Entanglement and Fast Quantum Thermalization in Heavy Ion Collisions

TL;DR

This paper explores how entanglement entropy growth explains rapid thermalization in heavy ion collisions, linking quantum information concepts with gauge-gravity duality to understand the dynamics of thermalization.

Contribution

It connects entanglement entropy dynamics with fast thermalization in heavy ion collisions using gauge-gravity duality, providing a quantum information perspective.

Findings

Entanglement entropy increases rapidly during collisions.

Typical states in the Hilbert space lead to nearly thermal reduced states.

Gauge-gravity duality relates entanglement entropy to extremal surface areas.

Abstract

Let $A$ be subsystem of a larger system $A \cup B$, and $\psi$ be a typical state from the subspace of the Hilbert space ${\cal H}_{AB}$ satisfying an energy constraint. Then $\rho_A(\psi)= {\rm Tr}_B | \psi \rangle \langle \psi |$ is nearly thermal. We discuss how this observation is related to fast thermalization of the central region ($\approx A$) in heavy ion collisions, where $B$ represents other degrees of freedom (soft modes, hard jets, collinear particles) outside of $A$. Entanglement between the modes in $A$ and $B$ plays a central role: the entanglement entropy $S_A$ increases rapidly in the collision. In gauge-gravity duality, $S_A$ is related to the area of extremal surfaces in the bulk, which can be studied using gravitational duals.