arXiv subjects

R. F. L. Holanda

Publications and source records attributed to R. F. L. Holanda.

At least 19 recordsLinked to original sources

arXiv2026

Tracing the Evolution of $Ω_m(z)$ over the Last 10 Billion Years with Non-parametric Methods

We investigate the redshift evolution of the matter density parameter, $Ω_m(z)$, using galaxy cluster gas mass fraction measurements combined with cosmic chronometer $H(z)$ data and type Ia supernova luminosity distances. This provides a non-parametric probe of the normalization of the cosmological matter sector, which plays a central role in current tensions involving weak lensing measurements, cluster abundance analyses, and the $S_8$ parameter. Using Gaussian Process regression, we reconstruct $Ω_m(z)$ without assuming a parametric form for its evolution. The reconstructed evolution is consistent with the standard $ρ_m \propto (1+z)^3$ scaling predicted by the $Λ$CDM model. We obtain $Ω_{m0}=0.296 \pm 0.044$ from the 44-cluster sample, and $Ω_{m0}=0.271 \pm 0.016$, $0.253 \pm 0.017$, and $0.210 \pm 0.013$ for the 103-cluster compilation, depending on the adopted mass calibration. While the reconstructed $Ω_m(z)$ evolution remains consistent with the expected $Λ$CDM behaviour, the inferred normalization of $Ω_{m0}$ depends strongly on the adopted cluster mass calibration. Consequently, cluster mass calibration systematics constitute the dominant source of uncertainty in the inferred normalization of $Ω_{m0}$, exceeding the statistical uncertainties of the non-parametric reconstruction.

astro-ph.CO↗

arXiv2026

Investigating a Possible Variation of the Gravitational Constant Through Gas Mass Fraction Measurements and Type Ia Supernovae Observations

In this paper, we investigate a possible time variation of the gravitational constant (G) using a non-parametric approach. Our main cosmological probe is the gas mass fraction of galaxy clusters measured from X-ray observations. We also account for the effect of a varying $G$ on the intrinsic luminosity of type Ia supernovae (SNe Ia) through the Chandrasekhar mass-luminosity relation. We consider a specific phenomenological scenario, motivated by some scalar-tensor and screened modified-gravity frameworks, in which the standardized luminosity of SNe Ia decreases with increasing Chandrasekhar mass. Using gas mass fraction measurements jointly with luminosity distances from the Pantheon+ compilation, we reconstruct the evolution of G through Gaussian Processes. Our results indicate that a constant gravitational coupling remains broadly consistent with the data, although mild low-redshift departures are allowed.

astro-ph.CO↗

arXiv2026

Revisiting the Constancy of the Speed of Light: Galaxy Cluster Mass Bias Implications

In recent years, improvements in galaxy cluster observations have enabled a variety of tests of fundamental physics using these systems. In this work, we test the constancy of the speed of light, $c$, by combining X-ray gas mass fraction measurements from galaxy clusters with SNe Ia luminosity distance measurements from Pantheon+. We adopt the SH0ES prior on $H_0$ and the $Ω_b/Ω_m$ ratio from galaxy clustering observations, thereby minimizing the dependence of our analysis on any specific cosmological model. We explore different assumptions for the cluster mass calibration (mass bias), including \textsc{CLASH}, \textsc{CCCP}, and Planck-based estimates. We find no deviation from a constant $c$ when adopting \textsc{CLASH} or \textsc{CCCP} priors, while Planck-based calibration yields a mild tension, with the hypothesis of constant $c$ being only marginally consistent at the $2σ$ level, indicating a non-negligible sensitivity of the results to the adopted calibration scheme.

