The QCD moat regime and its real-time properties

TL;DR

This paper investigates the real-time properties of pions in dense QCD matter, revealing a moat regime characterized by a spectral peak at spacelike momentum and assessing the stability of homogeneous phases against inhomogeneous condensates.

Contribution

It introduces the concept of the moat regime in QCD, linking it to particle-hole fluctuations and the emergence of a new quasiparticle called the moaton, and evaluates phase stability at finite density.

Findings

Moat regime arises from particle-hole fluctuations near the Fermi surface.

Identification of a spectral peak indicating a new quasiparticle, the moaton.

Homogeneous chiral phase stability is unlikely for baryon chemical potentials ≤ 630 MeV.

Abstract

Dense QCD matter may exhibit crystalline phases. Their existence is reflected in a moat regime, where mesonic correlations feature spatial modulations. We study the realtime properties of pions at finite temperature and density in QCD in order to elucidate the nature of this regime. We show that the moat regime arises from particle-hole-like fluctuations near the Fermi surface. This gives rise to a characteristic peak in the spectral function of the pion at nonzero \emph{spacelike} momentum. This peak can be interpreted as a new quasi particle, the moaton. In addition, our framework also allows us to directly test the stability of the homogeneous chiral phase against the formation of an inhomogeneous condensate in QCD. We find that the formation of such a phase is highly unlikely for baryon chemical potentials $\mu_B \leq 630$\,MeV.