Dynamics of super-horizon photons during inflation with vacuum polarization

TL;DR

This paper investigates the late-time behavior of super-horizon photons during inflation, revealing complex dynamics influenced by vacuum polarization effects modeled via scalar electrodynamics.

Contribution

It provides a detailed analysis of photon evolution in a de Sitter universe, showing the electric field behaves like an Airy oscillator and the magnetic field stabilizes to a nonzero value.

Findings

Electric field approaches an Airy oscillator dynamics.

Magnetic field asymptotically stabilizes to a nonzero constant.

Photon dynamics differ from those of a massive Proca photon.

Abstract

We study asymptotic dynamics of photons propagating in the polarized vacuum of a locally de Sitter Universe. The origin of the vacuum polarization is fluctuations of a massless, minimally coupled, scalar, which we model by the one-loop vacuum polarization tensor of scalar electrodynamics. We show that late time dynamics of the electric field on superhorizon scales approaches that of an Airy oscillator. The magentic field amplitude, on the other hand, asymptotically approaches a nonvanishing constant (plus an exponentially small oscillatory component), which is suppressed with respect to the initial (vacuum) amplitude. This implies that the asymptotic photon dynamics is more intricate than that of a massive photon obeying the local Proca equation.