Quantum thermalization of Quark-Gluon Plasma

TL;DR

This paper uses quantum simulations of a simplified QCD model to explore how quark-gluon plasma thermalizes, revealing the roles of strong coupling, quantum scars, and topological effects in the thermalization process.

Contribution

It presents a first-principles quantum simulation approach to study real-time thermalization in a QCD-like system, highlighting the impact of coupling strength and topological vacuum states.

Findings

Quantum thermalization emerges at strong coupling.

Thermalization fails with increased quantum many-body scars.

Topological vacuum significantly influences thermalization behavior.

Abstract

The thermalization of quark gluon plasma created in relativistic heavy-ion collisions is a crucial theoretical question in understanding the onset of hydrodynamics, and in a broad sense, a key step to the exploration of thermalization in isolated quantum systems. Addressing this problem theoretically, in a first principle manner, requires a real-time, non-perturbative method. To this end, we carry out a fully quantum simulation on a classical hardware, of a massive Schwinger model, which well mimics QCD as it shares the important properties such as confinement and chiral symmetry breaking. We focus on the real-time evolution of the Wigner function, namely, the two-point correlation function, which approximates quark momentum distribution. In the context of the eigenstate thermalization hypothesis and the evolution of entropy, our solution reveals the emergence of quantum thermalization in quark-gluon plasma with a strong coupling constant, while thermalization fails progressively as a consequence of the gradually increased significance of quantum many-body scar states in a more weakly coupled system. More importantly, we observe the non-trivial role of the topological vacuum in thermalization, as the thermalization properties differ dramatically in the parity-even and parity-odd components of the Wigner function.