Cosmic QCD Epoch at Nonvanishing Lepton Asymmetry

TL;DR

This paper explores how a nonzero lepton asymmetry influences the early Universe's evolution through the QCD phase diagram, affecting chemical potentials and cosmic trajectories.

Contribution

It introduces a lattice QCD-based method to study the impact of lepton asymmetry on the QCD epoch's chemical potential evolution.

Findings

Lepton asymmetry significantly alters chemical potential trajectories.

Charge chemical potential can surpass baryon chemical potential with larger lepton asymmetry.

Standard cosmic trajectory assumes negligible lepton asymmetry.

Abstract

We investigate how a lepton asymmetry impacts the cosmic trajectory in the QCD phase diagram. We study the evolution of chemical potentials during the QCD epoch of the early Universe using susceptibilities from lattice QCD to interpolate between an ideal quark gas and an ideal hadron resonance gas. The lepton asymmetry affects the evolution of all chemical potentials. The standard cosmic trajectory is obtained assuming tiny lepton and baryon asymmetries. For larger lepton asymmetry, the charge chemical potential exceeds the baryon chemical potential before pion annihilation.