https://doi.org/10.1140/epjc/s10052-024-12590-3
Regular Article - Theoretical Physics
Back-reaction of long-wavelength cosmological fluctuations as measured by a clock field
1
Department of Physics, McGill University, H3A 2T8, Montréal, QC, Canada
2
Institute for Theoretical Physics, ETH Zürich, Switzerland
Received:
9
July
2023
Accepted:
19
February
2024
Published online:
15
March
2024
We consider the back-reaction of cosmological fluctuations on the local expansion rate averaged over a space-like hypersurface of constant value of a clock field. We show that in the infrared limit, the fluctuations lead to a decrease in the average expansion rate, measured at a fixed value of the clock field, compared to what would be obtained in a homogeneous universe. We work in the context of Einstein gravity coupled to perfect fluid matter.
© The Author(s) 2024
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