Relating Quark Confinement and Chiral Symmetry Breaking in QCD

TL;DR

This paper explores the relationship between quark confinement and chiral symmetry breaking in QCD, showing that low-lying Dirac eigenmodes are crucial for chiral symmetry but negligible for confinement, indicating their independence.

Contribution

It provides a spectral analysis linking confinement indicators to Dirac eigenmodes, revealing their independence from chiral symmetry breaking in QCD.

Findings

Low-lying Dirac modes are essential for chiral symmetry breaking.

Confinement indicators are negligibly affected by low-lying Dirac modes.

Confinement and chiral symmetry breaking can occur independently.

Abstract

We study the relation between quark confinement and chiral symmetry breaking in QCD. Using lattice QCD formalism, we analytically express the various "confinement indicators", such as the Polyakov loop, its fluctuations, the Wilson loop, the inter-quark potential and the string tension, in terms of the Dirac eigenmodes. In the Dirac spectral representation, there appears a power of the Dirac eigenvalue $\lambda_n$ such as $\lambda_n^{N_t-1}$, which behaves as a reduction factor for small $\lambda_n$. Consequently, since this reduction factor cannot be cancelled, the low-lying Dirac eigenmodes give negligibly small contribution to the confinement quantities,while they are essential for chiral symmetry breaking. These relations indicate no direct, one-to-one correspondence between confinement and chiral symmetry breaking in QCD. In other words, there is some independence of quark confinement from chiral symmetry breaking, which can generally lead to different transition temperatures/densities for deconfinement and chiral restoration. We also investigate the Polyakov loop in terms of the eigenmodes of the Wilson, the clover and the domain-wall fermion kernels, respectively, and find the similar results. The independence of quark confinement from chiral symmetry breaking seems to be natural, because confinement is realized independently of quark masses and heavy quarks are also confined even without the chiral symmetry.