Bianchi type I universes with dilaton and magnetic fields

TL;DR

This paper analyzes the evolution of Bianchi type I universes influenced by dilaton and magnetic fields, providing exact solutions and showing persistent anisotropy over time.

Contribution

It presents exact parametric solutions for Einstein-Maxwell dilaton equations in Bianchi type I spacetime and classifies solutions based on parameter values.

Findings

Magnetic-dilaton Bianchi I universes do not isotropize over time.

Three distinct classes of solutions are identified.

Initial anisotropy persists throughout the evolution.

Abstract

We consider the dynamics of a Bianchi type I spacetime in the presence of dilaton and magnetic fields. The general solution of the Einstein-Maxwell dilaton field equations can be obtained in an exact parametric form. Depending on the numerical values of the parameters of the model there are three distinct classes of solutions. The time evolution of the mean anisotropy, shear and deceleration parameter is considered in detail and it is shown that a magnetic-dilaton anisotropic Bianchi type I geometry does not isotropize, the initial anisotropy being present in the universe for all times.