astro-ph.CO↗

arXiv2025

An investigation of a varying G through Strong Lensing and SNe Ia observations

In this paper, we analyze the potential variation of the gravitational constant $G$ using data from strong gravitational lensing systems and Type Ia supernovae. Testing $G(z)$ parameterizations where $G(z) = G_0(1 + G_1z)$ and $G(z) = G_0(1 + z)^{G_1}$, we also account for the influence of $G$ on the luminosity of SNe Ia through the Chandrasekhar mass-luminosity relation. Only the flat universe hypothesis is considered. Constraints from 158 lensing systems and the Pantheon+ sample show no significant evidence of $G$ variation. However, although the results are compatible with no variation, the errors are not yet sufficiently restrictive to rule out any variation of $G$ with high statistical confidence. This study highlights the viability of using combined astrophysical data to probe variations in fundamental constants, suggesting that future surveys could refine these constraints.

astro-ph.CO↗

arXiv2025

Revisiting the temperature evolution law of the CMB with gaussian processes

In this work, we perform a statistical inference of the classical background law governing the evolution of the temperature of the cosmic microwave background radiation (CMB), given by $T_{\rm CMB}(z) = T_0(1 + z)$. To this end, we employ Gaussian Process (GP) regression techniques to reconstruct the temperature evolution based on two observational datasets: (i) CMB-Sunyaev-Zel'dovich (SZ) cluster measurements and (ii) CMB-interstellar medium (ISM) interaction data. Our analysis reveals interesting results that may suggest potential deviations from the standard temperature-redshift relation, particularly at low redshifts ($z < 0.5$), where discrepancies up to $\sim$2$σ$ are observed. Additionally, we identify a mild but noteworthy tension, also at the $\sim$2$σ$ level, between our GP inferred value of the present-day CMB temperature, $T_{\rm CMB}(z=0)$, and the precise direct measurement from the COBE/FIRAS experiment. We also explore possible phenomenological implications of our findings, including interpretations associated with possible variations in fundamental constants, such as the fine-structure constant $α$, which could provide a physical explanation for the observed deviations at low redshift.

astro-ph.CO↗

arXiv2025

A Joint Analysis of Strong Lensing and Type Ia Supernovae to Determine the Hubble Constant

We present a cosmological model-independent determination of the Hubble constant, $H_0$, by combining time-delay measurements from seven TDCOSMO systems, Einstein radius measurements, and Type Ia Supernovae data sourced from the Pantheon+ sample. For each lens of time-delay system, we calculate the angular diameter distance $D_{A_l}$ using the product $D^{\textrm{Obs}}(z_l) \cdot D_{A,Δt}^{\textrm{Obs}}(z_l, z_s)$, where $D^{\textrm{Obs}}(z_l)$ is reconstructed via Gaussian Processes from 99 Einstein radius measurements, and $D_{A,Δt}^{\textrm{Obs}}(z_l,z_s)$ is the time-delay angular distance. We also reconstruct the unanchored luminosity distance $H_0 D_L(z_l)$ from supernova data. By using the cosmic distance duality relation validity, we anchor $D_{A_l}$ and $H_0 D_L(z_l)$ to infer $H_0 = 70.55 \pm 7.44$ km/s/Mpc (68\% CL). Our result, though not resolving the Hubble tension, offers a cosmological model-independent consistency check and highlights the potential of using strong lensing and supernovae data via the cosmic distance duality relation to constrain $H_0$.

astro-ph.CO↗

arXiv2025

Brazilian Report on Dark Matter 2024

One of the key scientific objectives for the next decade is to uncover the nature of dark matter (DM). We should continue prioritizing targets such as weakly-interacting massive particles (WIMPs), Axions, and other low-mass dark matter candidates to improve our chances of achieving it. A varied and ongoing portfolio of experiments spanning different scales and detection methods is essential to maximize our chances of discovering its composition. This report paper provides an updated overview of the Brazilian community's activities in dark matter and dark sector physics over the past years with a view for the future. It underscores the ongoing need for financial support for Brazilian groups actively engaged in experimental research to sustain the Brazilian involvement in the global search for dark matter particles

hep-ph↗

arXiv2025

Observational bounds on a possible electron-to-proton mass ratio variation and constraints in the lepton-specific 2HDM

