Hartle-Hawking state is a maximum of entanglement entropy

TL;DR

The paper demonstrates that the Hartle-Hawking state maximizes entanglement entropy among pure states with finite backreaction, positioning it as a curved-space analogue of the EPR state.

Contribution

It establishes the Hartle-Hawking state as a maximum entanglement entropy state in curved spacetime, extending the understanding of quantum entanglement in gravitational contexts.

Findings

Hartle-Hawking state is a maximum of entanglement entropy.

This state is analogous to the EPR state in curved spacetime.

Maximization occurs under the condition of finite backreaction.

Abstract

It is shown that the Hartle-Hawking state of a scalar field is a maximum of entanglement entropy in the space of pure quantum states satisfying the condition that backreaction is finite. In other words, the Hartle-Hawking state is a curved-space analogue of the EPR state, which is also a maximum of entanglement entropy.