Cosmological Co-evolution of Yang-Mills Fields and Perfect Fluids

TL;DR

This paper investigates the coupled evolution of Yang-Mills fields and perfect fluids in anisotropic Bianchi type I universes, revealing chaotic oscillations and weaker constraints from nucleosynthesis compared to magnetic fields.

Contribution

It provides a numerical and analytical study of Yang-Mills field dynamics in cosmology, highlighting differences from magnetic field evolution and constraints.

Findings

Yang-Mills fields exhibit small amplitude chaotic oscillations.

Yang-Mills universes face weaker primordial nucleosynthesis constraints.

Omega_YM is less than 0.105 times Omega_rad.

Abstract

We study the co-evolution of Yang-Mills fields and perfect fluids in Bianchi type I universes. We investigate numerically the evolution of the universe and the Yang-Mills fields during the radiation and dust eras of a universe that is almost isotropic. The Yang-Mills field undergoes small amplitude chaotic oscillations, which are also displayed by the expansion scale factors of the universe. The results of the numerical simulations are interpreted analytically and compared with past studies of the cosmological evolution of magnetic fields in radiation and dust universes. We find that, whereas magnetic universes are strongly constrained by the microwave background anisotropy, Yang-Mills universes are principally constrained by primordial nucleosynthesis and the bound is comparatively weak, and Omega_YM < 0.105 Omega_rad.