Inflation with Multi-Vector-Hair: The Fate of Anisotropy

TL;DR

This paper investigates how multiple vector fields influence inflation, revealing conditions under which anisotropy persists or diminishes, and demonstrating the universe's tendency towards isotropy or anisotropic attractors depending on coupling types.

Contribution

It provides a comprehensive analysis of multi-vector inflation models, highlighting the conditions for anisotropic hair and the universe's evolution towards isotropy or anisotropic attractors.

Findings

No-hair conjecture does not hold with non-trivial couplings.

The universe approaches isotropy with uniform couplings.

Anisotropic inflation attractors can occur with general couplings.

Abstract

We study inflation with multiple vector fields. In the presence of non-trivial couplings between the inflaton and the vector fields, it turns out that no-hair conjecture does not hold and vector-hair appears. In the case of uniform couplings, nevertheless, we find that the universe approaches an isotropic final state after transient anisotropic inflationary phases. For general couplings, we numerically show attractors are anisotropic inflation. Even in these cases, it turns out that the inflation always tends to minimize the anisotropy in the expansion of the universe.