arXiv subjects

Matteo Della Rocca

Publications and source records attributed to Matteo Della Rocca.

8 recordsLinked to original sources

arXiv2026

Ruling out matter-induced bumps in black-hole effective potentials

Matter fields localized around black holes can produce small secondary bumps in the effective potentials governing black-hole perturbations, potentially leading to quasinormal-mode spectral instabilities and late-time echoes. Considering physically motivated models of anisotropic fluids surrounding a spherically symmetric black hole, we show that the appearance of such a secondary bump is accompanied by either singular matter profiles or divergent characteristic speeds in the fluid. These features indicate that the corresponding matter configurations are unphysical. We further demonstrate that a secondary bump in the effective potential does not necessarily imply the existence of additional light rings in the spacetime.

gr-qc↗

arXiv2026

Vanishing of all redshift modes in Schwarzschild ringdown

Several studies of black hole ringdown from particles plunging into black holes have identified contributions decaying at integer multiples of the surface gravity, called redshift modes, horizon modes, and direct waves. We show that, for Schwarzschild black holes, every one of these contributions has vanishing amplitude in the observable waveform. The cancellation follows from causality, which forces the source-integrated Green function to vanish on the light cone. Individual quasi-normal mode overtones still carry non-zero redshift-mode contributions, but these cancel exactly once the sum over overtones is performed; the so-called impulsive contribution to the waveform acts precisely as the counterterm enforcing this cancellation. Finally, we provide a motivation to the standard regularization of quasinormal mode excitation coefficients since divergences give rise to vanishing redshift modes.

gr-qc↗

arXiv2026

Adiabatic evolution of asymmetric binaries on generic orbits with new fundamental fields I: characterization of gravitational wave fluxes

We investigate the dynamics of asymmetric binaries in extensions of General Relativity featuring a massless scalar field non-minimally coupled to gravity, focusing on the interplay between eccentricity and inclination in fully generic bound orbits. Building on an effective field theory framework tailored to extreme- and intermediate-mass-ratio inspirals, we compute scalar-field perturbations using a new arbitrary-precision C++ code capable of evolving perturbations along generic Kerr geodesics, STORM. We investigate the complete set of scalar fluxes at infinity and through the horizon across the relevant parameter space and analyze their harmonic structure as a function of orbital geometry and black-hole spin. Our results advance ongoing efforts to construct accurate waveform models for asymmetric binaries beyond GR and lay the groundwork for precision tests of fundamental physics with next-generation gravitational-wave detectors.

gr-qc↗

arXiv2025

Quasinormal ringing of Kerr black holes. III. Excitation coefficients for equatorial inspirals from the innermost stable circular orbit

The remnant of a black hole binary merger settles into a stationary configuration by "ringing down" through the emission of gravitational waves that consist of a superposition of damped exponentials with discrete complex frequencies - the remnant black hole's quasinormal modes. While the frequencies themselves depend solely on the mass and spin of the remnant, the mode amplitudes depend on the merger dynamics. We investigate quasinormal mode excitation by a point particle plunging from the innermost stable circular orbit of a Kerr black hole. Our formalism is general, but we focus on computing the quasinormal mode excitation coefficients in the frequency domain for equatorial orbits, and we analyze their dependence on the remnant black hole spin. We find that higher overtones and subdominant multipoles of the radiation become increasingly significant for rapidly rotating black holes. This suggests that the prospects for detecting overtones and higher-order modes are considerably enhanced for highly spinning merger remnants.

gr-qc↗

arXiv2025

Gravitational Atom Spectroscopy

Black holes in our Universe are rarely truly isolated, being instead embedded in astrophysical environments such as plasma or dark matter. A particularly intriguing possibility is that light scalar fields form bound states around black holes, producing extended ''clouds'' known as gravitational atoms. When these clouds become sufficiently compact, the spacetime can no longer be described by a vacuum solution of General Relativity. In this regime, one can construct quasi-stationary, spherically symmetric, self-gravitating scalar gravitational-atom configurations. Here, we explore an observationally relevant aspect of these systems by computing their fundamental quasi-normal mode. We present a fully relativistic calculation of the axial modes in both the time and frequency domains, finding frequency shifts relative to the vacuum case that depends mostly on the compactness of the gravitational atom. For sufficiently compact configurations, these shifts may be detectable by current or future gravitational wave detectors.

gr-qc↗

arXiv2024

Probing time-dependent scalar wigs with extreme mass ratio inspirals

We investigate the gravitational wave emission from extreme mass ratio inspirals, key targets for the upcoming space-based detector LISA, considering the scenario where the lighter black hole in the binary is endowed by a long-lived, time-dependent scalar field configuration, known as a scalar wig. We develop a formalism to compute scalar perturbations for extreme mass ratio inspirals on circular orbits around Schwarzschild and Kerr black holes, and apply this framework to compute additional fluxes induced by the scalar wig as well as their dependence on the scalar field properties. Our computation provides strong indications that in this scenario the presence of the scalar field does not significantly affect the orbital motion and the gravitational waveform.

gr-qc↗

arXiv2024

Black hole spectroscopy in environments: detectability prospects

The ringdown phase following a binary black hole coalescence is a powerful tool for measuring properties of the remnant black hole. Future gravitational wave detectors will increase the precision of these measurements and may be sensitive to the environment surrounding the black hole. This work examines how environments affect the ringdown from a binary coalescence. Our analysis shows that for astrophysical parameters and sensitivity of planned detectors, the ringdown signal is indistinguishable from its vacuum counterpart, suggesting that ringdown-only analyses can reliably extract the (redshifted) mass and spin of the remnant black hole. These conclusions include models with spectral instabilities, suggesting that these are not relevant from an observational viewpoint. Deviations from inspiral-only estimates could then enhance the characterisation of environmental effects present during the coalescence.

gr-qc↗

arXiv2024

Extreme mass-ratio inspirals as probes of scalar fields: inclined circular orbits around Kerr black holes

Extreme mass-ratio inspirals, a target source for the space-based gravitational wave detector LISA, are a sensitive probe of fundamental scalar fields coupled to gravity. We assess the capability of LISA to detect whether the secondary compact object is endowed with a scalar field, in the case of inclined orbits. We show that the imprint of the scalar field depends on the orbital inclination, and is significantly larger for prograde orbits.

gr-qc↗