Instanton dynamics in finite temperature QCD via holography

TL;DR

This paper uses holography to study instantons in finite temperature QCD, revealing stabilized instanton sizes, different dual topologies, and phase-dependent topological charge fluctuations, with a transition at the GWW point.

Contribution

It provides a holographic analysis of instanton dynamics in finite temperature QCD, highlighting phase-dependent behaviors and topological transitions.

Findings

Instanton sizes are stabilized in both phases.

Different topologies for large and small instantons in deconfinement.

Topological charge fluctuations are large in confinement, suppressed in deconfinement.

Abstract

We investigate instantons in finite temperature QCD via Witten's holographic QCD. To study the deconfinement phase, we use the setup proposed in [1] (arXiv:1107.4048). We find that the sizes of the instantons are stabilized at certain values both in the confinement and deconfinement phases. This agrees with the numerical result in the lattice gauge theory. Besides we find that the gravity duals of the large and small instantons in the deconfinement phase have different topologies. We also argue that the fluctuation of the topological charges is large in confinement phase while it is exponentially suppressed in deconfinement phase, and a continuous transition occurs at the Gross-Witten-Wadia (GWW) point. It would be difficult to observe the counterpart of this transition in lattice QCD, since the GWW point in QCD may stay at an unstable branch.