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arXiv · 2507.08774

The thermal backreaction of a scalar field in de Sitter spacetime

Nikos Irges·Antonis Kalogirou·Fotis Koutroulis
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Abstract

We argue that a scalar field in de Sitter spacetime should feel explicit thermal effects associated with its curvature. Starting from the Bunch-Davies vacuum and a scalar field with small mass compared to the de Sitter curvature, we use the thermo-field dynamics formalism in order to expose these thermal effects. We compute the thermal Wightman function connecting two spacetime points and from it, via the point-splitting regularization technique, the renormalized thermal energy-momentum tensor. We then examine how these corrections affect the de Sitter geometry by solving for the semi-classical backreaction and find that their sign depends on the initial conditions. In order to place our results in context, we compare them to the corresponding 2-loop quantum gravity correction to the cosmological constant derived in [1].

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Nikos Irges, Antonis Kalogirou, Fotis Koutroulis. 2025-12-05. The thermal backreaction of a scalar field in de Sitter spacetime. https://doi.org/10.1088/1402-4896%2Fae2441

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