arXiv subjects

Antonio Enea Romano

Publications and source records attributed to Antonio Enea Romano.

At least 19 recordsLinked to original sources

arXiv2026

The Impact of Galaxy Catalogue Completeness with GLADE+ on Dark Siren Cosmology: A Line-of-Sight Prior Analysis of GWTC-3 Events

Cosmological parameters can be estimated from dark sirens, gravitational waves events without electromagnetic counterpart, by using inference methods which estimate statistically the source redshift from galaxy catalogs. We study the effects of applying different apparent magnitude cuts to the GLADE+ catalog, analyzing events from the third LIGO-Virgo-KAGRA gravitational wave transient catalog (GWTC-3), consisting of 42 binary black holes, 3 neutron star black hole systems and the event GW190425 associated to a binary neutron star coalescence. We find that the inclusion of fainter galaxies has no significant effects on the joint analysis of almost all the events, while for some single well localized event, the effects can be more important, in particular for the event GW190814. To understand why inclusion of fainter galaxies in general has negligible impact on the estimation of cosmological parameters, we compare the redshift of the events with the redshift distribution of dimmer galaxies, and find that most of them are not located in redshift proximity of the events, explaining the limited impact of their inclusion. The event, GW190814 is an exception, as its distance localization, converted into redshift, overlaps with fainter galaxies, unlike what happens for other events, which are farther away. These results show the importance of event localization and catalog depth in determining the impact of catalog completeness on cosmological parameters estimation. To check quantitatively what is the information gained by adding fainter galaxies we have analyzed its impact on the line of sight prior calculation. Based on the results for GW190814 we expect that fainter galaxies will play a more significant role in the estimation of cosmological parameters also for the joint analysis of multiple events, when deeper catalogs will be available.

astro-ph.CO↗

arXiv2026

Effective speed approach for modified scalar field propagation

We study the propagation of a constant-speed Gaussian scalar field wave packet (GWP) in Minkowski space, showing that the energy conditions are violated for superluminal speeds. We then apply the effective speed approach to the GWP propagation, deriving the corresponding effective metric, effective Lagrangian and effective stress-energy tensor, and test the energy conditions defined in terms of the effective metric. We study the nature of the effective source driving the speed modification, and find that it corresponds to a perfect fluid with negative equation of state.

gr-qc↗

arXiv2026

Testing the consistency of gravitational waves and large scale structure constraints on dark energy

Gravitational wave (GW) astronomy has opened a new window on the Universe, allowing to obtain constraints on dark energy and gravity independent from other electromagnetic waves observations, such as large scale structure (LSS). For the purpose of investigating the consistency between different observations the effective field theory (EFT) of dark energy is a useful tool, allowing to derive model and parametrization independent consistency relations (CR) between the effective gravitational constant, the slip parameter, the gravitational and electromagnetic luminosity (EM) distance, and the speed of GWs. We test the constant brading and no-slip CRs, by comparing for the first time the constraints on the effective gravitational coupling obtained from LSS observations with those from GW events with and without electromagnetic counterparts, confirming the validity of the CRs at the current level of experimental uncertainty. The event GW170817 and its electromagnetic counterpart provides a constraint of the effective gravitational constant with an accuracy comparable with LSS constraints, while the analysis of GW events without electromagnetic counterpart are consistent, but do not have a constraining power comparable to LSS observations. Beside allowing to test the consistency between independent observations, the CRs can be used to estimate the effective gravitational coupling with GWs at high redshift, where other observations are not available.

gr-qc↗

arXiv2026

The effects of dark energy on the matter-gravity coupling

Dark energy perturbations are expected to modify the evolution of cosmological perturbations, producing different observational effects. We show that these effects can be encoded in a momentum, space and polarization dependent effective matter-gravity coupling. For scalar perturbations the effective gravitational coupling can be locally negative, in regions with local dark energy under-densities. For adiabatic perturbations the effective gravitational coupling for scalar perturbations can be negative for phantom dark energy, providing a possible explanation for the observed structure suppression at low redshift, consistent with other independent evidences of evolving dark energy. For gravitational waves the effective coupling can make the radiation emitted by compact binary convalescences polarization and frequency dependent.

gr-qc↗

arXiv2026

Testing the consistency of cosmological models with multimessenger astronomy

We show that within the framework of the Friedmann cosmological model it is possible to derive general multimessenger consistency conditions, between the gravitational wave (GW) and the electromagnetic wave (EMW) luminosity distances. We first study the effects of the flatness assumption often used in the estimation of cosmological parameters from GWs observations, deriving a general relation for the curvature parameter, uniquely in terms of the flatness biased GW and the EMW luminosity distances, and a multimessenger consistency relation for the Friedmann model, valid independently of the dark energy equation of state. We then derive a general multimessenger consistency relation for the cosmological constant, which is independent of any flatness assumption made in the analysis of observational data.

gr-qc↗

arXiv2026

Blinded Mock Data Challenge: Is the Spectral Siren Technique Robust for Measuring the Hubble Constant?

