Inflating Kahler Moduli and Primordial Magnetic Fields

TL;DR

This paper investigates the generation of primordial magnetic fields during inflation in type IIB string theory, focusing on Kahler moduli as inflatons and analyzing their coupling to gauge fields.

Contribution

It explicitly models the inflaton coupling to the Maxwell term in string inflation scenarios, exploring the implications for primordial magnetic field strength and scale dependence.

Findings

Primordial magnetic fields can be generated during Kahler moduli inflation.

The strength and scale dependence of these fields are determined by the inflaton coupling dynamics.

The strong coupling problem arises in certain fibre inflation models with D7-branes.

Abstract

We study the production of primordial magnetic fields in inflationary models in type IIB string theory where the role of the inflaton is played by a Kahler modulus. We consider various possibilities to realise the Standard Model degrees of freedom in this setting and explicitly determine the time dependence of the inflaton coupling to the Maxwell term in the models. Using this we determine the strength and scale dependence of the magnetic fields generated during inflation. The usual "strong coupling problem" for primordial magnetogesis manifests itself by cycle sizes approaching the string scale, this appears in a certain class of fibre inflation models where the standard model is realised by wrapping D7-branes on cycles in the geometric regime.