# CP Violation at the Finite Temperature

## TL;DR

This paper investigates spontaneous CP violation at finite temperature, showing it can occur during the electroweak phase transition and potentially explain matter-antimatter asymmetry without conflicting with EDM constraints.

## Contribution

It proposes a scenario where spontaneous CP violation arises only around the electroweak phase transition, avoiding EDM constraints and aiding electroweak baryogenesis.

## Key findings

- CP-violating phase emerges near electroweak transition
- No extra CP violation needed beyond spontaneous mechanism
- Restoration of CP symmetry after transition

## Abstract

In this letter we explore the spontaneous CP violation at the finite temperature. We show that the CP-violating phase $\varphi$ may only emerge around the time of the electroweak phase transition, and it can provide a scource for generating the matter-antimatter asymmetry of the universe via the electroweak baryogenesis mechanism (EWBG) if the domain wall relating to $\pm \varphi$ vacuums is collapsed by a small explicit $Z_2$-breaking term. No extra CP violation is needed! The spontaneous CP is restored after the electroweak phase transition, such that there is no constraint from the electric dipole moment (EDM) measurements. This scenario resolves the tension between the non-observation of EDMs in precision measurement experiments and the requirement of a large CP violation by the EWBG.