In this work, we test a possible redshift variation of the electron-to-proton mass ratio, $μ= m_e/m_p$, directly from galaxy cluster gas mass fraction measurements and type Ia supernovae observations. Our result reveals no variation of $μ$ within 1~$σ$. From the point of view of Particle Physics, we can use the precision on these results to constrain the parameter space of models beyond the Standard Model of electroweak interactions. We exemplify this by focusing on a specific Two-Higgs doublet model (2HDM), where the second scalar doublet couples exclusively to leptons. An important parameter in the model concerns the ratio between its vacuum expectation values, defined by $\tanβ\equiv v_2/v_1$. In our approach, we can constrain the inverse parameter $(\cotβ)$ to an optimal value, $(\cotβ)= (2.003 \pm 0.081)\cdot 10^{-3}$, with the highest vacuum expectation value for 2HDM, $v_2$, estimated at around $240.57 \pm 2.93$~GeV. Also, by taking into account the discrepancy in the anomalous magnetic moment of the muon found between theory and experiment, we can reduce the validity region for this model and establish bounds on the scalar masses, in light of our findings from galaxy cluster data for $μ$. This study contributes valuable insights to the understanding of the interface between Particle Physics and Astrophysics, establishing a new interrelationship between data on the large-scale structure of the Universe and subatomic Physics.

hep-ph↗

arXiv2024

Non-Parametric Analysis for the Dark Matter Density Evolution

In this paper, we investigate a potential departure in the standard dark matter density evolution law, $ρ_{dm} = ρ_{dm,0}(1+z)^3$. The method involves considering a deformed evolution model, denoted as $ρ_{dm} = ρ_{dm,0}(1+z)^3f(z)$, and searching the presence of any deviation ($f(z)\neq 1$). As one may see, $f(z)$ is a general function that parametrizes a possible digression from the standard law. We use data of baryon acoustic oscillations, type I Supernovae luminosity distances, and galaxy cluster gas mass fraction observations to reconstruct $f(z)$ through an approach that is not dependent on the cosmological model or the so-called Gaussian process regression. Unlike previous works, it enables us to investigate a possible deviation without using a specific function to describe it. We have obtained $f(z)=1$, the standard model scenario, within $2σ$ c.l. in all the considered cases.

astro-ph.CO↗

arXiv2024

A Hubble Constant Estimate from Galaxy Cluster and type Ia SNe Observations

In this work, we constrain the Hubble constant parameter, $H_0$, using a combination of the Pantheon sample and galaxy clusters (GC) measurements from minimal cosmological assumptions. Assuming the validity of the cosmic distance duality relation, an estimator is created for $H_0$ that only depends on simple geometrical distances, which is evaluated from Pantheon and a GC angular diameter distance sample afterward. The statistical and systematic errors in GC measurements are summed in quadrature in our analysis. We find $H_0 = 67.22 \pm 6.07$ ${\rm km \ s^{-1} Mpc^{-1}}$ in $1σ$ confidence level (C.L.). This measurement presents an error of around 9\%, showing that future and better GC measurements can shed light on the current Hubble tension

astro-ph.CO↗

arXiv2024

Interaction in the dark sector: a phenomenological approach

The non-gravitational interaction between the dark components of the Universe could lead to the variation of dark matter energy density standard evolution law. When we assume this scenario, the dark matter energy density follows $ρ_{dm}\sim(1+z)^{3 + ε(z)}$ (where $ε(z)=0$ the standard law is recovered). In this paper, we perform a Bayesian analysis to test three parameterizations for $ε(z)$, namely: $ε(z)=ε_0$, $ε(z)=ε_0 + ε_1\frac{z}{1+z}$ and $ε(z)=ε_0 + ε_1\frac{z(1+z)}{1+z^2}$, where the first one is motivated through the fundamental grounds and the others are on the phenomenological ones. Through the Gaussian process regression, our method uses galaxy cluster gas mass fraction measurements, SNe Ia observations, Cosmic Chronometers, and BAO data. No specific cosmological model is considered. In all possibilities analyzed, the standard evolution law ($ε(z)=0$) is within $2σ$ c.l. The investigated cases generally indicated scenarios of inconclusive or weak evidence toward the simplest model from the Bayesian standpoint.

