Generating the Observed Baryon Asymmetry from the Inflaton Field

TL;DR

This paper introduces a novel mechanism where the inflaton field, modeled as a complex scalar with weak symmetry breaking, can generate the observed baryon asymmetry during inflation, with testable observational predictions.

Contribution

It presents a new version of the Affleck-Dine mechanism involving the inflaton, including detailed inflationary dynamics, decay processes, and particle physics embeddings.

Findings

The mechanism can produce the observed baryon asymmetry.

Predicted isocurvature fluctuations are near current detection limits.

Potential large-scale baryon density dipole could be observable.

Abstract

We propose a mechanism by which the inflaton can generate baryogenesis, by taking the inflaton to be a complex scalar field with a weakly broken global symmetry and present a new version of the Affleck-Dine mechanism. The smallness of the breaking is motivated both by technical naturalness and a requirement for inflation. We study inflation driven by a quadratic potential for simplicity and discuss generalizations to other potentials. We compute the inflationary dynamics and find that a conserved particle number is obtained towards the end of inflation. We then explain in detail the later decay to baryons. We present two promising embeddings in particle physics: (i) using high dimension operators for a gauge singlet; we find this leads to the observed asymmetry for decay controlled by the ~ grand unified theory scale and this is precisely the regime where the effective field theory applies. (ii) using a colored inflaton, which requires small couplings. We also point out two observational consequences: a possible large scale dipole in the baryon density, and a striking prediction of isocurvature fluctuations whose amplitude is found to be just below current limits and potentially detectable in future data.