We follow a number of recent authors, who have considered additional contributions to the gravitational potential in the form of Yukawa-like terms ( White & Kochanek 2001 Peebles 2002 Sealfon et al. In the present paper, we will concentrate on this last aspect. Finally, large galaxy surveys have been analysed looking for signatures in the power spectrum due to deviations from the inverse-square law ( Sealfon, Verde & Jimenez 2005 Shirata et al. Recently, proposals have been made to extend these theories to a general covariant framework ( Bekenstein 2004) and evolution of perturbations in this theory has been considered ( Skordis et al. The implications of MOND on large-scale structure in a Friedmann–Lemaître–Robertson–Walker (FLRW) universe were discussed in Nusser (2002). Constraints on Newton's constant from the primordial abundances of light elements were discussed by Umezu, Kiyotomo & Masanobu (2005). Such radical modifications of gravitational physics may seem difficult to test, but our ability to make precise observations of cosmological dynamics on scales of ≳10 h −1 Mpc is now good enough to permit detailed tests of gravity theories even on these scales.Įxamples of such work include White & Kochanek (2001), who determined constraints on the long-range properties of gravity from weak gravitational lensing cosmic shear. On one hand, MOND proposals make gravity stronger on scales of galaxies to explain flat rotation curves without dark matter ( Milgrom 1983 Sanders 1998), on the other hand, alternative theories aim to find a mechanism for cosmic acceleration without dark energy, as a result of gravity leaking into higher dimensions on scales comparable to the horizon ( Dvali, Gabadadze & Porrati 2000). The body of evidence is quite impressive, considering the enormous extrapolation from the empirical basis, but the gravitational inverse-square law and its relativistic generalization are supported by high-precision tests from measurements in the laboratory, the Solar system and the binary pulsar only up to scales of ≲10 13 cm ( Aldelberger, Heckel & Nelson 2003).ĭespite the overall success of general relativity, non-standard theories have received much recent attention, largely motivated by finding alternative explanations for the ‘dark’ sector of the Universe. General relativity has passed many important tests up to the length- and time-scales of the observable Universe ( Peebles 2002, 2004). Gravitation, cosmology: theory, dark matter, large-scale structure of Universe 1 INTRODUCTION Back-reaction on density growth from a modified cosmic expansion rate should, however, also affect the normalization of the power spectrum, with a shape distortion similar to the case of a non-modified background. This phenomenon is almost perfectly degenerate in power-spectrum shape with the effect of a background of massive neutrinos. Enhancement of gravity affects the subsequent evolution, boosting large-scale power in a way that resembles the effect of a lower matter density. The coupling between baryons and cold dark matter across recombination is negligibly affected by modified gravity physics if the proper cut-off length of the long-range Yukawa-like force is ≳10 h −1 Mpc. Evolution of perturbations is considered in general non-flat cosmological models with a cosmological constant, and an analytical approximation for the growth function is provided. We model such deviations as a Yukawa-like contribution to the gravitational potential and discuss the growth function in a mixed dark matter model with adiabatic initial conditions. Deviations from the gravitational inverse-square law would imprint scale-dependent features on the power spectrum of mass density fluctuations.
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