# Entanglement and thermalization

## TL;DR

This paper explores how entanglement in quantum field theory can lead to apparent thermalization, explaining phenomena like the success of thermal models in particle collisions without requiring scatterings.

## Contribution

It demonstrates that entanglement entropy in an expanding relativistic string can produce thermal-like states, providing a new perspective on thermalization in quantum field systems.

## Key findings

- Entanglement entropy is extensive in rapidity at early times.
- Reduced density operator appears thermal with a specific entanglement temperature.
- Thermalization can occur without scatterings due to entanglement effects.

## Abstract

In a quantum field theory, apparent thermalization can be a consequence of entanglement as opposed to scatterings. We discuss here how this can help to explain open puzzles such as the success of thermal models in electron-positron collisions. It turns out that an expanding relativistic string described by the Schwinger model (which also underlies the Lund model) has at early times an entanglement entropy that is extensive in rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature $T_\tau=\hbar/(2\pi k_B\tau)$, even in the absence of any scatterings.