Cosmological tests of modified gravity

By K. Koyama. Reports on progress in physics. Physical Society, 2015

626 citations recorded by the source corpus.

We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein’s theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard Λ ?>CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a813f9c3d1ba4865c456daaaf750775d792e8cda

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Citations in the corpus

The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: a tomographic measurement of cosmic structure growth and expansion rate based on optimal redshift weights (2018, background): “…Universe, these surveys are able to provide rich information on the past lightcone, which is crucial to unveil the physics of the cosmic acceleration (Riess et al. 1998; Perlmutter et al. 1999), through studies of dark energy (Weinberg et al. 2013) and gravity on cosmological scales (Koyama 2016).”
Horndeski theory and beyond: a review (2019, background): “We will not describe much about cosmological tests of gravity, which are covered by excellent reviews such as [15, 16, 17].”
Bouncing cosmology in f(Q) symmetric teleparallel gravity (2020, neutral): “[17] K.”
Accurate halo-model matter power spectra with dark energy, massive neutrinos and modified gravitational forces (2016, background): “Recent reviews of some of the menagerie of possible MG theories are given by Joyce et al. (2015) and Koyama (2016).”
Extended scalar-tensor theories of gravity (2016, neutral): “[3] for a review).”
Effective field theory of dark energy: A review (2019, background): “Usually one refers to these proposals as modified gravity (MG) theories [5, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30].”
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Constraining modified gravity (2016, background): “While it is clear that the acceleration mimics the cosmological constant in general effect, the exact physics is unclear, and both new energy-density components and modifications to GR, remain possibilities (Copeland et al. 2006; Koyama 2016).”