Lattice Study of Dense Matter with Two Colors and Four Flavors

TL;DR

This study compares SU(2) lattice gauge theories with 2 and 4 flavors at finite chemical potential, revealing differences in gauge field smoothness and matter interactions, and identifying a phase of degenerate, confined baryonic matter.

Contribution

It provides the first detailed comparison of thermodynamic and phase properties between N_f=2 and N_f=4 flavors in dense SU(2) matter using lattice simulations.

Findings

Smaller string tension for N_f=4 indicates smoother gauge configurations.

Both theories show a phase with degenerate, confined baryonic matter.

N_f=4 matter remains relativistic and strongly-interacting at all mu above onset.

Abstract

We present results from a simulation of SU(2) lattice gauge theory with N_f=4 flavors of Wilson fermion and non-zero quark chemical potential mu, using the same 12^3x24 lattice, bare gauge coupling, and pion mass in cut-off units as a previous study with N_f=2. The string tension for N_f=4 is found to be considerably smaller implying smoother gauge field configurations. Thermodynamic observables and order parameters for superfluidity and color deconfinement are studied, and comparisons drawn between the two theories. Results for quark density and pressure as functions of mu are qualitatively similar for N_f=2 and N_f=4; in both cases there is evidence for a phase in which baryonic matter is simultaneously degenerate and confined. Results for the stress-energy tensor, however, suggest that while N_f=2 has a regime where dilute matter is non-relativistic and weakly-interacting, N_f=4 matter is relativistic and strongly-interacting for all values of mu above onset.