the advantage of yielding fully analytical results. I will present recent work where we obtain the equations of motion for the two-body problem at 4.5PN order, in a generic frame. We prove for the first time the validity...
According to the no-hair theorem, quasi-normal mode frequencies and damping times are exclusively determined by a black hole's mass and spin. Black hole spectroscopy has shifted from theoretical conjecture to an empirical method for testing these assumptions using current LIGO-Virgo-Kagra observations. We employ a time-domain analysis in an agnostic framework to identify multiple ringdown...
Motivated by the quantum description of gauge theories, we study the phenomenological effects of relaxing the Hamiltonian and momentum constraints in general relativity. We show that the unconstrained theory has new source terms that mimic a pressureless dust that only follows geodesics. The source term may be the simplest explanation for dark matter and generically predicts a charged...
Compact objects are usually described using the perfect fluid formalism. However, in astrophysical processes out of local equilibrium, dissipative effects become important to realistically describe the dynamics of the system.
In this work, we present for the first time the gauge-invariant non-spherical perturbations in a dissipative self-gravitating fluid in spherical symmetry. For this we...
We have studied the stability of wormhole geometries, under massless scalar, electromagnetic, and axial gravitational perturbations, in the context of higher dimensional spacetimes. Intriguingly, the construction of a wormhole spacetime in the presence of higher dimensions, known as braneworld wormholes, does not require the existence of exotic matter fields, unlike the scenario in four...
We present a forecast for the upcoming Einstein Telescope (ET) interferometer with two new methods to infer cosmological parameters. We consider the emission of Gravitational Waves (GWs) from compact binary coalescences, whose electromagnetic counterpart is missing, namely Dark Sirens events. Most of the methods used to infer cosmological information from GW observations rely on the...
In this talk, we present a method to study the properties of ultra-compact, horizonless objects starting from their scattering properties in terms of an inverse problem. The method is based on a combined inversion of Gamow's formula and the Bohr-Sommerfeld rule. Since the direct measurements of transmission and reflection coefficients of astrophysical compact objects are not available from...
Amplitudes of quasi-normal modes in the gravitational-wave signal emitted during the ringdown phase of a binary black-hole merger provide valuable insights into the strong-field non-linear dynamics of the pre-merger phase. While several studies have modeled mode amplitudes for spin-aligned sources, the more complex scenario of precessing sources has received less attention. In this work, we...
The resonant modes of a black hole consist of damped sinusoids, called quasinormal modes. Due to the dissipative nature of the system, the equation governing the modes is non-hermitian. Nevertheless, quasinormal modes have been shown to be orthogonal with respect to a suitable bilinear form defined in Green et al. (2022).
More recently, Cannizzaro et al. (2023) showed that this bilinear form...
In this seminar, we investigate the topic of gravitational waves in the context of Einstein-Cartan theory by exploiting the Blanchet-Damour formalism.
Einstein-Cartan model has been formulated to extend the concepts of general relativity to the microphysical realm in order to establish a connection between gravity and the other fundamental interactions. In this framework, the quantum...
We explore the phenomenological consequences of breaking discrete global symmetries in quantum gravity (QG). We explore how quantum gravity effects, manifested through the breaking of discrete symmetry responsible for the production of primordial black holes (PBH) resulting from Domain Wall annihilations, can have observational effects through gravitational waves. While stable PBHs formed in...
Solutions to Einstein’s field equations (EFEs) are useful in describing compact stellar objects which have very strong gravitational fields and high densities. Finding these solutions is difficult in general because they are a system of complicated nonlinear partial differential equations. Ad hoc methods need to be employed to make them simpler to work with such as assuming a type of symmetry,...
This presentation delves into the study of 'hairy' black holes within the framework of Einstein scalar Maxwell gravity and Einstein scalar Gauss-Bonnet theories, with a focus on revealing new scalarized black hole solutions. We revisit established scalarization phenomena and venture into new solution territories, particularly highlighting the blend of linear and non-linear scalarization in...
