Topological observables and domain wall tension from finite temperature chiral perturbation theory
arXiv:2603.04116
Abstract
Within the framework of SU(2) chiral perturbation theory, we derive the general solution of the QCD -vacuum for an arbitrary vacuum phase, explicitly incorporating isospin-breaking effects from the light quark mass difference, and compute the temperature dependence of the topological susceptibility, higher-order cumulants, and the domain wall tension up to next-to-leading order. We find that the topological susceptibility agrees with lattice data at low temperatures but deviates at higher temperatures as expected from the breakdown of the chiral expansion; moreover, we demonstrate that the normalized fourth-order cumulant and the domain wall tension decrease monotonically with increasing temperature, while the normalized sixth-order cumulant exhibits the opposite behavior. These results extend earlier analyses by showing how isospin breaking reshapes the full hierarchy of topological charge cumulants and the dynamics of -vacuum domain walls, thereby offering new theoretical input on the -vacuum properties, which are relevant for axion-related effective theories in hot QCD matter.
9 pages, 5 figures, 1 table. Accepted for publication in Physical Review D