Energy-momentum tensor and helicity for gauge fields coupled to a pseudo-scalar inflaton

Journal
Date Issued
2019
Author(s)
•
BRAGLIA, MATTEO
•
•
Marozzi, Giovanni
•
Starobinsky, Alexei A.
DOI
Abstract
We study the energy-momentum tensor and helicity of gauge fields coupled through $g \phi F \tilde{F}/4$ to a pseudo-scalar field $\phi$ driving inflation. Under the assumption of a constant time derivative of the background inflaton, we compute analitically 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 identify 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 $g \dot \phi/(2H) \gg 1$. We discuss the implications of our analytic calculations for the backreaction of quantum fluctuations onto the inflaton evolution.
Volume
100
Issue
12
Uri
Url
Issn Identifier
2470-0010
Ads BibCode
2019PhRvD.100l3542B
Rights
open.access
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