We present results on the linear response of four dimensional magnetic black holes and regular topological stars arising from dimensional compactification of Einstein-Maxwell theory in five dimensions.
We discuss the stability of these solutions under both radial and nonradial perturbations, both in the frequency and in the time domain.
Assuming spherical symmetry we consider primordial black hole formation from the collapse of adiabatic cosmological perturbations of a massless scalar field, sourced by a time independent curvature profile $\mathcal{R}(r)$ imposed on super horizon scale. We have proved that a massless scalar field is equivalent to a perfect fluid where the pressure is equal to the total energy density (i.e....
Compact objects are unique probes of the strong gravity regime and may be the key to understanding long-standing puzzles in fundamental physics. These include the nature of dark matter, the possible extension of Einstein's gravity, and the fate of spacetime singularities. The advent of gravitational-wave astronomy provides new observations with present and future interferometers and is a great...
Regarding proposals for modified gravity theories, there is a popular class commonly denominated as scalar-tensor theories, where new scalar fields are introduced that do not interact with gravity in the standard fashion. There is a subclass of such theories that present Screening mechanisms, which allow them to modify gravitational phenomena at large scales while preserving General...
Massive stellar black hole binaries (MBHBs) descendent from population III (Pop. III) binary stars are dark sirens that could play an extremely important role in improving our understanding of the high-redshift Universe. The coalescences of these binaries will be detected by the next generation of ground-based gravitational-wave (GW) detectors; however it is possible that some of the MBHBs...
Black hole quasi-normal mode (QNM) frequency spectrums can probe deviations from General Relativity. We construct an effective field theory scheme for QNMs in shift-symmetric scalar-tensor theories with second order equations, exploiting the behaviour of the black hole’s scalar charge in the large mass limit. We find a drastic simplification; the QNM calculation reduces to solving sourced QNMs...
Phase transitions can play an important role in the cosmological constant problem, allowing the underlying vacuum energy, and therefore the value of the cosmological constant, to change. Deep within the core of neutron stars, the local pressure may be sufficiently high to trigger the QCD phase transition, thus generating a shift in the value of the cosmological constant. The gravitational...
The possibility of a non-zero coupling between local astrophysical objects, such as black holes (BHs), and the large-scale cosmological dynamics, has a quite long history. Recently, there have been interesting developments on the issue, from both theoretical and observational points of view.
In this talk, I will discuss a General Relativity framework allowing the embedding of local objects...
In this presentation, we exploit the Damour-Deruelle solution to derive the analytical expression of the coordinate time in terms of the polar angle. This formula has advantageous applications in both pulsar timing and gravitational-wave theory.
Many works have explored the emergence and properties of compact object solutions including black holes, in models with a metric tensor and a scalar field within the Horndeski framework. Studying the quasinormal mode (QNM) spectrum of hairy black holes is particularly useful when considering the potential of observing hairy solutions in nature. In this talk we discuss how the QNMs of such...
Eccentricity is one of the key parameters to describe a binary system, however, defining it in General Relativity is a highly nontrivial problem. Nevertheless, achieving a consistent definition of orbital eccentricity is a pressing issue for both current and future gravitational wave observations. We present a new approach to consistently define the binary eccentricity in General Relativity...
We propose an adaptive Kernel density estimate (KDE) with selection effects as a non parametric method to study rates and population of massive black hole binary systems, which are expected to observe in LISA Observations. We used simulated LISA data for specific models of massive black hole binaries and applied adaptive KDE to construct distribution in total mass and redshift. We incorporated...
Einstein-Maxwell-Dilaton-Black-Holes (EMDBHs) are a black hole solution of Einstein's equation of General Relativity. EMDBH's have electromagnetic charge (here non-spinning) and a stable scalar field configuration centred on the black hole due to the dilaton coupling in the action between the scalar field and electromagnetism. In this talk we will discuss various phenomenological properties of...
