From in-Medium Color Forces to Transport Properties of QGP

TL;DR

This paper employs a quantum many-body T-matrix approach to study the spectral and transport properties of the quark-gluon plasma, revealing two potential scenarios and favoring the strongly-coupled one based on transport coefficients.

Contribution

It introduces a self-consistent T-matrix framework with two in-medium potential scenarios, comparing them to lattice-QCD data and heavy-ion phenomenology.

Findings

Two in-medium potential scenarios: weakly-coupled and strongly-coupled.

Transport coefficients favor the strongly-coupled scenario.

Bound states and spectral functions are analyzed near the critical temperature.

Abstract

A thermodynamic quantum many-body $T$-matrix approach is employed to study the spectral and transport properties of the quark-gluon plasma at moderate temperatures where nonperturbative effects are essential. For the partonic two-body interaction we utilize a QCD-inspired Hamiltonian whose color forces are motivated by the heavy-quark (HQ) limit including remnants of the confining force, and augmented by relativistic corrections. We solve the in-medium parton propagators and $T$-matrices selfconsistently and resum the skeleton diagrams for the equation of state (EoS) to all orders thereby accounting for the dynamical formation of two-body bound states. Two types solutions for the in-medium potential are found in when fitting to lattice-QCD data for the EoS, HQ free energy and quarkonium correlators: a weakly-coupled scenario (WCS) with a (real part of the) potential close to the free energy, resulting in moderately broadened spectral functions and weak bound states near $T_c$, and a strongly-coupled scenario (SCS), with a much stronger potential which produces large imaginary parts ("melting" the parton spectral functions) and generates strong bound states near $T_c$. We calculate pertinent transport coefficients (specific shear viscosity and HQ diffusion coefficient) and argue that their constraints from heavy-ion phenomenology unambiguously favor the strongly-coupled scenario.