Energymomentum tensor and helicity for gauge fields coupled to a pseudoscalar inflaton
Abstract
We study the energymomentum tensor and helicity of gauge fields coupled through g ϕ F F ∼/4 to a pseudoscalar field ϕ driving inflation. Under the assumption of a constant time derivative of the background inflaton, we compute analytically divergent and finite terms of the energy density and helicity of gauge fields for any value of the coupling g . We introduce a suitable adiabatic expansion for mode functions of physical states of the gauge fields which correctly reproduces ultraviolet divergences in average quantities and identifies corresponding counterterms. Our calculations shed light on the accuracy and the range of validity of approximated analytic estimates of the energy density and helicity terms previously existed in the literature in the strongly coupled regime only, i.e., for g ϕ ˙ /(2 H )≫1 . We discuss the implications of our analytic calculations for the backreaction of quantum fluctuations onto the inflaton evolution.
 Publication:

Physical Review D
 Pub Date:
 December 2019
 DOI:
 10.1103/PhysRevD.100.123542
 arXiv:
 arXiv:1910.13448
 Bibcode:
 2019PhRvD.100l3542B
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Theory
 EPrint:
 18 pages, 9 figures. Corrected some typos and removed Appendix B. The results are unchanged