Free caloron gas in high temperature quenched QCD

TL;DR

This paper investigates the behavior of topological objects, likely calorons, in high temperature quenched QCD, showing they form a dilute, non-interacting gas above the phase transition using overlap Dirac operator measurements.

Contribution

It demonstrates how to extract the distribution of topological charges from the overlap Dirac spectrum and provides evidence for a dilute gas of calorons in high temperature QCD.

Findings

Number distributions are consistent with an ideal gas of non-interacting objects.

Overlap Dirac operator effectively measures topological charge and object counts.

Topological susceptibility decreases sharply across the transition.

Abstract

Across the finite temperature transition to the quark-gluon plasma, the QCD topological susceptibility decreases sharply. Thus in the high temperature phase the remaining topological objects (possibly calorons) form a weakly interacting dilute gas. The overlap Dirac operator, through its exact zero modes, allows one to measure the net topological charge. We show that separately the number of positively and negatively charged topological objects can also be extracted from the low end of the overlap Dirac spectrum. We find that slightly above the phase transition their number distributions are already consistent with an ideal gas of non-interacting topological objects.