arXiv subjects

A. A. Escobal

Publications and source records attributed to A. A. Escobal.

11 recordsLinked to original sources

arXiv2026

Interacting Dark Sector field theory with phantom crossing

Recent results from the Dark Energy Spectroscopic Instrument (DESI) provide evidence for a dynamical dark-energy component, whose equation of state appears to have recently crossed the phantom divide. In this Letter, we present an interacting dark-energy model, grounded in field theory, that naturally accommodates such a double crossing. In our framework, fermionic dark matter is coupled via a Yukawa interaction to a tachyonic scalar field governed by Born-Infeld dynamics. The phantom crossing arises at the level of the effective dark-energy equation of state, while the underlying scalar-field dynamics remains nonphantom and well bounded. We confront our model with data including BAO from the DESI (DR2) survey, CMB distance priors from Planck 2018, and the latest Type Ia supernovae compilations, obtaining robust constraints across the different data combinations and reconstructing a recent double crossing of the phantom divide. Furthermore, under naturalness assumptions, the model expects an ultralight fermionic dark matter mass of order $1.9\times10^{-3}\,\mathrm{eV}$, suggesting a possible connection with new light particles in the dark sector and motivating future tests with cosmological perturbations.

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arXiv2026

Linear Growth of Matter Perturbations Probed by Redshift-Space Distortions in Interacting $Λ(t)$CDM Cosmologies

In the context of a spatially flat $Λ(t)$CDM cosmology, we investigate interacting dark energy (IDE) scenarios characterized by phenomenological interaction terms proportional to the Hubble expansion rate and the dark energy density. Our analysis is performed at both the background and linear perturbation levels, with particular emphasis on the evolution of dark matter density fluctuations. Cosmological constraints are derived from a joint analysis of CMB distance priors, Baryon Acoustic Oscillations (BAO), Type Ia supernovae (SNe Ia) from Pantheon+, Redshift-Space Distortions (RSD), and $H(z)$ data from Cosmic Chronometers (CC). Using the linear growth of matter perturbations, we estimate the clustering parameter $S_8$ within IDE extensions of the flat $Λ(t)$CDM framework. At the perturbative level, we consider interaction terms of the form $Q_{\text{I}}=\varepsilon a H\barρ_{Λ(t)}$ (Model I) and $Q_{\text{II}}=\varepsilon H\barρ_{Λ(t)}$ (Model II). From the combined dataset, we obtain the constraints $S_8 = 0.870 \pm 0.026$ for Model I and $S_8 = 0.872 \pm 0.026$ for Model II. Finally, we discuss the implications for the coupling parameter $\varepsilon$, taking into account the semi-analytical approximations and observational data employed in this study.

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arXiv2026

A microphysically inspired approach to dark matter-dark energy interactions: first bounds on dark-sector scattering cross sections

The observational tension regarding the value of the Hubble constant ($H_0$) has motivated the exploration of alternative cosmological scenarios, including Interacting Dark Energy models. However, the majority of IDE models studied in the literature rely on phenomenological interaction terms proportional to the Hubble parameter (e.g., $Q\propto H\rho$), which lack a clear microphysical justification and often suffer from large-scale instabilities. In this work, we propose and investigate a "bottom-up" IDE model where the interaction is formulated directly from particle physics collision processes, taking the form $Q\propto\rho^2$. This interaction represents a reversible annihilation/creation process between Dark Matter and Dark Energy, motivated by the Boltzmann equation. We test this model against a combination of background cosmological data, Pantheon Plus, Cosmic Chronometers, DESI DR2, and CMB distance priors from Planck18. We find that the model is consistent with the data, yielding a Hubble constant of $H_0=67.71\pm0.65$ km s$^{-1}$ Mpc$^{-1}$ for the combined analysis. The dimensionless interaction rate coefficients are constrained to be small, with upper limits of $A < 7.586\times10^{-25}$ (for Dark Matter self annihilation) and $B < 0.048$ (for Dark Energy self annihilation) at 95\% confidence level. Since the interaction model is parameterized by the expansion rate, these bounds on $H_0$, $A$, and $B$ directly translate into a strict limit on the thermally-averaged annihilation cross-section per unit of mass. The constraints on the coupling $A$ imply that, if such a collisional interaction exists, the effective dark-matter annihilation cross section per unit mass is highly suppressed relative to the cosmological expansion rate. In contrast, the corresponding dark-energy contribution, governed by $B$, is only constrained at the level of a few percent in dimensionless units.

