Two-colour QCD at finite fundamental quark-number density and related theories

TL;DR

This paper simulates SU(2) Yang-Mills theory with four dynamical quark flavours at finite chemical potential, observing a phase transition with diquark condensation and analyzing the resulting Goldstone boson spectrum, providing insights relevant to QCD at finite density.

Contribution

It presents the first detailed lattice simulation of SU(2) QCD with four flavours at finite chemical potential, revealing phase transition behavior and symmetry breaking phenomena.

Findings

Observation of a phase transition to a diquark condensed state at high chemical potential

Evidence for a Goldstone boson resulting from spontaneous symmetry breaking

Analysis of light scalar and pseudoscalar boson spectra in the broken phase

Abstract

We are simulating SU(2) Yang-Mills theory with four flavours of dynamical quarks in the fundamental representation of SU(2) `colour' at finite chemical potential, mu for quark number, as a model for QCD at finite baryon number density. In particular we observe that for mu large enough this theory undergoes a phase transition to a state with a diquark condensate which breaks quark-number symmetry. In this phase we examine the spectrum of light scalar and pseudoscalar bosons and see evidence for the Goldstone boson associated with this spontaneous symmetry breaking. This theory is closely related to QCD at finite chemical potential for isospin, a theory which we are now studying for SU(3) colour.