Density, short-range order and the quark-gluon plasma

TL;DR

This paper investigates the spatial correlator of the thermal energy density in the quark-gluon plasma, revealing its behavior at high temperatures and suggesting a dense, nearly conformal medium with weak short-range order.

Contribution

It provides lattice simulation results of the energy density correlator in SU(3) gauge theory across a range of temperatures, highlighting its non-monotonic behavior and near-conformal nature at high temperatures.

Findings

Correlator exhibits non-monotonic behavior with a broad maximum at r ≈ 0.6/T.

The medium is nearly conformal by 2T_c.

Suggests a dense medium with weak short-range order, similar to a near-critical fluid.

Abstract

We study the thermal part of the energy density spatial correlator in the quark-gluon plasma. We describe its qualitative form at high temperatures. We then calculate it out to distances approx. 1.5/T in SU(3) gauge theory lattice simulations for the range of temperatures 0.9<= T/T_c<= 2.2. The vacuum-subtracted correlator exhibits non-monotonic behavior, and is almost conformal by 2T_c. Its broad maximum at r approx. 0.6/T suggests a dense medium with only weak short-range order, similar to a non-relativistic fluid near the liquid-gas phase transition, where eta/s is minimal.