arXiv subjects

Marco Muccino

Publications and source records attributed to Marco Muccino.

At least 37 records · Page 2Linked to original sources

arXiv2025

Geometric properties versus particle motion in the Fan-Wang spacetime

In this work, we explore general relativistic effects and geometric properties of the Fan-Wang spacetime, one of the simplest regular solutions that can be obtained in nonlinear electrodynamics. In particular, we investigate the motion of test particles, the capture cross-section of neutral massive and massless particles, such as neutrinos and photons, and the gravitational redshift. Additionally, using a perturbative approach, we derive analytical expressions for the perihelion shift and gravitational deflection of massless particles. By identifying the one-parameter corrections to the Schwarzschild spacetime, induced by the magnetic charge contained in the Fan-Wang metric, we show that this spacetime can be falsified, since it modifies classical general relativity predictions even at the local level. Moreover, we argue that these modifications could be experimentally tested with advanced observational instrumentation.

gr-qc↗

arXiv2025

Accretion disk luminosity around rotating naked singularities

We explore circular geodesics of neutral test particles in the gravitational field of a rotating deformed mass. The geometry around this source is described by the Quevedo-Mashhoon solution, which corresponds to a naked singularity. To this end, we compute the orbital parameters of test particles in the equatorial plane, such as the angular velocity $Ω$, energy $E$ and angular momentum $L$, per unit mass. We also numerically estimate the radius of the innermost stable circular orbit $r_{ISCO}$. In addition, we consider a simple model for the disk's radiative flux, differential luminosity, and spectral luminosity, employing the well-known Novikov-Page-Thorne model. We mainly focus on the flux of the accretion disk around several rotating naked singularities possessing the same mass and quadrupole moment but different rotation and deformation parameters. We analyze the possibility of distinguishing Kerr black holes from rotating naked singularities. The astrophysical implications of the results obtained are discussed.

gr-qc↗

arXiv2024

Characterizing the equivalence between dark energy and radiation using gamma-ray bursts

Differently from the equivalence time between either matter and radiation or dark energy and matter, the equivalence between dark energy and radiation occurs between two subdominant fluids, since it takes place in the matter dominated epoch. However, dark energy--radiation equivalence may correspond to a \emph{cosmographic bound} since it strongly depends on how dark energy evolves. Accordingly, a possible model-independent bound on this time would give hints on how dark energy evolves in time. In this respect, gamma-ray bursts (GRBs) may be used, in fact, as tracers to obtain cosmic constraints on this equivalence. Consequently, based on observed GR data from the $E_{\rm p}$--$E_{\rm iso}$ correlation, we here go beyond by simulating additional GRB data points and investigating two distinct equivalence epochs: 1) dark energy--radiation, and 2) dark energy--radiation with matter. We thus extract constraints on the corresponding two redshifts adopting Monte Carlo Markov chain simulations by means of two methods: the first performing the GRB calibration and the cosmological fit steps independently, and the second performing these steps simultaneously by resorting a hierarchical Bayesian regression. To keep the analysis model-independent, we consider a generic dark energy model, with the unique constraint to reduce to the $Λ$CDM at $z=0$. Our findings are thus compared to theoretical predictions, indicating that the $Λ$CDM model is statistically favored to predict such an equivalence time, though a slow evolution with time cannot be fully excluded. Finally, we critically re-examine the Hubble constant tension in view of our outcomes.

astro-ph.CO↗

arXiv2024

Determining $H_0$ from distance sum rule combining gamma-ray bursts with observational Hubble data and strong gravitational lensing

Model-independent bounds on the Hubble constant $H_0$ are important to shed light on cosmological tensions. We work out a model-independent analysis based on the sum rule, which is applied to late- and early-time data catalogs to determine $H_0$. Through the model-independent Bézier interpolation of the observational Hubble data (OHD) and assuming a flat universe, we reconstruct the dimensionless distances of the sum rule and apply them to strong lensing data to derive constraints on $H_0$. Next, we extend this method to the high-redshift domain including, in other two separated analyses, gamma-ray burst (GRB) data sets from the well-established Amati and Combo correlations. In all three analyses, our findings agree at $1σ$ level with the $H_0$ determined from type Ia supernovae (SNe Ia), and only at $2σ$ level with the measurement derived from the cosmic microwave background (CMB) radiation. Our method evidences that the bounds on $H_0$ are significantly affected by strong lensing data, which favor the local measurement from SNe Ia. Including GRBs causes only a negligible decrease in the value of $H_0$. This may indicate that GRBs can be used to trace the expansion history and, in conjunction with CMB measurements, may heal the Hubble tension and accommodate to the flat $Λ$CDM paradigm purported by CMB data.

