Leptogenesis via Varying Weinberg Operator: the Closed-Time-Path Approach

TL;DR

This paper introduces a novel leptogenesis mechanism via a spacetime-varying Weinberg operator during a first order phase transition, using non-equilibrium quantum field theory to calculate the resulting baryon asymmetry.

Contribution

It proposes the CP violating phase transition mechanism for leptogenesis, analyzing the effects of bubble wall dynamics and thermal effects with a detailed quantum field theory approach.

Findings

Lepton asymmetry is generated through interference of spacetime-varying Weinberg operators.

Bubble wall properties significantly influence the magnitude of asymmetry.

Thermal effects modify the efficiency of the CP violating process.

Abstract

In this work we provide a detailed study of the CP violating phase transition (CPPT) which is a new mechanism proposed to produce a baryon asymmetry. This mechanism exploits the Weinberg operator whose coefficient is dynamically realised from the vacuum expectation values (VEVs) of new scalars. In the specific case of the first order phase transition, the scalar VEVs vary in the bubble wall which separates the two phases. This results in a spacetime varying coefficient for the Weinberg operator. The interference of two Weinberg operators at different spacetime points generates a CP asymmetry between lepton and anti-lepton production/annihilation processes, which eventually results in an asymmetry between baryon and anti-baryon number densities in the early Universe. We present the calculation of the lepton asymmetry, based on non-equilibrium quantum field theory methods, in full. We consider the influence of the bubble wall characteristics and the impact of thermal effects on the lepton asymmetry and draw a comparison between the CPPT mechanism and electroweak baryogenesis.