Cold, dense matter via the lattice NJL model

TL;DR

This study uses lattice NJL model simulations to explore cold, dense quark matter, revealing a crossover transition, BCS superfluidity, and a consistent energy gap at high chemical potential.

Contribution

First lattice NJL simulations at non-zero chemical potential showing evidence of BCS superfluidity and a stable energy gap in cold, dense quark matter.

Findings

Chiral condensate indicates a crossover transition.

Presence of a non-zero diquark condensate at high chemical potential.

Energy gap is about 15% of the vacuum fermion mass, independent of chemical potential.

Abstract

We simulate the lattice Nambu--Jona-Lasinio (NJL) model in 3+1-dimensions at non-zero baryon chemical potential (mu) and zero temperature (T) and treat the results as phenomenologically relevant for cold, dense quark matter. Measurements of the chiral condensate indicate a crossover in the thermodynamic limit, whilst at high chemical potential and zero temperature we observe a non-zero diquark condensate and a gap in the fermion dispersion relation, which together provide evidence for BCS superfluidity. In particular, the size of gap is found to be approximately 15% the value of the vacuum fermion mass and roughly independent of mu in the chirally restored phase.