astro-ph.CO↗

arXiv2024

Dark energy constraints using gamma-ray burst correlations with DESI 2024 data

Even though the Dark Energy Spectroscopic Instrument (DESI) mission does not exclude a dynamical dark energy evolution, the concordance paradigm, i.e., the $Λ$CDM model, remains statistically favored, as it depends on the fewest number of free parameters. In this respect, high redshift astrophysical sources, such as gamma-ray bursts, represent a formidable tool to model the form of dark energy, since they may provide a link between early and local redshift regimes. Hence, the use of these objects as possible distance indicators turns out to be essential to investigate the cosmological puzzle. To this end, we adopt two gamma-ray burst linear correlations, namely the $L_p-E_p$ and $L_0-E_p-T$ relations, to test the flat and non-flat $Λ$CDM, $ω_0$CDM, and $ω_0ω_1$CDM cosmological models, i.e., those directly examined by the DESI collaboration. The inferred correlation coefficients and cosmological parameters are thus obtained by considering two independent Monte Carlo Markov chain analyses, the first considering the whole DESI data set and the second excluding a seemingly problematic data point placed at $z_{eff} = 0.51$. Using model selection criteria, the two above correlations do not show a preference on a precise cosmological model although, when the data point at $z_{eff}$ is included, the concordance paradigm appears to be the least favored among the tested cosmological models.

astro-ph.CO↗

arXiv2024

Dark energy reconstructions combining BAO data with galaxy clusters and intermediate redshift catalogs

Cosmological parameters and dark energy (DE) behavior are generally constrained assuming \textit{a priori} models. We work out a model-independent reconstruction to bound the key cosmological quantities and the DE evolution. Through the model-independent \textit{Bézier interpolation} method, we reconstruct the Hubble rate from the observational Hubble data and derive analytic expressions for the distances of galaxy clusters, type Ia supernovae, and uncorrelated baryonic acoustic oscillation (BAO) data. In view of the discrepancy between Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) BAO data, they are kept separate in two distinct analyses. Correlated BAO data are employed to break the baryonic--dark matter degeneracy. All these interpolations enable us to single out and reconstruct the DE behavior with the redshift $z$ in a totally model-independent way. In both analyses, with SDSS-BAO or DESI-BAO data sets, the constraints agree at $1$--$σ$ confidence level (CL) with the flat $Λ$CDM model. The Hubble constant tension appears solved in favor of the Planck satellite value. The reconstructed DE behavior exhibits deviations at small $z$ ($>1$--$σ$ CL), but agrees ($<1$--$σ$ CL) with the cosmological constant paradigm at larger $z$. Our method hints for a slowly evolving DE, consistent with a cosmological constant at early times.

astro-ph.CO↗

arXiv2024

Cosmological constraints from calibrated $E_p-E_{iso}$ gamma-ray burst correlation by using DESI 2024 data release

Recent outcomes by the DESI Collaboration have shed light on a possible slightly evolving dark energy, challenging the standard $Λ$CDM paradigm. To better understand dark energy nature, high-redshift observations like gamma-ray burst data become essential for mapping the universe expansion history, provided they are calibrated with other probes. To this aim, we calibrate the $E_p-E_{iso}$ (or Amati) correlation through model-independent Bézier interpolations of the updated Hubble rate and the novel DESI data sets. More precisely, we provide two Bézier calibrations: i) handling the entire DESI sample, and ii) excluding the point at $z_{eff}=0.51$, criticized by the recent literature. In both the two options, we let the comoving sound horizon at the drag epoch, $r_d$, vary in the range $r_d \in [138, 156]$ Mpc. The Planck value is also explored for comparison. By means of the so-calibrated gamma-ray bursts, we thus constrain three dark energy frameworks, namely the standard $Λ$CDM, the $ω_0$CDM and the $ω_0ω_1$CDM models, in both spatially flat and non-flat universes. To do so, we worked out Monte Carlo Markov chain analyses, making use of the Metropolis-Hastings algorithm. Further, we adopt model selection criteria to check the statistically preferred cosmological model finding a preference towards the concordance paradigm only whether the spatial curvature is zero. Conversely, and quite interestingly, the flat $ω_0$CDM and both the cases, flat/non-flat, $ω_0ω_1$CDM model, leave evidently open the chance that dark energy evolves at higher redshifts.

astro-ph.CO↗

arXiv2024

Does dark energy really revive using DESI 2024 data?