The multi-messenger (MM) observations of binary neutron star (BNS) mergers provide a novel approach to trace the distance-redshift relation, crucial for understanding the expansion history of the Universe and, consequently, testing the presence of Dark Energy (DE). While the gravitational wave (GW) signal offers a direct measure of the distance to the source, the combined efforts of wide-field...
The Einstein-Maxwell-scalar (EMS) theory provides an ideal framework to observe deviations from general relativity. A specific instance of this theory involves a scalar field that is minimally coupled to gravity and non-minimally coupled to the Maxwell field. In addition to the usual Reissner-Nordstrom solutions this theory also admits BH solutions with scalar hair. Another example is the...
Extreme mass ratio inspirals (EMRIs), binary systems composed of a stellar mass compact object (SCO) inspiralling to a supermassive black hole (SMBH), are one of the target sources for the Laser Interferometer Space Antenna (LISA). Since EMRIs may spend about $10^{5}$ cycles in the sensitivity band of the interferometer, they are regarded as golden sources to probe new fundamental fields....
The LISA satellite, recently adopted by ESA, is ready to open a new gravitational wave window, targeting sources dim to ground based detectors like LIGO and Virgo.
Extreme mass-ratio inspirals (EMRIs), composed by a massive black hole and a stellar mass secondary, are a among the most peculiar of such new family of binaries. The inspiral phase of these systems falls within the mHz regime of...
Black-hole ringdowns from binary coalescences encode information about the final state of the remnant through their modes of oscillation, and about their progenitors through the degree of excitation of different modes. We present novel surrogate fits for the excitation amplitudes of black-hole ringdowns from quasi-circular binaries. They are calibrated to numerical relativity simulations and...
Detection and analysis or gravitational wave signals rely on fast and accurate theoretical models.
In particular, the effective-one-body (EOB) framework proved very fruitful in bridging the gap between
analytical (approximated) solutions of Einstein’s equations and numerical relativity (NR) information.
The improved sensitivity of interferometers will allow for detection of different...
Nonlinear effects in black hole perturbation theory may be important for describing a black hole ringdown, as suggested by recent works. I will describe a new class of "quadratic" quasi-normal modes at second order in perturbation theory. Remarkably, not only their frequency but also their amplitude is completely determined by the linear modes themselves. I will present how one can compute...
The detection of a subsolar object in a compact binary merger is regarded as one of the smoking gun signatures of a population of primordial black holes (PBHs). We critically assess whether these systems could be distinguished from stellar binaries, for example composed of white dwarfs or neutron stars, which could also populate the subsolar mass range. At variance with PBHs, the...
Recently, studies on numerical evolutions of eccentric binary inspirals found a several orders of magnitude enhancement of the post-ringdown tail amplitude. This characteristic might render the tail a phenomenon of observational interest, opening the way to experimental verification of this general relativistic prediction in the near future. I will present an analytical perturbative model that...
The first detection of a neutron star binary merger has made sharp reality the long-standing paradigm that these cosmic fireworks are exciting laboratories for extreme physics. To get the most out of observations, however, we need accurate modelling of the merger dynamics via numerical relativity simulations. In this respect, the large amount of numerical work carried out over the last decade...
Third-generation (3G) gravitational-wave (GW) detectors like the Einstein Telescope (ET) will observe binary black hole (BBH) mergers at redshifts up to z ∼ 100. However, unequivocal determination of the origin of high-redshift sources will remain uncertain, due to the low signal-to-noise ratio (SNR) and poor estimate of their luminosity distance. This study proposes a machine learning...
Astrophysical observations of neutron stars allow us to study the physics of matter at extreme conditions which are beyond the scope of any terrestrial experiments. In this work, we perform a Bayesian analysis putting together the available knowledge from the nuclear physics experiments, observations of different X-ray sources, and gravitational wave events to constrain the equation of state...
The multimessenger event GRB 170817A confirmed that short gamma-ray burst jets can be launched from the remnants of a binary neutron star merger environment. The electromagnetic properties of such jets are expected to strongly affect their structure and propagation. In particular, the impact of a finite conductivity may play a key role in the early stages of propagation, i.e. when the jet...
