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Big-bang nucleosynthesis and cosmic microwave background constraints on nonminimally coupled theories of gravity

R. P. L. Azevedo, P. P. Avelino

Abstract
In this paper, we show that the baryon-to-photon ratio η is in general not conserved before decoupling in nonminimally coupled theories of gravity. We use big-bang nucleosynthesis and cosmic microwave background (CMB) limits on the baryon-to-photon ratio η to derive new constraints on modified gravity theories with a universal nonminimal coupling between matter and curvature, showing that they rule out a specific class of models previously considered in the literature as a substitute for the dark matter. We also compare these new constraints with the ones obtained from the COBE-FIRAS limits on CMB spectral distortions, highlighting the complementarity between them.

Keywords
General Relativity and Quantum Cosmology, Astrophysics - Cosmology and Nongalactic Astrophysics

Physical Review D
Volume 617, Issue 6, Page 6
2018 September

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia