http://arxiv.org/abs/1811.04445
We investigate the cosmological perturbations in the context of a Scalar-Tensor-Vector theory of Gravity known as MOG in the literature. At the weak field limit, MOG increases the strength of gravity, and consequently addresses some astrophysical tests, without invoking dark matter particles. Recent investigations show that MOG reproduces a background cosmological evolution similar to $\Lambda$CDM, but with a matter dominated phase different from the standard case. In fact, the expansion rate in the matter dominated epoch is higher in MOG compared to that of $\Lambda$CDM. In this paper, in order to further investigate whether MOG passes the cosmological observations, we study the evolution of linear matter perturbations and estimate the modified gravity parameters. Unlike some current claims in the relevant literature, we show that MOG reduces the growth rate of the perturbations. We then compare MOG to the redshift space distortion (RSD) data. We find that MOG yields a much higher value than $\Lambda$CDM for the power spectrum parameter $\sigma_8$. Although MOG cannot yet be ruled out by RSD data alone, the low growth and high $\sigma_8$ constitute a powerful challenge to the cosmological viability of MOG.
S. Jamali, M. Roshan and L. Amendola
Tue, 13 Nov 18
30/74
Comments: 22 pages, 6 figures and 1 table