Cosmological singularities in interacting dark energy models with an $\omega(q)$ parametrization

TL;DR

This paper classifies future cosmological singularities in interacting dark energy models using a parametrization based on the deceleration parameter, reconstructed from observational data, and analyzes their stability and potential astrophysical implications.

Contribution

It introduces a novel parametrization of dark energy with interaction terms, reconstructed from $H(z)$ data, and explores the resulting singularities and stability properties of the models.

Findings

Non-interacting model can evolve into a stable de Sitter universe.

Interacting model with $Q=3Hb ho_{dm}$ has three stable critical points.

Finite-time future singularities of Type I, III, or $ extomega$-singularity can occur.

Abstract

Future singularities arising in a family of models for the expanding Universe, characterized by sharing a convenient parametrization of the energy budget in terms of the deceleration parameter, are classified. Finite-time future singularities are known to appear in many cosmological scenarios, in particular, in the presence of viscosity or non-gravitational interactions, the last being known to be able to suppress or just change in some cases the type of the cosmological singularity. Here, a family of models with a parametrization of the energy budget in terms of the deceleration parameter are studied in the light of Gaussian processes using reconstructed data from $40$-value $H(z)$ datasets. Eventually, the form of the possible non-gravitational interaction between dark energy and dark matter is constructed from these smoothed $H(z)$ data. Using phase space analysis, it is shown that a non-interacting model with dark energy $\omega_\mathrm{de} = \omega_{0} + \omega_{1}q$ ($q$ being the deceleration parameter) may evolve, after starting from a matter dominated unstable state, into a de Sitter Universe (the solution being in fact a stable node). Moreover, for a model with interaction term $Q = 3 H b \rho_\mathrm{dm}$ ($b$ is a parameter and $H$ the Hubble constant) three stable critical points are obtained, what may have important astrophysical implications. In addition, part of the paper is devoted to a general discussion of the finite-time future singularities obtained from direct numerical integration of the field equations, since they appear in many cosmological scenarios and could be useful for future extended studies of the models here introduced. Numerical solutions for the new models, produce finite-time future singularities of Type I or Type III, or an $\omega$-singularity, provided general relativity describes the background dynamics.