Dirac spectrum in the chirally symmetric phase of a gauge theory. I

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Main Author: Giordano, Matteo
Format: Preprint
Published: 2025
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author Giordano, Matteo
author_facet Giordano, Matteo
contents I study the consequences of chiral symmetry restoration for the Dirac spectrum in finite-temperature gauge theories in the two-flavor chiral limit, using Ginsparg--Wilson fermions on the lattice. I prove that chiral symmetry is restored at the level of the susceptibilities of scalar and pseudoscalar bilinears if and only if all these susceptibilities do not diverge in the chiral limit $m\to 0$, with $m$ the common mass of the light fermions. This implies in turn that they are infinitely differentiable functions of $m^2$ at $m=0$, or $m$ times such a function, depending on whether they contain an even or odd number of isosinglet bilinears. Expressing scalar and pseudoscalar susceptibilities in terms of the Dirac spectrum, I use their finiteness in the symmetric phase to derive constraints on the spectrum, and discuss the resulting implications for the fate of the anomalous $\mathrm{U}(1)_A$ symmetry in the chiral limit. I also discuss the differentiability properties of spectral quantities with respect to $m^2$, and show from first principles that the topological properties of the theory in the chiral limit are characterized by an instanton gas-like behavior if $\mathrm{U}(1)_A$ remains effectively broken.
format Preprint
id arxiv_https___arxiv_org_abs_2510_24381
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Dirac spectrum in the chirally symmetric phase of a gauge theory. I
Giordano, Matteo
High Energy Physics - Lattice
High Energy Physics - Phenomenology
High Energy Physics - Theory
I study the consequences of chiral symmetry restoration for the Dirac spectrum in finite-temperature gauge theories in the two-flavor chiral limit, using Ginsparg--Wilson fermions on the lattice. I prove that chiral symmetry is restored at the level of the susceptibilities of scalar and pseudoscalar bilinears if and only if all these susceptibilities do not diverge in the chiral limit $m\to 0$, with $m$ the common mass of the light fermions. This implies in turn that they are infinitely differentiable functions of $m^2$ at $m=0$, or $m$ times such a function, depending on whether they contain an even or odd number of isosinglet bilinears. Expressing scalar and pseudoscalar susceptibilities in terms of the Dirac spectrum, I use their finiteness in the symmetric phase to derive constraints on the spectrum, and discuss the resulting implications for the fate of the anomalous $\mathrm{U}(1)_A$ symmetry in the chiral limit. I also discuss the differentiability properties of spectral quantities with respect to $m^2$, and show from first principles that the topological properties of the theory in the chiral limit are characterized by an instanton gas-like behavior if $\mathrm{U}(1)_A$ remains effectively broken.
title Dirac spectrum in the chirally symmetric phase of a gauge theory. I
topic High Energy Physics - Lattice
High Energy Physics - Phenomenology
High Energy Physics - Theory
url https://arxiv.org/abs/2510.24381