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Late-time correlators and complex geodesics in de Sitter space

Lars Aalsma, Mir Mehedi Faruk, Jan Pieter van der Schaar, Manus Visser, Job de Witte

SciPost Phys. 15, 031 (2023) · published 26 July 2023

Abstract

We study two-point correlation functions of a massive free scalar field in de Sitter space using the heat kernel formalism. Focusing on two operators in conjugate static patches we derive a geodesic approximation to the two-point correlator valid for large mass and at late times. This expression involves a sum over two complex conjugate geodesics that correctly reproduces the large-mass, late-time limit of the exact two-point function in the Bunch-Davies vacuum. The exponential decay of the late-time correlator is associated to the timelike part of the complex geodesics. We emphasize that the late-time exponential decay is in tension with the finite maximal entropy of empty de Sitter space, and we briefly discuss how non-perturbative corrections might resolve this paradox.

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