Anisotropic solid dark energy

TL;DR

This paper investigates a solid scalar field model as a source of anisotropic dark energy, showing it can produce accelerated expansion with observable anisotropy or isotropize depending on parameters, and can mimic a cosmological constant.

Contribution

It introduces a solid scalar field model for anisotropic dark energy and analyzes its dynamical behavior, including attractors and isotropization conditions.

Findings

Anisotropic accelerated solutions can be attractors.

The universe can isotropize depending on parameters.

The model can mimic a cosmological constant.

Abstract

In this paper, we study a triad of inhomogeneous scalar fields, known as "solid", as a source of homogeneous but anisotropic dark energy. By using a dynamical system approach, we find that anisotropic accelerated solutions can be realized as attractor points for suitable choices of the parameters of the model. We complement the dynamical analysis with a numerical solution whose initial conditions are set in the deep radiation epoch. The model can give an account of a non-negligible spatial shear within the observational bounds nowadays, even when the later is set to zero at early times. However, we find that there is a particular region in the parameter space of the model in which the Universe isotropizes. The anisotropic attractors, the particular isotropic region, and a nearly constant equation of state of dark energy very close to $- 1$ are key features of this scenario. Following a similar approach, we also analyzed the full isotropic version of the model. We find that the solid can be characterized by a constant equation of state and thus being able to simulate the behavior of a cosmological constant.