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Title: Microscopic count of de Sitter horizon entropy
Plain: The horizon of an expanding universe has an entropy proportional to its area, just like a black hole. Which quantum states it counts is unknown.
Precise: The Gibbons-Hawking entropy of a d-dimensional de Sitter horizon is $S = A c^3/(4 G \hbar)$ with $k_B = 1$. Find a statistical system whose state count reproduces S including the one-loop logarithmic correction computed by Anninos, Denef, Law and Sun (2020).
Settled by: A microscopic system with a derived match of the leading area term and the logarithmic correction.
Kind: well-posed
Answer type: identification
References: (empty)
Literature status: open
Status note: The static-patch algebra of observables was shown to be of von Neumann type $\mathrm{II}_{1}$ with a maximum-entropy state (Chandrasekaran, Longo, Penington, Witten 2022), without a microscopic count.
Posed since: 1977