Generation of large scale magnetic fields by coupling to curvature and dilaton field

TL;DR

This paper explores how coupling quantum fluctuations to the dilaton field and curvature during inflation can generate large-scale magnetic fields consistent with current observations.

Contribution

It introduces a model where magnetic fields are produced via coupling to the dilaton and Ricci scalar during inflation, considering different dilaton evolution scenarios.

Findings

Magnetic fields of observed strength can be generated during inflation.

Both dilaton decay scenarios produce viable magnetic fields.

The model aligns with current cosmological magnetic field observations.

Abstract

We investigate the generation of large scale magnetic fields in the universe from quantum fluctuations produced in the inflationary stage. By coupling these quantum fluctuations to the dilaton field and Ricci scalar, we show that the magnetic fields with the strength observed today can be produced. We consider two situations: First, the evolution of dilaton ends at the onset of the reheating stage. Second, the dilaton continues its evolution after reheating and then decays. In both cases, we come back to the usual Maxwell equations after inflation and then calculate present magnetic fields.