Stochastic Baryogenesis

TL;DR

This paper explores how stochastic effects during inflation can lead to spontaneous CP violation and baryogenesis via the Affleck-Dine mechanism, explaining the observed matter-antimatter asymmetry.

Contribution

It introduces a multi-field stochastic approach to analyze the VEV distribution of a charged scalar during inflation, revealing spontaneous CP violation even in CP invariant models.

Findings

Stochastic inflationary VEVs can spontaneously break CP symmetry.

The model explains the observed baryon asymmetry for high inflation scales.

Charged scalar masses around the Hubble scale are favored by isocurvature constraints.

Abstract

Using a multi-field stochastic approach, we investigate the vacuum expectation value (VEV) during inflation of a scalar field charged under a mildly broken global $U(1)$ symmetry that can play the role of baryon or lepton number, or possibly a dark baryon number or a combination of the three. Even for a CP invariant Lagrangian, the stochastic distribution of inflationary VEVs in general breaks CP spontaneously, allowing for successful baryogenesis via the Affleck-Dine mechanism. For the Hubble scale during inflation $H_\ast$ as high as $10^{13}$ GeV, we show that the post-inflationary relaxation of the charged scalar with stochastic initial conditions can explain the observed baryon asymmetry, and that a charged scalar mass at the order of $H_\ast$ is favored by the isocurvature constraints.