Phenomenological Models of the Quark-Gluon Plasma Equation of State

TL;DR

This paper introduces two phenomenological models for the SU(N) quark-gluon plasma's equation of state, matching lattice results and capturing phase transition behaviors with minimal parameters.

Contribution

It presents novel models based on high temperature expansions and color neutrality, providing insights into phase transitions and large-N limits of the quark-gluon plasma.

Findings

Models match lattice simulation behavior from T_d to 5T_d.

N=2 transition is second order; N=3,4,5 are first order.

Models exhibit a smooth large-N limit.

Abstract

Two phenomenological models describing an SU(N) quark-gluon plasma are presented. The first is obtained from high temperature expansions of the free energy of a massive gluon, while the second is derived by demanding color neutrality over a certain length scale. Each model has a single free parameter, exhibits behavior similar to lattice simulations over the range T_d-5T_d, and has the correct blackbody behavior for large temperatures. The N=2 deconfinement transition is second order in both models, while N=3,4, and 5 are first order. Both modelsappear to have a smooth large-N limit. In both models, the confined phase is characterized by a mutual repulsion of Polyakov loop eigenvalues that makes the Polyakov loop expectation value zero. In the deconfined phase, the rotation of the eigenvalues in the complex plane towards 1 is responsible for the approach to the blackbody limit over the range T_d-5T_d. The addition of quarks in SU(3) breaks Z(3) symmetry weakly and eliminates the deconfining phase transition for sufficiently light quarks.