The quark-gluon-plasma phase transition diagram, Hagedorn matter and quark-gluon liquid

TL;DR

This paper develops a comprehensive model of the hadronic density of states across the ($$-T) phase diagram, explaining phenomena like the tri-critical point, quarkyonic matter, and the quark-gluon liquid through various internal symmetries and phase transitions.

Contribution

It introduces a unified model for high-lying mass spectra with different internal symmetries, explaining phase transitions and the tri-critical point in the QCD phase diagram.

Findings

The model explains the origin of the tri-critical point.

Different internal symmetries dominate at various phases.

Phase transitions include first order and higher order deconfinement.

Abstract

In order to study the nuclear matter in the relativistic heavy ion collisions and the compact stars, we need the hadronic density of states for the entire ($\mu_B-T$) phase transition diagram. We present a model for the continuous high-lying mass (and volume) spectrum density of states that fits the Hagedorn mass spectrum. This model explains the origin of the tri-critical point besides various phenomena such as the quarkyonic matter and the quark-gluon liquid. The Hagedorn mass spectrum is derived for the color-singlet quark-gluon bag with various internal structures such as the unimodular unitary, orthogonal and color-flavor locked symplectic symmetry groups. The continuous high-lying hadronic mass spectrum is populated at first by the unitary Hagedorn states. Then the spectrum turns to be dominated by the colorless orthogonal states as the dilute system is heated up. Subsequently, the liquid/gas of orthogonal Hagedorn states undergoes higher order deconfinement phase transition to quark-gluon plasma. Under the deconfinement phase transition process, the color-singlet states is broken badly to form the colored $SU(N_c)$ symmetry group. On the other hand, when the hadronic matter is compressed to larger $\mu_{B}$ and heated up, the colorless unitary states undergoes first order phase transition to explosive quark-gluon plasma. The tri-critical point emerges as a change in the characteristic behaviour of the matter and as an intersection among various phases with different internal symmetries. When the saturated hadronic matter is cooled down and compressed to higher density, it turns to be dominated by the colorless symplectic states. This matter exhibits the first order phase transition to quark-gluon plasma when it is heated up to higher temperature. The role of chiral phase transition is also discussed.