We investigate the impact of the Dark Energy Spectroscopic Instrument (DESI) 2024 data on dark energy scenarios. We thus analyze three typologies of models, the first in which the cosmic speed up is related to thermodynamics, the second associated with Taylor expansions of the barotropic factor, whereas the third based on \emph{ad hoc} dark energy parameterizations. In this respect, we perform Monte Carlo Markov chain analyses, adopting the Metropolis-Hastings algorithm, of 12 models. To do so, we first work at the background, inferring \emph{a posteriori} kinematic quantities associated with each model. Afterwards, we obtain early time predictions, computing departures on the growth evolution with respect to the model that better fits DESI data. We find that the best model to fit data \emph{is not} the Chevallier-Polarski-Linder (CPL) parametrization, but rather a more complicated log-corrected dark energy contribution. To check the goodness of our findings, we further directly fit the product, $r_d h_0$, concluding that $r_d h_0$ is anticorrelated with the mass. This treatment is worked out by removing a precise data point placed at $z=0.51$. Surprisingly, in this case the results again align with the $Λ$CDM model, \emph{indicating that the possible tension between the concordance paradigm and the CPL model can be severely alleviated}. We conclude that future data points will be essential to clarify whether dynamical dark energy is really in tension with the $Λ$CDM model.

astro-ph.CO↗

arXiv2024

Model independent cosmographic constraints from DESI 2024

In this study, we explore model independent constraints on the universe kinematics up to the snap and jerk hierarchical terms. To do so, we consider the latest Baryon Acoustic Oscillation (BAO) release provided by the DESI collaboration, tackling the $r_d$ parameter to span within the range $[144,152]$ Mpc, with fixed step, $δr_d=2$ Mpc, aligning with Planck and DESI results. Thus, employing Monte Carlo Markov chain analyses, we place stringent constraints on the cosmographic series, incorporating three combinations of data catalogs: the first BAO with observational Hubble data, the second BAO with type Ia supernovae, and the last including all three data sets. Our results conclusively constrain the cosmographic series, say the deceleration $q_0$, the jerk $j_0$, and the snap $s_0$ parameters, at the $2$--$σ$ level, showcasing a significant departure on $j_0$ even at $1$--$σ$ confidence level, albeit being compatible with the $Λ$CDM paradigm on $q_0$ and $s_0$, at $2$--$σ$ level. Analogously, the $h_0$ tension appears alleviated in the second hierarchy, say including snap. Finally, a direct comparison with the $Λ$CDM, $w$CDM models and the Chevallier-Polarski-Linder parametrization is reported, definitively favoring the wCDM scenario.

astro-ph.CO↗

arXiv2024

Double polytropic cosmic acceleration from the Murnaghan equation of state

We consider a double polytropic cosmological fluid and demonstrate that, when one constituent resembles a bare cosmological constant while the other emulates a generalized Chaplygin gas, a good description of the Universe's large-scale dynamics is obtained. In particular, our double polytropic reduces to the Murnaghan equation of state, whose applications are already well established in solid state physics and classical thermodynamics. Intriguingly, our model approximates the conventional $Λ$CDM paradigm while reproducing the collective effects of logotropic and generalized Chaplygin fluids across different regimes. To check the goodness of our fluid description, we analyze first order density perturbations, refining our model through various orders of approximation, utilizing $σ_8$ data alongside other cosmological data sets. Encouraging results suggest that our model, based on the Murnaghan equation of state, outperforms the standard cosmological background within specific approximate regimes and, on the whole, surpasses the standard phenomenological reconstruction of dark energy.

gr-qc↗

arXiv2024

Cosmological transition epoch from gamma-ray burst correlations

The redshift $z_t$ and the jerk parameter $j_t$ of the transition epoch are constrained by using two model-independent approaches involving the direct expansion of the Hubble rate and the expansion of the deceleration parameter around $z=z_t$. To extend our analysis to high-redshifts, we employ the \emph{Amati}, \emph{Combo}, \emph{Yonetoku} and \emph{Dainotti} gamma-ray burst correlations. The \textit{circularity problem} is prevented by calibrating these correlations through the Bézier interpolation of the updated observational Hubble data. Each gamma-ray burst data set is jointly fit with type Ia supernovae and baryonic acoustic oscillations through a Monte Carlo analysis, based on the Metropolis-Hastings algorithm, to obtain $z_t$, $j_t$ and the correlation parameters. The overall results are compatible with the concordance model with some exceptions. We also focus on the behaviors of the dark energy, verifying its compatibility with a cosmological constant, and the matter density $Ω_m$ and compare them with the expectations of the concordance paradigm.