astro-ph.CO↗

arXiv2023

Forecasts analysis on varying-$α$ theories from gravitational wave standard sirens

Motivated by future gravitational waves observations, we perform forecasts analysis to constrain a possible time variation of the fine structure constant ($α$) within the context of the so-called runaway dilaton model. For this purpose, some gravitational-wave standard sirens mock data within the perspective of Einstein Telescope and LISA mission were considered jointly with current strong gravitational lensing systems observations. We find that future standard sirens observations can also play an important role in the search for possible variations of $α$ within the methodology presented in this work.

astro-ph.CO↗

arXiv2023

The Hubble constant from galaxy cluster scaling-relation and SNe Ia observations: a consistency test

In this paper, we propose a self-consistent test for a Hubble constant estimate using galaxy cluster and type Ia supernovae (SNe Ia) observations. The approach consists, in a first step, of obtaining the observational value of the galaxy cluster scaling-relation $Y_{SZE}D_{A}^{2}/C_{XSZ}Y_X = C $ by combining the X-Ray and SZ observations of galaxy clusters at low redshifts ($z < 0.1$) from the first {\it Planck mission} all-sky data set ($0.044 \leq z \leq 0.444$), along with SNe Ia observations and making use of the cosmic distance duality relation validity. Then, by considering a flat $Λ$CDM model for $D_A$, the constant $C$ from the first step and the Planck prior on $Ω_M$ parameter, we obtain $H_0$ by using the galaxy cluster data with $z>0.1$. As a result, we obtain $H_0 = 73.014^{+7.435}_{-6.688}$ km/s/Mpc, which represents $9.7\%$ accuracy measurement on the Hubble constant.. We also compare our method with that one where the $C$ parameter is obtained from hydrodynamical simulations of massive galaxy clusters.

astro-ph.CO↗

arXiv2022

Observational constraints on varying fundamental constants in a minimal CPC model

A minimal model based on the Co-varying Physical Couplings (CPC) framework for gravity is proposed. The CPC framework is based on the assumptions of a metric-compatible four-dimensional Riemannian manifold where a covariantly conserved stress-energy tensor acts as source of the field equations which are formally the same as Einstein field equations, but where the couplings $\{ G, c,Λ\}$ are allowed to vary simultaneously. The minimal CPC model takes $Λ$ as a genuine constant while $c$ and $G$ vary in an entangled way that is consistent with Bianchi identity and the aforementioned assumptions. The model is constrained using the most recent galaxy cluster gas mass fraction observational data. Our result indicates that the functions $c(z)$ and $G\left(z\right)=G_{0}\left(c/c_{0}\right)^{4}$ are compatible with constant couplings for the three different parameterizations of $c=c(z)$ adopted here.

gr-qc↗

arXiv2022

Testing a varying-$Λ$ model for dark energy within Co-varying Physical Couplings framework

The Co-varying Physical Couplings (CPC) framework is a modified gravity set up assuming Einstein Field Equations wherein the quantities $\{G,c,Λ\}$ are promoted to space-time functions. Bianchi identity and the requirement of stress-energy tensor conservation entangle the possible variations of the couplings $\{G,c,Λ\}$, which are forced to co-vary as dictated by the General Constraint (GC). In this paper we explore a cosmological model wherein $G$, $c$ and $Λ$ are functions of the redshift respecting the GC of the CPC framework. We assume a linear parametrization of $Λ$ in terms of the scale factor $a$. We use the ansatz $\dot{G}/G = σ\left( \dot{c}/c \right)$ with $σ=$ constant to deduce the functional forms of $c=c(z)$ and $G=G(z)$. We show that this varying-$\{G,c,Λ\}$ model fits SNe Ia data and $H(z)$ data with $σ= 3$. The model parameters can be constrained to describe dark energy at the background level.

