Eur. Phys. J. Spec. Top. (2021) 230: 1645-1657
https://doi.org/10.1140/epjs/s11734-021-00147-4

Review

Light quarks at finite temperature: chiral restoration and the fate of the $U{(1)}_A$ symmetry

Departamento de Física Teórica and IPARCOS, University Complutense, 28040, Madrid, Spain

^a gomez@ucm.es

Received: 30 November 2020
Accepted: 10 May 2021
Published online: 28 May 2021

Abstract

We review recent results on the role of light quark states within the QCD phase diagram. In particular, we will discuss how the combined use of theoretical techniques such as Effective Theories, Unitarization and Ward Identities helps to shed light on several important issues regarding chiral symmetry restoration, building bridges with recent lattice analyses. Special attention will be paid to the role of chiral and $U{(1)}_A$ partners in the interplay between those symmetries, which is crucial to properly understand the transition pattern. Light scalar mesons at finite temperature will be shown to be responsible for the description of susceptibilities encoding chiral and $U{(1)}_A$ restoration properties.