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Eternal inflation and energy conditions in de Sitter spacetime

Tanmay Vachaspati
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Abstract

Eternal inflation is shown to require violations of the Null Energy Condition (NEC) on superhorizon scales. With light scalar fields as the matter sources in a de Sitter background, there can be no classical or semiclassical violations of the NEC. However, quantum fluctuations of the energy-momentum tensor, described by an expectation value of four field operators, do lead to large-scale NEC violations. The backreaction of such quantum fluctuations on the inflating spacetime is generally deduced at a heuristic level and leads to the eternal inflation scenario. A rigorous treatment of the backreaction will necessarily include fluctuations of the metric, and several new effects are expected to come into play.

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Tanmay Vachaspati. 2003-05-22. Eternal inflation and energy conditions in de Sitter spacetime. https://arxiv.org/abs/astro-ph/0305439

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