Parametric resonance in Abelian and non-Abelian gauge fields via spacetime oscillations

Abstract

We study the evolution of Abelian U(1) electromagnetic as well as non-Abelian SU(2) gauge fields, in the presence of spacetime 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 nonlinear 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. Published by the American Physical Society 2024