Evolution of superhorizon perturbations in early Universe with anisotropic solid remnant

TL;DR

This paper investigates how a small anisotropic solid remnant in the early Universe influences superhorizon perturbations, revealing growth in scalar and vector modes and potential observational implications.

Contribution

It introduces a model with anisotropic solid remnants affecting early Universe expansion and perturbation evolution, extending solid inflation theories.

Findings

Scalar and vector perturbations grow on superhorizon scales.

Tensor perturbations remain unchanged from standard radiation-dominated universe.

In certain limits, vector perturbations decrease with a different power law, improving data agreement.

Abstract

We study effects of presence of a small amount of so-called anisotropic solid remnant in the early post-inflationary Universe dominated by radiation. This model is inspired by solid inflation and its generalizations with matter described through a triplet of fields. In our model, the internal full global Euclidean symmetry of this triplet is broken, which leads to an anisotropic expansion of the Universe. Superhorizon scalar and vector perturbations grow, while behavior of tensor perturbations remains the same as in the standard case with Universe filled with only radiation. We also find a very interesting case within the limit of a very small amount of the anisotropic solid remnant and the longest possible duration of its presence, where size of vector perturbations decreases with a different power of scale factor as in the standard scenario. The obtained results improve agreement between the observational data and the theoretical predictions of solid inflation in a case with suppressed non-linear effects.