astro-ph.CO↗

arXiv2024

Equivalence principle violation in nonminimally coupled gravity and constraints from Lunar Laser Ranging

We analyze the dynamics of the Sun-Earth-Moon system in the context of a particular class of theories of gravity where curvature and matter are nonminimally coupled (NMC). These theories can potentially violate the Equivalence Principle as they give origin to a fifth force and a extra non-Newtonian force that may imply that Earth and Moon fall differently towards the Sun. We show, through a detailed analysis, that consistency with the bound on Weak Equivalence Principle arising from 48 years of Lunar Laser Ranging data, for a range of parameters of the NMC gravity theory, can be achieved via the implementation of a suitable screening mechanism.

gr-qc↗

arXiv2023

Quasi-periodic oscillations in rotating and deformed spacetimes

Quasi-periodic oscillation (QPOs) analysis is important for understanding the dynamical behavior of many astrophysical objects during transient events such as gamma-ray bursts, solar flares, magnetar flares, and fast radio bursts. In this paper, we analyze QPO data in low-mass X-ray binary (LMXB) systems, using the Lense-Thirring, Kerr, and approximate Zipoy-Voorhees metrics. We demonstrate that the inclusion of spin and quadrupole parameters modifies the well-established results for the fundamental frequencies in the Schwarzschild spacetime. We interpret the QPO data within the framework of the standard relativistic precession model, allowing us to infer the values of the mass, spin, and quadrupole parameters of neutron stars in LMXBs. We explore recent QPO data sets from eight distinct LMXBs, assess their optimal parameters, and compare our findings with results in the existing literature. Finally, we discuss the astrophysical implications of our findings.

astro-ph.HE↗

arXiv2023

Breaking the baryon-dark matter degeneracy in a model-independent way through the Sunyaev-Zeldovich effect

We propose a model-independent \textit{Bézier parametric interpolation} to alleviate the degeneracy between baryonic and dark matter abundances by means of intermediate-redshift data. To do so, we first interpolate the observational Hubble data to extract cosmic bounds over the (reduced) Hubble constant, $h_0$, and interpolate the angular diameter distances, $D(z)$, of the galaxy clusters, inferred from the Sunyaev-Zeldovich effect, constraining the spatial curvature, $Ω_k$. Through the so-determined Hubble points and $D(z)$, we interpolate uncorrelated data of baryonic acoustic oscillations bounding the baryon ($ω_b = h^2_0Ω_b$) and total matter ($ω_m = h^2_0Ω_m$) densities, reinforcing the constraints on $h_0$ and $Ω_k$ with the same technique. Instead of pursuing the usual treatment to fix $ω_b$ via the value obtained from the cosmic microwave background to remove the matter sector degeneracy, we here interpolate the acoustic parameter from correlated baryonic acoustic oscillations. The results of our Monte Carlo--Markov chain simulations turn out to agree at $1$--$σ$ confidence level with the flat $Λ$CDM model. While our findings are roughly suitable at $1$--$σ$ with its non-flat extension too, the Hubble constant appears in tension up to the $2$--$σ$ confidence level. Accordingly, we also reanalyze the Hubble tension with our treatment and find our expectations slightly match local constraints.

