Strong coupling methods in QCD thermodynamics

TL;DR

This paper reviews the application of strong coupling methods in lattice QCD thermodynamics, highlighting their role in understanding finite density physics and phase transitions, especially where numerical methods face challenges.

Contribution

It systematically discusses how strong coupling expansions provide qualitative and quantitative insights into QCD thermodynamics and phase transitions, complementing numerical approaches.

Findings

Emergence of the hadron resonance gas model

Identification of the onset transition to baryon matter

Quantitative determination of the deconfinement transition in Yang-Mills theory

Abstract

For a long time, strong coupling expansions have not been applied systematically in lattice QCD thermodynamics, in view of the succes of numerical Monte Carlo studies. The persistent sign problem at finite baryo-chemical potential, however, has motivated investigations using these methods, either by themselves or combined with numerical evaluations, as a route to finite density physics. This article reviews the strategies, by which a number of qualitative insights have been attained, notably the emergence of the hadron resonance gas or the identification of the onset transition to baryon matter in specific regions of the QCD parameter space. For the simpler case of Yang-Mills theory, the deconfinement transition can be determined quantitatively even in the scaling region, showing possible prospects for continuum physics.