Schwinger Effect in Inflaton-Driven Electric Field

TL;DR

This paper studies the Schwinger effect during inflation, showing how pair production in an inflaton-driven electric field leads to a decreasing electric field, supporting the no-hair theorem.

Contribution

It provides a semiclassical analysis of pair production and backreaction in an inflaton-coupled electric field during inflation, confirming the no-hair theorem.

Findings

Electric field decreases with cosmic expansion.

Dilatonic coupling ensures valid semiclassical approximation.

No anisotropic hair persists during inflation.

Abstract

In a four dimensional inflation theory, a persistent electric field can be established by making the inflaton coupled to the gauge field like a dilaton. We investigate the pair production of scalar particles in the inflaton-driven electric field. In particular, we evaluate the induced current due to the pair production. The presence of the dilatonic coupling ensures the validity of the WKB approximation at the past and the future infinities, without tuning constant parameters. Thus, the semiclassical description is applicable in evaluating the induced current. Solving the field equations with the induced current, we evaluate the first-order backreaction to the electric field. It turns out that the electric field decreases with the cosmic expansion. The result indicates that the no-anisotropic hair theorem for inflation holds true regardless of whether the dilatonic coupling is present or not.