arXiv subjects

Ana A. Avilez-López

Publications and source records attributed to Ana A. Avilez-López.

4 recordsLinked to original sources

arXiv2025

Forecasts for lifetime and fraction of Decaying Dark Matter based on redshift distortions from Euclid and BOSS

In this work we forecast constraints on models of decaying dark matter (DCDM) by using redshift-space-distortion (RSD) measurements implemented in a Fisher information matrix. In particular, we focus on the fraction of unstable dark matter, $α_{\mathrm{dcdm}}$ respect to the ordinary CDM component, and the decay rate, $Γ_{\mathrm{dcdm}}$ as the key parameters of the model. Fiducial values are derived from a MontePython MCMC analysis. The derivatives of the growth-related observable, $fσ_8(z)$ with respect to the parameters are numerically around the fiducial model. For the Fisher analysis, we employ mock data designed for upcoming surveys, particularly Euclid and BOSS, where RSD measurements yield constraints on $fσ_8.$ Our results show that when both stable and unstable components are allowed, constrains on the DCDM lifetime remain weak, with $τ_{\mathrm{dcdm}}>1.18$ Gyr. In the limiting case of fully unstable dark matter ($α_{\mathrm{dcdm}}=1$), the uncertainty improves to $τ_{\mathrm{dcdm}}>235.89$ Gyr. Our findings highlight the potential of RSD probes in testing and complementing decaying dark matter scenarios.

astro-ph.CO↗

arXiv2025

Thermodynamics of an universe with Decaying Cold Dark Matter

In this work we focus on the thermodynamics consistency of a new set of solutions emerging from a cosmology in which dark matter is able to decay into relativistic particles within the dark sector. It is important to stress that the lifetime of dark matter is larger than the age of the universe in order to be consistent with observations. Given that the corresponding decay rate is small, this one can be used as a perturbative parameter and it is possible to construct analytic solutions from a perturbative analysis for the densities of the species and the scale factor. The decay of dark matter is an irreversible process since it occurs out of chemical equilibrium and therefore the entropy per comoving volume increases considerably, as a consequence the temperature does not scale as $a^{-1}$ in contrast to an adiabatic expansion. We take into account two scenarios: a) The case in which both species making up the fluid end up in thermal equilibrium and therefore their temperature is the same. b) A second instance in which the species do not reach thermal equilibrium and therefore they have different temperatures. We verify that the second law of thermodynamics is satisfied in any case.

gr-qc↗

arXiv2025

Exploring the cosmological degeneracy between decaying dark matter model and viscous $Λ$CDM

In the context of a homogeneous and isotropic universe, we consider the degeneracy condition at the background level between two scenarios in which processes out of equilibrium are possible; this consideration allows us to deviate from the perfect fluid description, and in this case bulk viscosity represents a viable candidate to describe entirely such effects. The cosmological model describing an unstable dark matter sector is mapped into a slight modification of the $Λ$CDM model characterized by a viscous dark matter sector; under this consideration our description does not depend on a specific formulation of viscous effects and these can be fully reconstructed and characterized by the parameter that determines the decay ratio of dark matter. However, in this new scenario the cosmic expansion is influenced by the viscous pressure and the dark energy sector given by the cosmological constant is translated into a dynamical one. As a consequence of our formulation, the test against observations of the model indicates consistency with quintessence dark energy, but the crossing of the phantom divide can be accessible.

gr-qc↗

arXiv2022

Qualitative analysis for viscous cosmologies in a non linear regime of the Israel-Stewart formalism

We explore the dynamical properties of a cosmological model that includes viscous effects in the dark matter sector of the fluid equations in a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. The bulk viscous effects are described by a non linear extension of the full Israel-Stewart model. We allow the interchange of energy in the dark sector by means of the interaction term, namely $Q$. We establish the dynamical system corresponding to Friedmann and fluid set of equations associated to the model and study the linear stability of its critical points. From the dynamical system, we show the appearance of a critical point characterizing a de Sitter universe within the non interacting and interacting dark sector. We focus our study to analyse the stability of this fixed point in a large region of parameter space and derive linearized solutions around it. These approximate and analytical solutions are potentially able to describe the expansion of the universe since they are close to a de Sitter stationary solution. Within this regime with $Q \neq 0$, we realize the existence of regions in the space of parameters where this critical point is stable and describes the behavior of dark energy as quintessence, cosmological constant and phantom like fluids. We perform a comparison between numerical and linearized solutions nearby the critical points within the full non linear regimes and also contrast them against $Λ$CDM model. We find that fully non linear regime is favored by observations and closer to the concordance model due to the non-zero value of the parameter $j$, which controls the non linear effects. In fact, at low redshift values, the expansion rate associated to the full non linear regime is practically indistinguishable from $Λ$CDM. The deceleration parameter obtained in this regime exhibits a transition from decelerated to accelerated cosmic expansion.

gr-qc↗