Time-dependent quantum correlations in two-dimensional expanding spacetime

TL;DR

This paper investigates how quantum correlations evolve over time in two-dimensional expanding universes using holographic models, revealing universal behaviors and a phenomenon of dethermalization after a critical time.

Contribution

It compares two distinct holographic models of expanding universes and uncovers their similar qualitative time-dependent quantum correlation behaviors, including dethermalization.

Findings

Holographic models show similar time-dependence in quantum correlations during eternal inflation.

In radiation era, a thermal system becomes dethermalized after a critical time.

Universal features of quantum entanglement evolution in expanding spacetimes.

Abstract

In expanding universes, the entanglement entropy must be time-dependent because the background geometry changes with time. For understanding time evolution of quantum correlations, we take into account two distinct holographic models, the dS boundary model and the braneworld model. In this work, we focus on two-dimensional expanding universes for analytic calculation and comparison. Although two holographic models realize expanding universes in totally different ways, we show that they result in the qualitatively same time-dependence for eternal inflation. We further investigate the time-dependent correlations in the radiation-dominated era of the braneworld model. Intriguingly, the holographic result reveals that a thermal system in the expanding universe is {\it dethermalized} after a critical time characterized by the subsystem size.