Gauge Field Theory Vacuum and Cosmological Inflation

TL;DR

This paper reviews how quantum vacuum fluctuations of gauge fields, especially Yang-Mills fields, can influence cosmological inflation and late-time acceleration, offering an alternative mechanism for universe expansion and gravitational wave generation.

Contribution

It derives the quantum energy-momentum tensor for gauge fields and explores their impact on cosmology, proposing new solutions for inflation and acceleration driven by vacuum polarization effects.

Findings

Gauge field vacuum polarization can induce inflationary expansion.

Solutions suggest a mechanism for late-time cosmic acceleration.

Primordial gravitational waves can be amplified by these effects.

Abstract

The deep interrelation between elementary particle physics and cosmology manifests itself when one considers the contribution of quantum fluctuations of vacuum fields to the dark energy and the effective cosmological constant. The contribution of zero-point energy exceeds by many orders of magnitude the observational cosmological upper bound on the energy density of the universe. Therefore it seems natural to expect that vacuum fluctuations of the fundamental fields would influence the cosmological evolution in any way. Our aim in this review article is to describe a recent investigation of the influence of the Yang-Mills vacuum polarisation and of the chromomagnetic condensation on the evolution of Friedmann cosmology, on inflation and on primordial gravitational waves. We derive the quantum energy-momentum tensor and the corresponding quantum equation of state for gauge field theory using the effective Lagrangian approach. The energy-momentum tensor has a term proportional to the space-time metric and provides a finite non-diverging contribution to the effective cosmological constant. This allows to investigate the influence of the gauge field theory vacuum polarisation on the evolution of Friedmann cosmology, inflation and primordial gravitational waves. The Type I-IV solutions of the Friedmann equations induced by the gauge field theory vacuum polarisation provide an alternative inflationary mechanism and a possibility for late-time acceleration. The Type II solution of the Friedmann equations generates the initial exponential expansion of the universe of finite duration and the Type IV solution demonstrates late-time acceleration. The solutions fulfil the necessary conditions for the amplification of primordial gravitational waves.