The measurement of the Hubble constant from gravitational wave (GW) sources is one of the independent avenues to shed light on the Hubble tension, which is associated with about an $8\%$ mismatch in the value of the Hubble constant inferred from low-redshift and high-redshift cosmological probes. Such a key measurement is expected from GW sources as it is a direct measurement of the Hubble constant using the luminosity distance without the need for any luminosity distance calibration. However, such a measurement relies strongly on the reliability of the independent inference of the source redshift of the GW source. As a result, it becomes pertinent to gauge the accuracy and precision of techniques in understanding their reliability in inferring redshifts of GW sources. In this work, we show the requirement of the spectral siren technique in knowing the mass distribution of BBHs across cosmic redshifts in order to make a reliable inference of the Hubble constant. We show by a blinded mock data challenge analysis the criticality in capturing the underlying metallicity dependence of the BBH mass distribution and its interplay with time-delay distribution for a robust inference of the Hubble constant using the spectral siren technique. In order to have a reliable measurement of the Hubble constant at the level required to resolve the Hubble tension in the future, the mass distribution of the BBHs needs to be independently inferred at all relevant redshifts with an accuracy less than the statistical uncertainty. Otherwise, a mismatch of the true model and the underlying assumption made in the analysis can lead to a best-fit model for the wrong value of both BBH population parameters as well as the Hubble constant.

astro-ph.CO↗

arXiv2026

Non parametric constraints of gravitational-electromagnetic luminosity distance ratio

The ratio between the gravitational waves (GW) and electromagnetic waves (EMW) luminosity distance ratio is a key observable that allows to test the nature of gravity, using gravitational waves emitted from compact binary coalescences. We develop a new non parametric method for constraining the GW-EMW distance ratio, in order to perform model independent analysis of observational data, not based on any specific theoretical of phenomenological assumption. We apply the method to the analysis of binary black hole mergers data from the GWTC-3 catalogue, performing a joint analysis of cosmological and population parameters. The results are consistent with general relativity and with previous analyses based on parametric methods.

gr-qc↗

arXiv2025

Multimessenger consistency relations bridging gravitational wave and large scale structure observations

We show that for Horndeski theories it is possible to derive mathematically compact consistency relations (CR) between physically observable quantities, valid for different classes of theories defined by the behavior of the brading function $α_B$, independent of all other property functions. The CRs establish a parametrization independent direct relation between the effective gravitational constant, the slip parameter, the gravitational and electromagnetic waves (EMW) luminosity distances, the speed of gravitational waves (GW) and the sound speed. The no-brading CR is also satisfied by general relativity (GR), and allows to estimate the gravitational coupling from GWs observations, independently from large scale structure (LSS) observations. A general, less mathematically compact, consistency condition is also derived, valid for any form of the function $α_B$ and the other property functions. We apply the CRs to map the large scale structure observational constraints on the effective gravitational constant and the slip parameter to GW-EMW distance ratio constraints, showing that LSS and GWs give independent constraints consistent with no-brading. Beside allowing to perform parametrization and model independent tests of the consistency between different constraints on modified gravity, the CRs allow to probe the value of the effective gravitational constant with multimessenger observations, independently from LSS observations.

gr-qc↗

arXiv2025

The Effects of the Gravitational Coupling Variation on the Local $H_0$ Estimation

We study the effects of the time evolution of the matter-gravity coupling on the luminosity distance, showing it can provide a natural explanation to the apparent Hubble tension. The gravitational coupling evolution induces a modification of the Friedman equation with respect to the $Λ$CDM model, which we study in both the Einstein and Jordan frame. We consider a phenomenological parametrization of the low redshift variation of the coupling in a narrow redshift shell, showing how it can affect the distance of the anchors used to calibrate supernovae (SNe), while higher redshift background observations are not affected. This effect is purely geometrical, and it is not related to any change of the intrinsic SNe physical properties. The effects of a time varying gravity coupling only manifest on sufficiently long time scales, such as in cosmological observations at different redshifts, and if ignored lead to apparent tensions in the values of cosmological parameters estimated with observations from different epochs of the Universe history.

