Two-colour QCD at non-zero quark-number density

TL;DR

This study simulates two-colour four-flavour QCD at non-zero quark chemical potential, revealing a second-order phase transition with diquark condensation and Goldstone bosons, consistent with effective theory predictions.

Contribution

It provides the first lattice simulation evidence of diquark condensation and spontaneous quark number breaking in two-colour QCD at finite density.

Findings

Diquark condensate forms for chemical potential above critical value

Transition is second order

Goldstone bosons are observed in the spectrum

Abstract

We have simulated two-colour four-flavour QCD at non-zero chemical potential $\mu$ for quark number. Simulations were performed on $8^4$ and $12^3 \times 24$ lattices. Clear evidence was seen for the formation of a colourless diquark condensate which breaks quark number spontaneously, for $\mu > \mu_c \sim m_\pi/2$. The transition appears to be second order. We have measured the spectrum of scalar and pseudoscalar bosons which shows clear evidence for the expected Goldstone boson. Our results are in qualitative agreement with those from effective Lagrangians for the potential Goldstone excitations of this theory.