A global picture of quantum de Sitter space

TL;DR

Perturbative gravity about de Sitter space is used to build a global, eternal de Sitter framework in which the physical state space is finite-dimensional and invariant under the de Sitter group. Physical states are obtained by group averaging of weakly back-reacting seed states, yielding a finite-dimensional H^f_phys whose size matches (and is below) the de Sitter entropy bound. Observables are defined relationally and regulated by cutoffs to suppress Boltzmann-brain type fluctuations, enabling local physics to emerge on timescales t << R S_dS. The work thus offers a coherent global picture that resolves the apparent tension between de Sitter symmetry and finite entropy and points to nonperturbative and holographic avenues for future research.

Abstract

Perturbative gravity about a de Sitter background motivates a global picture of quantum dynamics in `eternal de Sitter space,' the theory of states which are asymptotically de Sitter to both future and past. Eternal de Sitter physics is described by a finite dimensional Hilbert space in which each state is precisely invariant under the full de Sitter group. This resolves a previously-noted tension between de Sitter symmetry and finite entropy. Observables, implications for Boltzmann brains, and Poincare recurrences are briefly discussed.