gr-qc↗

arXiv2025

Blinded Mock Data Challenge for Gravitational-Wave Cosmology-I: Assessing the Robustness of Methods Using Binary Black Holes Mass Spectrum

Gravitational Wave (GW) sources are standard sirens that provide an independent way to map the cosmic expansion history by combining with an independent redshift measurement either from an electromagnetic counterpart for a bright siren or using different statistical techniques for dark sirens. In this analysis, we perform the first Blinded Mock Data Challenge (\texttt{Blinded-MDC}) to test the robustness in inferring the value of Hubble constant $H_0$ for a dark siren technique which depends on astrophysical mass distribution of Binary Black Holes (BBHs). We have considered different analysis setups for the \texttt{Blinded-MDC} to test both statistical and systematic uncertainties and demonstrate the capabilities in inferring $H_0$ with detector sensitivity as per the fourth observation run of LIGO-Virgo-KAGRA. We find that when the astrophysical population of BBHs matches with the underlying assumption of the model, a cosmological pipeline can recover the injected parameters using the observed mass distribution. However, when the mock mass distribution of the astrophysical population depends slightly on redshift and one is ignorant about it in analyzing the data, it can cause a systematic discrepancy in the inferred value of $H_0$ by about $1.5σ$, above the statistical fluctuations due to noise and a limited number of events. In the future, elaborate studies will be required to mitigate systematic uncertainties due to unknown astrophysical complexities. This MDC framework sets the road map for inspecting the precision and accuracy of standard siren cosmology and provides the first insight into the robustness of the population-dependent cosmology inference in a blinded analysis setup.

astro-ph.CO↗

arXiv2025

Constraining the effective field theory of dark energy with multimessenger astronomy

The effective field theory of dark energy predicts a possible time variation of the propagation speed of gravitational waves (GW) which could be tested with multimessenger astronomy. For this purpose we derive the relation between the redshift dependence of the propagation speed of GWs and the time delay between the detection of GWs and electromagnetic waves (EMWs) emitted by the same source. According to the EFT the friction term of the GW propagation equation depends on the effective Planck mass and GW speed time variation, affecting the GW-EMW luminosity distance ratio. We compute the general form of the GW-EMW luminosity distance ratio in terms of the effective GW speed and effective Planck mass, and then focus on theories with constant Planck mass (CPM) and time varying GW speed. For CPM theories the GW speed can be jointly constrained by the GW-EMW detection time delay and luminosity distance ratio, allowing to derive a consistency relation between these two observables. The event GW170817 and its EM counterpart satisfy the CPM consistency condition, and allows to set constraints on the time variation of the GWs speed, and consequently on the coefficients of the effective theory.

gr-qc↗

arXiv2024

Primordial black holes from local features of the inflaton potential

Primordial black holes (PBH) can form in the early Universe from peaks of the primordial curvature perturbations. The statistics of the peaks determines the abundance of PBHs, and is related to the amplitude of the primordial curvature spectrum. We study single field inflationary models with local features of the inflaton potential which induce a growth of curvature perturbations on super-horizon scales, which can increase the spectrum, and consequently the predicted PBHs abundance. We compute the effects of the different parameters of the features on the PBHs abundance, giving some example of models compatible with observational constraints. The mechanism is general, and can induce the PBH production in diffent mass ranges by appropriately tuning the parameters, and we give a specific example producing PBHs with abundance compatible with asteroid mass constraints.

astro-ph.CO↗

arXiv2024

Effective speed of cosmological perturbations

We derive an effective equation and action for comoving curvature perturbations and gravitational waves (GWs) in terms of a time, momentum and polarization dependent effective speed, encoding the effects of the interaction among metric perturbations or with other fields, such as dark energy and dark matter. The structure of the effective actions and equations is the same for scalar and tensor perturbations, and the effective actions can be written as the Klein-Gordon action in terms of an appropriately defined effective metric, dependent on the effective speed. The effective action reproduces, and generalizes to higher order in perturbations, results obtained for GWs in the effective field theory of inflation and dark energy, or for curvature perturbations in systems with multiple scalar fields, encoding in the effective speed the effects of both entropy and anisotropy. The effective approach can also be applied to the solutions of theories with field equations different from the Einstein equations, by defining an appropriate effective energy-momentum tensor. As an example, we show that for a minimally coupled scalar field in general relativity, the effective speeds of curvature perturbations and gravitational waves are frequency and polarization dependent, due to their coupling in the action beyond the quadratic order.

