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arXiv · 1905.02714

Back(reaction) to the Future in the Unruh-de Sitter State

Lars Aalsma·Maulik Parikh·Jan Pieter van der Schaar
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Abstract

Motivated by black hole physics, we define the Unruh state for a scalar field in de Sitter space. Like the Bunch-Davies state, the Unruh-de Sitter state appears thermal to a static observer. However, it breaks some of the symmetries of de Sitter space. We calculate the expectation value of the energy-momentum tensor in the Unruh-de Sitter state in two dimensions and find a non-vanishing flux of outgoing negative energy. Extrapolating the result to four dimensions, we argue that this backreacts on the initial de Sitter geometry semi-classically. Notably, we estimate that de Sitter space is destabilized on a timescale set by the gravitational entropy; analogous to black hole evaporation, the endpoint of this instability is a singular geometry outside the regime of effective field theory. Finally, we suggest that the Unruh-de Sitter state may be a natural initial state for patches of de Sitter space, and discuss the implications for slow-roll and eternal inflation, and for de Sitter thermodynamics.

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Lars Aalsma, Maulik Parikh, Jan Pieter van der Schaar. 2019-05-07. Back(reaction) to the Future in the Unruh-de Sitter State. https://doi.org/10.1007/jhep11(2019)136

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