Generation of large-scale magnetic fields, non-Gaussianity, and primordial gravitational waves in inflationary cosmology

TL;DR

This paper investigates how inflationary cosmology models, inspired by string theory, can generate large-scale magnetic fields, non-Gaussianity, and gravitational waves, aligning with observational data.

Contribution

It introduces a moduli inflation model breaking conformal invariance to produce observable magnetic fields, non-Gaussianity, and gravitational waves consistent with Planck data.

Findings

Magnetic field strength below back reaction limits

Non-Gaussianity within Planck constraints

Tensor-to-scalar ratio compatible with observations

Abstract

The generation of large-scale magnetic fields in inflationary cosmology is explored, in particular, in a kind of moduli inflation motivated by racetrack inflation in the context of the Type IIB string theory. In this model, the conformal invariance of the hypercharge electromagnetic fields is broken thanks to the coupling of both the scalar and pseudoscalar fields to the hypercharge electromagnetic fields. The following three cosmological observable quantities are first evaluated: The current magnetic field strength on the Hubble horizon scale, which is much smaller than the upper limit from the back reaction problem, local non-Gaussianity of the curvature perturbations due to the existence of the massive gauge fields, and the tensor-to-scalar ratio. It is explicitly demonstrated that the resultant values of local non-Gaussianity and the tensor-to-scalar ratio are consistent with the Planck data.