gr-qc↗

arXiv2024

Gravitoelectromagnetic quadrirefringence

We develop an effective approach for the study of the interaction of gravitational waves (GWs) and electromagnetic waves (EMWs), showing that quadrirefringence can be produced, a phenomenon consisting in a frequency and polarization dependency of the speed of the different polarizations of GWs and EMWs, which is also inducing a frequency and polarization dependent modification of the GW-EMW luminosity distance ratio. Quadrirefringence can be due to the GW-EMW interaction in the source or during the propagation from the source to the observer. In the first case the astrophysical properties of the source can induce a unique characteristic imprint on GWs and EMWs for each source, the rainbow of binaries, while the effect on the propagation from the source could be used to probe the large scale electromagnetic field using GWs. Numerical general relativistic magnetohydrodynamic (GRMHD) simulations can be used to obtain precise theoretical predictions for different binary systems with large electromagnetic and gravitational fields, such as binary neutron stars.

gr-qc↗

arXiv2024

Probing the dark Universe with gravitational waves

Gravitational waves (GW) are expected to interact with dark energy and dark matter, affecting their propagation on cosmological scales. In order to model this interaction, we derive a gauge invariant effective equation and action valid for all GWs polarizations, based on encoding the effects of the interaction of GWs at different order in perturbations, in a polarization, frequency and time dependent effective speed. The invariance of perturbations under time dependent conformal transformations and the gauge invariance of the GWs allow to obtain the unitary gauge effective action in any conformally related frame, making transparent the relation between Einstein and Jordan frame. The propagation time and luminosity distance of different GWs polarizations allow to probe at different frequencies and redshift the dark Universe, which act as an effective medium, whose physical properties can be modeled by the GWs effective speed.

astro-ph.CO↗

arXiv2024

Effective speed of gravitational waves

We derive an effective equation and action for the propagation of gravitational waves (GW), encoding the effects of interaction and self-interaction in a time, frequency and polarization dependent effective speed. In terms of an appropriately defined effective metric, the effective action takes the form a massless Klein-Gordon action. This effective approach predicts that for theories with matter coupled to the Einstein frame metric the ratio between gravitational and electromagnetic (EM) luminosity distance depends on the effective speed, while for Jordan frame matter coupling it depends on the effective Planck mass. We discuss how the frequency and polarization dependence of the GW-EM distance ratio provides a new test of general relativity and its modifications, and more in general of the interaction of GWs with other fields.

gr-qc↗

arXiv2023

Joint cosmological and gravitational-wave population inference using dark sirens and galaxy catalogues

In the absence of numerous gravitational-wave detections with confirmed electromagnetic counterparts, the "dark siren" method has emerged as a leading technique of gravitational-wave cosmology. The method allows redshift information of such events to be inferred statistically from a catalogue of potential host galaxies. Due to selection effects, dark siren analyses necessarily depend on the mass distribution of compact objects and the evolution of their merger rate with redshift. Informative priors on these quantities will impact the inferred posterior constraints on the Hubble constant ($H_0$). It is thus crucial to vary these unknown distributions during an $H_0$ inference. This was not possible in earlier analyses due to the high computational cost, restricting them to either excluding galaxy catalogue information, or fixing the gravitational-wave population mass distribution and risking introducing bias to the $H_0$ measurement. This paper introduces a significantly enhanced version of the Python package GWCOSMO, which allows joint estimation of cosmological and compact binary population parameters. This thereby ensures the analysis is now robust to a major source of potential bias. The gravitational-wave events from the Third Gravitational-Wave Transient Catalogue are reanalysed with the GLADE+ galaxy catalogue, and an updated, more reliable measurement of $H_0=69^{+12}_{-7}$ km s$^{-1}$ Mpc$^{-1}$ is found (maximum a posteriori probability and 68% highest density interval). This improved method will enable cosmological analyses with future gravitational-wave detections to make full use of the information available (both from galaxy catalogues and the compact binary population itself), leading to promising new independent bounds on the Hubble constant.

astro-ph.CO↗

arXiv2023

The mirage of luminal modified gravitational-wave propagation

Using conformal invariance of gravitational waves, we show that for a luminal modified gravity theory, the gravitational-wave propagation and luminosity distance are the same as in general relativity. The relation between the gravitational-wave and electromagnetic-wave luminosity distance gets however modified for electromagnetism minimally coupled to the Jordan frame metric. Using effective field theory we show that the modified relation obtained for luminal theories is also valid for non-luminal theories with Jordan frame matter-gravity coupling.We generalise our analysis to a time-dependent speed of gravitational waves with matter minimally coupled to either the Jordan or Einstein frame metrics.

gr-qc↗