The gravitational collapse of a massive star with a fast-rotating core sets the stage for the onset of magnetorotational core-collapse supernovae (CCSN). The accreting central compact object (either a black hole or a proto-magnetar) is believed to be the central engine that can power up outstanding stellar explosions such as hypernovae and long gamma-ray bursts (GRBs). Current...
The rate of GW detections will soar from hundreds to millions per year
as detectors improve, revealing the population properties of BH mergers
in great detail. Such properties encode valuable information about how
stars form and evolve in galaxies very different from our own. They can
provide complementary constraints on the cosmic chemical history and on
star formation in environments...
The inference of source parameters from gravitational-wave signals relies on theoretical models that describe the emitted waveform. Different model assumptions on which the computation of these models is based could lead to biases in the analysis of gravitational-wave data. In this work, we sample directly on four state-of-the-art binary black hole waveform models from different families, in...
In dense star clusters stars may be disrupted in close encounters with stellar mass black holes. These transients are addressed as “micro-Tidal Disruption Events” (TDEs). To date, micro-TDEs have not yet been observed but they are promising multi-messenger sources predicted to be detected by next gravitational waves (GW) observatories (i.e. DECIGO) and future all-sky surveys (i.e. LSST,...
I introduce $floZ$, an improved method based on normalizing flows, for estimating the Bayesian evidence (and its numerical uncertainty) from a set of samples drawn from the unnormalized posterior distribution. I validate it on distributions whose evidence is known analytically, up to 15 parameter space dimensions and I demonstrate its accuracy for up to 200 dimensions with $10^5$ posterior...
The tidal Love numbers of self-gravitating compact objects describe their response to external tidal perturbations, such as those from a companion in a binary system, offering valuable insights into their internal structure. For static tidal fields, asymptotically flat black holes in vacuum exhibit vanishing Love numbers in general relativity, even though this property is sensitive to the...
The properties of binaries hosting a Wolf-Rayet star and a compact object
(black hole or neutron star) suggest that such systems could be the progen-
itors of binary compact objects merging via gravitational wave emission. It
is difficult to distinctively determine the road leading to these mergers: many
stellar and binary physical models are still poorly constrained and...
Efficient gravitational waveform models enable us to analyze gravitational wave signals and extract information about the source properties of the compact binary involved in the merger. In this talk, we discuss the improvements made to the NRTidal model, a state-of-the-art model used to describe the tidal interactions between the components of binary neutron stars. The updates include a new...
The study of neutron stars, dense remnants of stellar core collapse, provides a unique opportunity to explore the fundamental properties of matter under extreme conditions. In this talk I will review the status of our current understanding of the neutron star equation of state (EOS) through measurements derived from multi-messenger observations of binary neutron star mergers. Then, focusing on...
Dense astrophysical environments, such as globular clusters, could host populations of black holes undergoing scatterings and dynamical captures. The gravitational wave event GW190521 may have originated from such a system, underscoring the need for accurate descriptions to fully leverage the scientific potential of current and future gravitational wave detectors.
We briefly introduce the...
In this talk I will highlight recent developments in computing classical gravity observables within the post-Minkowskian scheme using QFT techniques, the double copy and modern tools of scattering amplitudes.
Gravitational waves (GW) from chirping binary black holes (BBHs) provide unique opportunities to test general relativity (GR) in the strong-field regime. However, testing GR can be challenging when incomplete physical modeling of the expected signal gives rise to systematic biases. In this talk, we discuss the potential influence of wave effects in gravitational lensing (also known as...
We have attempted to mitigate the challenge of connecting the neutron star (NS) properties with the nuclear matter parameters that describe equations of state (EOSs). The efforts to correlate various neutron star properties with individual nuclear matter parameters have been inconclusive.
A Principal Component Analysis is employed as a tool to uncover the connection between multiple nuclear...
