Anisotropic Goldstone bosons of strong-coupling lattice QCD at high density

TL;DR

This paper investigates the spectrum of Goldstone bosons in strong-coupling lattice QCD at high baryon density, revealing anisotropic dispersion relations and two types of massless excitations with different dispersions.

Contribution

It introduces a next-nearest-neighbor fermion formulation preserving chiral symmetry and characterizes the anisotropic Goldstone bosons in dense lattice QCD.

Findings

Identified two types of Goldstone bosons with linear and quadratic dispersions.

Discovered that dispersion relations can become anisotropic depending on parameters.

Some bosons change type from II to I as conditions vary.

Abstract

We calculate the spectrum of excitations in strong-coupling lattice QCD in a background of fixed baryon density, at a substantial fraction of the saturation density. We employ a next-nearest-neighbor fermion formulation that possesses the SU(N_f)xSU(N_f) chiral symmetry of the continuum theory. We find two types of massless excitations: type I Goldstone bosons with linear dispersion relations and type II Goldstone bosons with quadratic dispersion relations. Some of the type I bosons originate as type II bosons of the nearest-neighbor theory. Bosons of either type can develop anisotropic dispersion relations, depending on the value of N_f and the baryon density.