Rotor Spectra and Berry Phases in the Chiral Limit of QCD on a Torus

TL;DR

This paper investigates the finite-volume spectra of QCD in the chiral limit, revealing rotor spectra influenced by Berry phases and monopole fields, and connects these phenomena to solutions of Yang-Mills-Chern-Simons equations.

Contribution

It provides a detailed analysis of spontaneous chiral symmetry breaking in QCD on a torus, highlighting the role of Berry phases and monopole fields in the dynamics.

Findings

Rotor spectra arise from spontaneous symmetry breaking.

Berry phases affect the motion of the chiral order parameter.

The Berry gauge field solves a Yang-Mills-Chern-Simons equation.

Abstract

We consider the finite-volume spectra of QCD in the chiral limit of massless up and down quarks and massive strange quarks in the baryon number sectors $B = 0$ and $B = 1$ for different values of the isospin. Spontaneous symmetry breaking gives rise to rotor spectra, as the chiral order parameter precesses through the vacuum manifold. Baryons of different isospin influence the motion of the order parameter through non-trivial Berry phases and associated abstract monopole fields. Our investigation provides detailed insights into the dynamics of spontaneous chiral symmetry breaking in QCD on a torus. It also sheds new light on Berry phases in the context of quantum field theory. Interestingly, the Berry gauge field resulting from QCD solves a Yang-Mills-Chern-Simons equation of motion on the vacuum manifold $SU(2) = S^3$.