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arXiv · 2512.13221

Beyond general relativity: probing gravity with gravitational redshifts

Eleni Tsaprazi·Giorgio F. Lesci·Federico Marulli·Alan F. Heavens·Piero Rosati·Sofia Contarini·Enrico A. Maraboli·Pratika Dayal·Ofer Lahav·Lauro Moscardini
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Abstract

Despite the success of general relativity (GR), the unexplained nature of dark energy on cosmological scales leaves open the question of whether GR provides a complete description of gravity. This quest is further motivated by growing tensions among cosmological observations when interpreted within $Λ$CDM. Gravitational redshifts of cluster member galaxies probe cluster potentials on megaparsec scales directly, complementing conventional large-scale structure tests. Here, we investigate how redshift precision and survey design propagate into constraints on modified gravity using an end-to-end pipeline run on mock catalogues, focusing on mis-centring and spectroscopic completeness. We find that competitive measurements require wide-field spectroscopic cluster surveys explicitly designed to maximise the number of spectroscopically confirmed members per cluster, to enable high-purity stacking, and to control systematic effects.

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Eleni Tsaprazi, Giorgio F. Lesci, Federico Marulli, Alan F. Heavens, Piero Rosati, Sofia Contarini, Enrico A. Maraboli, Pratika Dayal, Ofer Lahav, Lauro Moscardini. 2025-12-15. Beyond general relativity: probing gravity with gravitational redshifts. https://arxiv.org/abs/2512.13221

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