| Abstract: | Modified theories of Gravity (MoG) present a broad class of modifications of Einstein's GR with non-negligible effects at cosmological scales. This area has been a subject of intensive research in the past few years. The reason being that in MoG theories one can achieve the late-time bserved acceleration of the Universe avoiding the problems connected to the Cosmological Constant.
Most of the work focuses on either on theoretical studies or on potential MoG observational effects with respect to density field/clustering statistics. We discuss a potentially very powerful probe of MoG for cosmology. We show that the delicate MoG effects seen in the density field (both in configuration and the redshift space) are accompanied by a significantly larger effects in all the observables related to the peculiar velocity field of galaxies. We discuss the observables like velocity power spectrum, high-order hierarchical amplitudes, pairwise velocities, velocity dispersion and velocity correlation functions. We suggest that despite a much poorer quality of observational velocity data the overall gain in the strength of a MoG signal make the velocity field related observables a potential smoking gun for the modified gravity. |
