Particle asymmetries in the early universe

TL;DR

This paper explores how large lepton asymmetries in the early universe can significantly alter cosmic evolution, affecting relic abundances and the dynamics of the QCD transition.

Contribution

It introduces new insights into the effects of large lepton asymmetries on early universe processes and the QCD transition dynamics.

Findings

Large lepton asymmetries can modify the relic abundance of WIMPs.

Asymmetries of order unity in a single flavor impact early universe dynamics.

Large lepton asymmetries influence the cosmic QCD transition.

Abstract

The total lepton asymmetry $l=\sum_f l_f$ in our universe is only poorly constrained by theories and experiments. It might be orders of magnitudes larger than the observed baryon asymmetry $b\simeq {\cal O}(10^{-10})$, $|l|/b \leq {\cal O}(10^{9})$. We found that the dynamics of the cosmic QCD transition changes for large asymmetries. Predictions for asymmetries in a single flavour $l_f$ allow even larger values. We find that asymmetries of $l_f\leq {\cal O}(1)$ in a single or two flavours change the relic abundance of WIMPs. However, large lepton and large individual lepton flavour asymmetries influences significantly the dynamics of the early universe.