Generation of electromagnetic fields in string cosmology with a massive scalar field on the anti D-brane

TL;DR

This paper investigates how electromagnetic fields, specifically magnetic fields, can be generated during inflation in a string theory framework involving a massive scalar field on anti-D3 branes, potentially explaining cosmic magnetic fields.

Contribution

It demonstrates that coupling between gauge fields and a rolling scalar field in string-inspired models can produce magnetic fields strong enough to seed galactic dynamos, with implications for early universe magnetogenesis.

Findings

Magnetic fields at decoupling can exceed seed requirements for galactic dynamo.

Gauge fields are significantly amplified during inflation.

Reheating involves efficient gauge field production with energy density surpassing inflaton.

Abstract

We study the generation of electromagnetic fields in a string-inspired scenario associated with a rolling massive scalar field $\phi$ on the anti-D3 branes of KKLT de Sitter vacua. The 4-dimensional DBI type effective action naturally gives rise to the coupling between the gauge fields and the inflaton $\phi$, which leads to the production of cosmological magnetic fields during inflation due to the breaking of conformal invariance. We find that the amplitude of magnetic fields at decoupling epoch can be larger than the limiting seed value required for the galactic dynamo. We also discuss the mechanism of reheating in our scenario and show that gauge fields are sufficiently enhanced for the modes deep inside the Hubble radius with an energy density greater than that of the inflaton.