Chiral symmetry in strongly interacting matter

TL;DR

This paper reviews the role of chiral symmetry in strongly interacting matter, discussing its breaking, phase transitions, and the interplay between chiral and deconfinement transitions using effective models and lattice QCD comparisons.

Contribution

It provides a comprehensive overview of chiral symmetry phenomena in QCD, combining effective field theory and PNJL models with lattice results.

Findings

Chiral condensate varies with temperature and density.

Chiral and deconfinement transitions are entangled in models.

Comparisons with lattice QCD support model predictions.

Abstract

This is a brief summary of topics that were presented as lectures within the programme "New Frontiers in QCD 2010" at the Yukawa Institute of Theoretical Physics in Kyoto. The basic subject is phases and symmetry breaking patterns as they emerge from the approximate chiral symmetry of QCD. Part I focuses on the QCD interface with nuclear physics via chiral effective field theory. This includes nuclear thermodynamics and, in particular, constraints for compressed and hot baryonic matter provided by the density and temperature dependence of the chiral condensate. Part II explores aspects of the QCD phase diagram using a non-local improved version of the Polyakov - Nambu - Jona-Lasinio (PNJL) model. A prominent feature of such an approach is the occurence of a dynamical entanglement between chiral and deconfinement crossover transitions. Comparisons with available results from lattice QCD thermodynamics will be made.