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arXiv2025

Can decaying vacuum solve the H_0 Tension?

In the present work we analyze two different models of interaction between dark energy and dark matter, also known as vacuum decay models or $Λ(t)$CDM models. In both models, when the $H_0$ parameter is constrained by the Planck distance priors, its value is compatible with a higher value of $H_0$, in agreement with SH0ES data, while simultaneously reducing the values of $Ω_m$ and $Ω_b$. In both models, we find $H_0=73.1\pm0.86$ at 68\% c.l. by combining Planck+SH0ES data. We also find the decay parameter to be $\varepsilon=0.0197^{+0.0032}_{-0.0027}$ for one model and $\varepsilon=0.0203\pm0.0034$ for the other one. From these analyses, a noninteracting model is excluded at least at $6σ$ c.l.! This shows that these types of models are promising in solving or at least alleviating the $H_0$ tension problem. Our analysis also shows a preference for the decay of vacuum into dark matter, in agreement to thermodynamic analyses.

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arXiv2023

Can the Universe decelerate in the future?

The possibility of an expanding decelerating Universe in the distant future is investigated in the context of a quintessence scalar field cosmology. Such a conceivable evolution is tested against SNe Ia and $H(z)$ cosmic chronometers data, and also through a model independent method based on Gaussian Processes. The scalar field model is an extension of the exponential Ratra-Peebles (RP) quintessential cosmology whose potential now depends on a pair of parameters ($α, λ)$ and predicts a decelerated expansion in the future. Different from RP approach the $α$ parameter allows for a decelerating cosmology in the future thereby frustrating the inevitable evolution for a de Sitter Cosmology as predicted by the cosmic concordance model ($Λ$CDM). The statistical model analysis is updated with the most recent SNe Ia and $H(z)$ data thereby obtaining $H_0 = 68.6\pm3.7$ km/s/Mpc, $Ω_{\Phi0} = 0.735^{+0.083}_{-0.069} $, $α< 6.56$ and $λ< 0.879 $ (at $2σ$ c.l.). It is also found that the extended RP model allows for a future deceleration both for $H(z)$ and SNe Ia data. In the (model-independent) Gaussian Processes analysis, however, future deceleration is allowed only in the case of $H(z)$ data.

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arXiv2023

A Method for Obtaining Cosmological Models Consistency Relations and Gaussian Processes Testing

In the present work, we apply consistency relation tests to several cosmological models, including the flat and non-flat $Λ$CDM models, as well as the flat XCDM model. The analysis uses a non-parametric Gaussian Processes method to reconstruct various cosmological quantities of interest, such as the Hubble parameter $H(z)$ and its derivatives from $H(z)$ data, as well as the comoving distance and its derivatives from SNe Ia data. We construct consistency relations from these quantities which should be valid only in the context of each model and test them with the current data. We were able to find a general method of constructing such consistency relations in the context of $H(z)$ reconstruction. In the case of comoving distance reconstruction, there were not a general method of constructing such relations and this work had to write an specific consistency relation for each model. From $H(z)$ data, we have analyzed consistency relations for all the three above mentioned models, while for SNe Ia data we have analyzed consistency relations only for flat and non-flat $Λ$CDM models. Concerning the flat $Λ$CDM model, some inconsistency was found, at more than $2σ$ c.l., with the $H(z)$ data in the interval $1.8\lesssim z\lesssim2.4$, while the other models were all consistent at this c.l. Concerning the SNe Ia data, the flat $Λ$CDM model was consistent in the $0<z<2.5$ interval, at $1σ$ c.l., while the nonflat $Λ$CDM model was consistent in the same interval, at 2$σ$ c.l.

