Microscopic origin of the entropy of de Sitter spacetime

TL;DR

This paper constructs a family of semiclassical de Sitter microstates using backreacted geometries with thin-shell branes and demonstrates that wormhole contributions lead to a state count matching the Gibbons-Hawking entropy, providing a microscopic understanding.

Contribution

It introduces a novel construction of de Sitter microstates and shows how wormhole effects account for the entropy, offering a microscopic derivation of Gibbons-Hawking entropy.

Findings

Microstates constructed via backreacted geometries with thin-shell branes.

Wormhole contributions yield universal overlaps between microstates.

Microstate count matches exponential of Gibbons-Hawking entropy.

Abstract

We construct an infinite family of semiclassical de Sitter (dS) microstates, realized as backreacted geometries of dS spacetime with a constant tension thin-shell brane located outside the dS event horizon. We further show that wormhole contributions to the semiclassical Euclidean gravitational path integral lead to universal nonperturbative overlaps between these microstates. By evaluating the nonperturbative overlaps, we count the dimension of the Hilbert space spanned by the semiclassical dS microstates and find that it precisely equals the exponential of the Gibbons-Hawking entropy of dS spacetime. Our construction thus provides a state-counting derivation for Gibbons-Hawking entropy of dS spacetime.