Thermal ground state for pure SU(2) Yang-Mills thermodynamics

TL;DR

This paper reviews how a composite adjoint-scalar field, emerging from calorons and anti-calorons, influences the thermodynamics of pure SU(2) Yang-Mills theory, leading to a better understanding of the deconfinement transition.

Contribution

It introduces a gauge-invariant effective Lagrangian incorporating a composite scalar field that explains gluon mass generation and thermodynamic properties above the deconfinement temperature.

Findings

The composite field induces a thermal gluon mass via a Higgs mechanism.

The model predicts a linear temperature dependence of the trace anomaly.

Results align with recent lattice QCD data.

Abstract

In this proceeding the emergence of a composite, adjoint-scalar field as an average over (trivial holonomy) calorons and anti-calorons is reviewed. This composite field acts as a background field to the dynamics of perturbative gluons, to which is coupled via an effective, gauge invariant Lagrangian valid for temperatures above the deconfinement phase transition. Moreover, also an Higgs mechanism is induced by the composite field: two gluons acquire a quasi-particle thermal mass. On the phenomenological side the composite field acts as a bag pressure which shows a linear dependence on the temperature. As a result the linear rise with temperature of the trace anomaly is obtained and is compared to recent lattice studies.