gr-qc↗

arXiv2022

A test of the evolution of gas depletion factor in galaxy clusters using strong gravitational lensing systems

In this letter, we discuss a new method to probe the redshift evolution of the gas depletion factor, i.e. the ratio by which the gas mass fraction of galaxy clusters is depleted with respect to the universal mean of baryon fraction. The dataset we use for this purpose consists of 40 gas mass fraction measurements measured at $r_{2500}$ using Chandra X-ray observations, strong gravitational lensing sub-samples obtained from SLOAN Lens ACS + BOSS Emission-line Lens Survey (BELLS) + Strong Legacy Survey SL2S + SLACS. For our analysis, the validity of cosmic distance duality relation is assumed. We find a mildly decreasing trend for the gas depletion factor as a function of redshift at about 2.7$σ$. This is the first result in literature which does not find a constant gas depletion factor as a function of redshift using gas mass fraction measurements at $r_{2500}$.

astro-ph.CO↗

arXiv2022

Dark matter from torsion in Friedmann cosmology

A cosmological model in an Einstein-Cartan framework endowed with torsion is studied. For a torsion function assumed to be proportional to Hubble expansion function, namely $ϕ=-αH$, the contribution of torsion function as a dark matter component is studied in two different approaches. In the first one, the total matter energy density is altered by torsion coupling $α$, giving rise to an effective dark matter and cosmological constant terms that reproduce quite well the flat cosmic concordance model. In the second approach, starting with just standard baryonic matter plus a cosmological constant term, it is obtained that the coupling of torsion with baryons and cosmological constant term naturally gives rise to a dark matter contribution, together a modified cosmological term. In this model the dark matter sector can be interpreted as an effective coupling of the torsion function with the ordinary baryonic matter and cosmological constant. Finally, it is shown that both models are totally compatible with recent cosmological data from Supernovae and Hubble parameter measurements.

gr-qc↗

arXiv2022

A non-parametric test of variability of Type Ia supernovae luminosity and CDDR

The first observational evidence for cosmic acceleration appeared from Type Ia supernovae (SNe Type Ia) Hubble diagram from two different groups. However, the empirical treatment of SNe Type Ia and their ability to show cosmic acceleration have been the subject of some debate in the literature. In this work we probe the assumption of redshift-independent absolute magnitude $(M_{\mathrm{B}})$ of SNe along with its correlation with spatial curvature ($Ω_{k0}$) and cosmic distance duality relation (CDDR) parameter ($η(z)$). This work is divided into two parts. Firstly, we check the validity of CDDR which relates the luminosity distance ($d_L$) and angular diameter distance ($d_A$) via redshift. We use the Pantheon SNe Ia dataset combined with the $H(z)$ measurements derived from the cosmic chronometers. Further, four different redshift-dependent parametrizations of the distance duality parameter $(η(z))$ are used. The CDDR is fairly consistent for almost every parametrization within a $2σ$ confidence level in both flat and a non-flat universe. In the second part, we assume the validity of CDDR and emphasize on the variability of $M_{\mathrm{B}}$ and its correlation with $Ω_{k0}$. We choose four different redshift-dependent parametrizations of $M_{\mathrm{B}}$. The results indicate no evolution of $M_{\mathrm{B}}$ within $2σ$ confidence level. For all parametrizations, the best fit value of $Ω_{k0}$ indicates a flat universe at $2σ$ confidence level. However a mild inclination towards a non flat universe is also observed. We have also examined the dependence of the results on the choice of different priors for $H_0$.

astro-ph.CO↗