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arXiv2022

From Hubble to Snap Parameters: A Gaussian Process Reconstruction

By using recent $H(z)$ and SNe Ia data, we reconstruct the evolution of kinematic parameters $H(z)$, $q(z)$, jerk and snap, using a model-independent, non-parametric method, namely, the Gaussian Processes. Throughout the present analysis, we have allowed for a spatial curvature prior, based on Planck 18 constraints. In the case of SNe Ia, we modify a python package (GaPP) in order to obtain the reconstruction of the fourth derivative of a function, thereby allowing us to obtain the snap from comoving distances. Furthermore, using a method of importance sampling, we combine $H(z)$ and SNe Ia reconstructions in order to find joint constraints for the kinematic parameters. We find for the current values of the parameters: $H_0 =67.2 \pm 6.2$ km/s/Mpc, $q_0 = -0.54^{+0.06}_{-0.05}$, $j_0=0.94^{+0.20}_{-0.18}$, $s_0=-0.62^{+0.26}_{-0.25}$ at 1$\sigma$ c.l. We find that these reconstructions are compatible with the predictions from flat $\Lambda$CDM model, at least for 2$\sigma$ confidence intervals.

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arXiv2022

Gaussian Processes Reconstruction of the Dark Energy Potential

Scalar Fields (SF) have emerged as natural candidates for dark energy as quintessential or phantom fields, as they are the main ingredient of inflation theories. Instead of assuming some form for the scalar field potential, however, this work reconstructs the SF potential directly from observational data, namely, \textbf{Hubble and SNe Ia data}. We show that two popular forms for the SF potentials, namely, the power-law and the quadratic free-field, are compatible with the reconstructions thus obtained, at least for some choices of the priors of the matter density and curvature parameters and for some redshift intervals.

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arXiv2022

Can dark matter-dark energy interaction alleviate the Cosmic Coincidence Problem?

In this paper we study a model of interacting dark energy - dark matter where the ratio between these components is not constant, changing from early to late times in such a way that the model can solve or alleviate the cosmic coincidence problem (CP). The interaction arises from an assumed relation of the form $ρ_x \propto ρ_d^α$, where $ρ_x$ and $ρ_d$ are the energy densities of dark energy and dark matter components, respectively, and $α$ is a free parameter. For a dark energy equation of state parameter $w=-1$ we found that, if $α=0$, the standard $Λ$CDM model is recovered, where the coincidence problem is unsolved. For $0<α<1$, the CP would be alleviated and for $α\sim 1$, the CP would be solved. The dark energy component is analyzed with both $w=-1$ and $w \neq -1$. Using Supernovae type Ia and Hubble parameter data constraints, in the case $w=-1$ we find $α=0.109^{+0.062}_{-0.072}$ at 68% C.L., and the CP is alleviated. For $w\neq -1$, a degeneracy arises on the $w$ - $α$ plane. In order to break such degeneracy we add cosmic microwave background distance priors and baryonic acoustic oscillations data to the constraints, yielding $α=-0.075\pm 0.046$ at 68% C.L.. In this case we find that the CP is not alleviated even for 2$σ$ interval for $α$. Furthermore, this last model is discarded against flat $Λ$CDM according to BIC analysis.

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arXiv2020

Cosmological Constraints on Scalar Field Dark Matter

This paper aims to put constraints on the parameters of the Scalar Field Dark Matter (SFDM) model, when dark matter is described by a free real scalar field filling the whole Universe, plus a cosmological constant term. By using a compilation of 51 $H(z)$ data and 1048 Supernovae data from Panteon, a lower limit for the mass of the scalar field was obtained, $m \geq 5.1\times 10^{-34} $eV and $H_0=69.5^{+2.0}_{-2.1}\text{ km s}^{-1}\text{Mpc}^{-1}$. Also, the present dark matter density parameter was obtained as $Ω_ϕ= 0.230^{+0.033}_{-0.031}$ at $2σ$ confidence level. The results are in good agreement to standard model of cosmology, showing that SFDM model is viable in describing the dark matter content of the universe.

astro-ph.CO↗

arXiv2019

Gaussian Process Estimation of Transition Redshift

This paper aims to put constraints on the transition redshift $z_t$, which determines the onset of cosmic acceleration, in cosmological-model independent frameworks. In order to do that, we use the non-parametric Gaussian Process method with $H(z)$ and SNe Ia data. The deceleration parameter reconstruction from $H(z)$ data yields $z_t=0.59^{+0.12}_{-0.11}$. The reconstruction from SNe Ia data assumes spatial flatness and yields $z_t=0.683^{+0.11}_{-0.082}$. These results were found with a Gaussian kernel and we show that they are consistent with two other kernel choices.

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