Vector fields in cosmology

TL;DR

This paper explores how vector fields, both abelian and non-abelian, can influence cosmological dynamics, including inflation, through various theoretical mechanisms and models.

Contribution

It introduces models of vector fields in cosmology arising from geometrical origins and non-linear Yang-Mills theories that can produce inflationary behavior.

Findings

Geometrical vector fields can lead to complex scalar-tensor dynamics.

Non-linear Yang-Mills models can support inflation with exponential scale factor growth.

Effective electric and magnetic components behave like slowly varying scalars during inflation.

Abstract

Vector fields can arise in the cosmological context in different ways, and we discuss both abelian and nonabelian sector. In the abelian sector vector fields of the geometrical origin (from dimensional reduction and Einstein-Eddington modification of gravity) can provide a very non-trivial dynamics, which can be expressed in terms of the effective dilaton-scalar gravity with the specific potential. In the non-abelian sector we investigate the Yang-Mills SU(2) theory which admits isotropic and homogeneous configuration. Provided the non-linear dependence of the lagrangian on the invariant F*F(dual), one can obtain the inflationary regime with the exponential growth of the scale factor. The effective amplitudes of the 'electric' and 'magnetic' components behave like slowly varying scalars at this regime, what allows the consideration of some realistic models with non-linear terms in the Yang-Mills lagrangian.