Parametric resonance in abelian and non-abelian gauge fields via space-time oscillations

TL;DR

This paper investigates how space-time oscillations can induce parametric resonance in abelian and non-abelian gauge fields, leading to significant fluctuations and potential implications for early universe phenomena.

Contribution

It demonstrates the presence of parametric resonance in both abelian and non-abelian gauge fields due to space-time oscillations, including non-linear effects via numerical simulations.

Findings

Resonant modes cause large fluctuations in gauge fields.

Energy density increases with coupling strength at late times.

Gravitational waves may excite gauge fields and enhance CP-violation.

Abstract

We study the evolution of abelian $U(1)$ electromagnetic as well as non-abelian $SU(2)$ gauge fields, in the presence of space-time oscillations. Analysis of the time evolution of abelian gauge fields shows the presence of parametric resonance in spatial modes. A similar analysis in the case of non-abelian gauge fields, in the linear approximation, shows the presence of the same resonant spatial modes. The resonant modes induce large fluctuations in physical observables including those that break the $CP-$symmetry. We also carry out time evolution of small random fluctuations of the gauge fields, using numerical simulations in $2+1$ and $3+1$ dimensions. These simulations help to study non-linear effects in the case of non-abelian gauge theories. Our results show that there is an increase in energy density with the coupling, at late times. These results suggest that gravitational waves may excite non-abelian gauge fields more efficiently than electromagnetic fields. Also, gravitational waves in the early Universe and from the merger of neutron stars, black holes etc. may enhance $CP-$violation and generate an imbalance in chiral charge distributions, magnetic fields etc.