Constraints on decaying early modified gravity from cosmological observations

2016/03/31 by Nelson A. Lima, Vanessa Smer-Barreto, Lucas Lombriser
Earth and Planetary Sciences · Physics and Astronomy · #Anisotropy #Astrophysics #Classical mechanics #Cosmic microwave background #Cosmology #Cosmology and Gravitation Theories #Dark energy #Decoupling (probability) #Galaxy #Geometry #Geophysics and Gravity Measurements #Gravitation #Mathematical physics #Physics #Planck #Quantum mechanics #Redshift #Scalar (mathematics) #Scalar field #Solar and Space Plasma Dynamics #Theoretical physics #astro-ph.CO #gr-qc

paper · pdf · doi:10.1103/physrevd.94.083507

published as Phys. Rev. D 94, 083507 (2016) · 13 pages, 5 figures and 1 table. Version 2 matches manuscript accepted by PRD

arxiv created 2016/09/16 · openalex publication_date 2016/10/04 · arxiv updated 2016/10/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Most of the information on our cosmos stems from either late-time observations or the imprint of early-time inhomogeneities on the cosmic microwave background. We explore to what extent early modifications of gravity, which become significant after recombination but then decay toward the present, can be constrained by current cosmological observations. For the evolution of the gravitational modification, we adopt the decaying mode of a hybrid metric-Palatini f(R) gravity model which is designed to reproduce the standard cosmological background expansion history and due to the decay of the modification is naturally compatible with Solar System tests. We embed the model in the effective field theory description of Horndeski scalar-tensor gravity with an early-time decoupling of the gravitational modification. Since the quasistatic approximation for the perturbations in the model breaks down at high redshifts, where modifications remain relevant, we introduce a computationally efficient correction to describe the evolution of the scalar field fluctuation in this regime. We compare the decaying early-time modification against geometric probes and recent Planck measurements and find no evidence for such effects in the observations. Current data constrains the scalar field value at |f_R(z=z_on)|\ensuremath\lesssim10^\ensuremath-2 for modifications introduced at redshifts z_on\ensuremath∼(500--1000) with the present-day value |f_R0|\ensuremath\lesssim10^\ensuremath-8. Finally, we comment on constraints that will be achievable with future 21-cm surveys and gravitational wave experiments.

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