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arXiv · 2603.29538

Density matrix of de Sitter JT gravity

Wilfried Buchmuller·Alexander Westphal
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Abstract

Jackiw-Teitelboim (JT) gravity in two-dimensional de Sitter space is an intriguing toy model for a quantum mechanical description of an inflationary phase of the universe, including initial conditions. Starting from exact solutions of the Wheeler-DeWitt equation, we study a conditional density matrix of the system. We find that the ground state is a mixed state, rather than a pure Hartle-Hawking state. Our results are consistent with the semiclassical double-trumpet amplitude, and with recent work on complex geometries containing bra-ket wormholes. We also analyze semiclassical wave functions for metric, dilaton, and an additional inflaton field. The probability distribution for the size of the universe is flat.

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Wilfried Buchmuller, Alexander Westphal. 2026-03-31. Density matrix of de Sitter JT gravity. https://arxiv.org/abs/2603.29538

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