astro-ph.CO↗

arXiv2023

Unifying the dark sector through a single matter fluid with non-zero pressure

We explore a generalised unified dark energy model that incorporates a non-minimal interaction between a tachyonic fluid and an additional scalar field. Specifically, we require that the second field possesses a vacuum energy, introducing an ineliminable offset due to a symmetry-breaking mechanism. After the transition (occurring as due to the symmetry-breaking mechanism of the second field), the corresponding equation of state (EoS) takes the form of a combination between a generalised Chaplygin gas (GCG) component and a cosmological constant contribution. We reinterpret this outcome by drawing parallels to the so-called Murnaghan EoS, widely-employed in the realm of solid-state physics to characterise fluids that, under external pressure, counteract the pressure's effect. We examine the dynamic behaviour of this model and highlight its key distinctions compared to the GCG model. We establish parameter bounds that clarifies the model's evolution across cosmic expansion history, showing that it, precisely, exhibits behaviour akin to a logotropic fluid that eventually converges to the $Λ$CDM model in the early universe, while behaving as a logotropic or Chaplygin gas at intermediate and late times respectively. We explain our findings from a thermodynamic perspective, and determine the small perturbations in the linear regime. At very early times, the growth factor flattens as expected while the main departures occur at late times, where the Murnagham EoS results in a more efficient growth of perturbations. We discuss this deviation in view of current observations and conclude that our model is a suitable alternative to the standard cosmological paradigm, introducing the concept of a matter-like field with non-zero pressure.

gr-qc↗

arXiv2023

Luminosity of accretion disks around rotating regular black holes

We consider thin accretion disks in the field of a class of rotating regular black holes. For this purpose, we obtain the radius of the innermost stable circular orbit, $r_{ISCO}$ and efficiency of accretion disk in converting matter into radiation $η$ with the aim of modeling the disk's emission spectrum. We consider a simple model for the disk's radiative flux, differential and spectral luminosity and compare the results with those expected from accretion disks around Kerr black holes. As a remarkable result, from our computations we find that both the luminosity of the accretion disk and the efficiency are larger in the geometry of rotating regular black holes for fixed and small values of the spin parameter $j$ with respect to those predicted with the Kerr metric for a black hole of the same mass. These results may have interesting implications for astrophysical black holes.

gr-qc↗

arXiv2023

Constraints on the transition redshift from the calibrated Gamma-ray Burst $E_{\rm p}$-$E_{\rm iso}$ correlation

We constrain the deceleration-acceleration epoch, namely the transition redshift $z_{tr}$, adopting model-independent techniques that utilize a calibrated $E_{\rm p}$-$E_{\rm iso}$ correlation for gamma-ray bursts (GRBs). To do so, in addition to real data points, we employ up to $1000$ simulated observational Hubble data (OHD) points. We then calibrate the $E_{\rm p}$-$E_{\rm iso}$ correlation by means of the well-consolidate Bézier polynomial technique, interpolating OHD up to the second order. Once GRB data have been calibrated, we consider two strategies of cosmographic expansions, i.e., first we take a direct Hubble rate expansion around $z_{tr}$, and second the expansion of the deceleration parameter around the same redshift, but with a different order. Employing type Ia supernovae, baryonic acoustic oscillations and GRB data sets, from Monte Carlo analyses we infer tight constraints on $z_{tr}$ and the jerk parameters at $z=z_{tr}$, namely $j_{tr}$. Our results are extremely compatible with previous outcomes and confirm the $Λ$CDM predictions, being slightly different in terms of the jerk parameter. In this respect, we conjecture which extensions of the concordance paradigm are possible and we compare our findings with expectations provided by generic dark energy models.

astro-ph.CO↗

arXiv2023

Accretion disk in the Hartle-Thorne spacetime

We consider the circular motion of test particles in the gravitational field of a rotating deformed object described by the Hartle-Thorne metric. This metric represents an approximate solution to the vacuum Einstein field equations, accurate to second order in the angular momentum $J$ and to first order in the mass quadrupole moment $Q$. We calculate the orbital parameters of neutral test particles on circular orbits (in accretion disks) such as angular velocity, $Ω$, total energy, $E$, angular momentum, $L$, and radius of the innermost stable circular orbit, $R_{ISCO}$, as functions of the total mass, $M$, spin parameter, $j=J/M^2$ and quadrupole parameter, $q=Q/M^3$, of the source. We use the Novikov-Thorne-Page thin accretion disk model to investigate the characteristics of the disk. In particular, we analyze in detail the radiative flux, differential luminosity, and spectral luminosity of the accretion disk, which are the quantities that can be measured experimentally. We compare our results with those obtained in the literature for the Schwarzschild and Kerr metrics, and the $q$-metric. It turns out that the Hartle-Thorne metric and the Kerr metric lead to similar results for the predicted flux and the differential and spectral luminosities, whereas the q-metric predicts different values. We compare the predicted values of $M$, $j$, and $q$ with those of realistic neutron star models. Furthermore, we compare the values of $R_{ISCO}$ with the static and rotating radii of neutron stars.

gr-qc↗