Smooth magnetogenesis

TL;DR

This paper investigates the impact of smoothing the coupling function in inflationary magnetogenesis models, showing that the main predictions remain valid while addressing issues caused by nonanalytical jumps.

Contribution

It introduces smooth analytical forms of the coupling function in the Ratra model, demonstrating that the main magnetogenesis predictions are robust against such modifications.

Findings

Main predictions remain valid with smooth coupling functions.

Nonanalytical jumps cause spurious ultraviolet photon spectra.

Smooth functions eliminate unphysical power-law decay in photon spectrum.

Abstract

In the Ratra scenario of inflationary magnetogenesis, the kinematic coupling between the photon and the inflaton undergoes a nonanalytical jump at the end of inflation. Using smooth interpolating analytical forms of the coupling function, we show that such unphysical jump does not invalidate the main prediction of the model, which still represents a viable mechanism for explaining cosmic magnetization. Nevertheless, there is a spurious result associated with the nonanaliticity of the coupling, to wit, the prediction that the spectrum of created photons has a power-law decay in the ultraviolet regime. This issue is discussed using both semiclassical approximation and smooth coupling functions.