Dirac Spectra and Real QCD at Nonzero Chemical Potential

TL;DR

This paper demonstrates that QCD Dirac spectra at various chemical potentials can be derived from a chiral Lagrangian, revealing a superfluid phase transition with a tricritical point in two-color QCD.

Contribution

It introduces a method to obtain Dirac spectra from a chiral Lagrangian at nonzero chemical potential and analyzes the phase diagram including a tricritical point.

Findings

Dirac spectra can be derived from a chiral Lagrangian at nonzero chemical potential.

A superfluid phase transition occurs beyond a critical chemical potential.

A tricritical point exists in the phase diagram of two-color QCD.

Abstract

We show that QCD Dirac spectra well below Lambda_{QCD}, both at zero and at nonzero chemical potential, can be obtained from a chiral Lagrangian. At nonzero chemical potential Goldstone bosons with nonzero baryon number condense beyond a critical value. Such superfluid phase transition is likely to occur in any system with a chemical potential with the quantum numbers of the Goldstone bosons. We discuss the phase diagram for one such system, QCD with two colors, and show the existence of a tricritical point in an effective potential approach.