No evidence for modifications of gravity from galaxy motions on cosmological scales. (December 2018)

• Record Type: Journal Article
• Authors: He, Jian-hua; Guzzo, Luigi; Li, Baojiu; Baugh, Carlton
• Is Part Of: Nature astronomy. Volume 2:Number 12(2018)
• Page Start: 967
• Page End: 972
• Publication Date: 2018-12
• Subjects: Astronomy -- Periodicals; 520.5
• DOI: 10.1038/s41550-018-0573-2
• Languages: English
• ISSNs: 2397-3366

Abstract

Abstract Current tests of general relativity (GR) remain confined to the scale of stellar systems or the strong gravity regime. A departure from GR on cosmological scales has been advocated1 as an alternative to the cosmological constantΛ (ref. 2 ) to account for the observed cosmic expansion history3, 4 . However, such models yield distinct values for the linear growth rate of density perturbations and consequently for the associated galaxy peculiar velocity field. Measurements of the resulting anisotropy of galaxy clustering5, 6 have thus been proposed as a powerful probe of the validity of GR on cosmological scales7, but despite substantial efforts8, 9, they suffer from systematic errors comparable to statistical uncertainties10 . Here, we present the results of a forward-modelling approach that fully exploits the sensitivity of the galaxy velocity field to modifications of GR. We use state-of-the-art high-resolutionN -body simulations of a standard GR (Λ cold dark matter (CDM)) model11 and a compellingf (R ) model12 —one of GR's simplest variants, in which the Ricci scalar curvature, R, in the Einstein–Hilbert action is replaced by an arbitrary function ofR —to build simulated catalogues of stellar-mass-selected galaxies through a robust match to the Sloan Digital Sky Survey13 . We find thatf (R ) fails to reproduce the observed redshift-space clustering on scales of ~1–10 Mpc h −1, whereh is the dimensionless Hubble parameter. Instead, the standardΛ CDM GR model agrees impressively well with the data. This result provides strong confirmation, on cosmological scales, of the robustness of Einstein's general theory of relativity. Predictions for the clustering of galaxies based on general relativity (GR) and on one of its more compelling variants are contrasted with observations. The former agree impressively well with the data, providing strong confirmation of GR on cosmological scales.