Thawing models in the presence of a generalized Chaplygin gas

TL;DR

This paper explores cosmological models combining scalar fields and generalized Chaplygin gas, deriving exact solutions and analyzing late-time behaviors, revealing that Chaplygin gas influences the scalar field dynamics and potential attractors.

Contribution

It introduces exact solutions for flat cosmologies with scalar fields and generalized Chaplygin gas, and applies dynamical systems to analyze late-time attractors and their dependence on model parameters.

Findings

Scalar field and Chaplygin gas can coexist with specific late-time attractors.

Standard scalar-field-dominated solutions are not late-time attractors with Chaplygin gas.

Late-time attractors include de Sitter and generalized Chaplygin solutions depending on parameters.

Abstract

In this paper we consider a cosmological model whose main components are a scalar field and a generalized Chaplygin gas. We obtain an exact solution for a flat arbitrary potential. This solution have the right dust limit when the Chaplygin parameter $A\rightarrow 0$. We use the dynamical systems approach in order to describe the cosmological evolution of the mixture for an exponential self-interacting scalar field potential. We study the scalar field with an arbitrary self-interacting potential using the "Method of $f$-devisers." Our results are illustrated for the special case of a coshlike potential. We find that usual scalar-field-dominated and scaling solutions cannot be late-time attractors in the presence of the Chaplygin gas (with $\alpha>0$). We recover the standard results at the dust limit ($A\rightarrow 0$). In particular, for the exponential potential, the late-time attractor is a pure generalized Chaplygin solution mimicking an effective cosmological constant. In the case of arbitrary potentials, the late-time attractors are de Sitter solutions in the form of a cosmological constant, a pure generalized Chaplygin solution or a continuum of solutions, when the scalar field and the Chaplygin gas densities are of the same orders of magnitude. The different situations depend on the parameter choices.