QCD Dirac Spectrum at Finite Chemical Potential: Anomalous Effective Action, Berry Phase and Composite Fermions

TL;DR

This paper models the QCD Dirac spectrum at finite chemical potential using a 2D effective action, revealing a droplet of eigenvalues with Berry phase and anomalous transport, hinting at Dirac composite fermions.

Contribution

It introduces a 2D effective action framework for the QCD Dirac spectrum at finite chemical potential, linking eigenvalue droplet behavior with Berry phase and composite fermion phenomena.

Findings

Eigenvalues form a droplet with screening and plasmon oscillations.

Presence of a magnetic vortex induces a Berry phase.

Anomalous transport suggests Dirac fermion behavior in composite fermions.

Abstract

We show that the QCD Dirac spectrum at finite chemical potential using a matrix model in the spontaneously broken phase, is amenable to a generic 2-dimensional effective action. The eigenvalues form a droplet with strong screening and plasmon oscillation. The droplet is threaded by a magnetic vortex which is at the origin of a Berry phase. For quarks in the complex or Dirac representation, the anomalous transport in the droplet of eigenvalues bear some similarities with that in droplets of composite fermions at half filling suggesting that the latters maybe Dirac fermions.