Searching for Hints of Modified Gravity in Cosmological and Sub-mm Force Data

Experimental and/or observational signals indicating possible violation of General Relativity can in principle emerge on various scales starting from submm scales up to cosmological Gpc scales. Such signals include new forces on sub-mm scales that generalize the Newtonian force as well as the growth of cosmological perturbations on Mpc/Gpc scales that may indicate a redshift dependence of Newton’s constant. I review recent work searching for such signals in cosmological growth rate $f\sigma 8$ data (RSD measurements) and in laboratory torsion balance data (Washington experiment). These studies indicate the presence of signals that are inconsistent with GR at $2\sigma$ level or more. These signals may be due either to systematics in the analyzed data, or to large statistical fluctuations in the data or they may be early hints for violation of General Relativity. Focusing on the later possibility, I also briefly discuss specific theoretical models that may be consistent with these signals. Such models include infinite derivative (non-local) gravity and scalar tensor theories.

A large part of the talk is based on the following recent papers:
https://arxiv.org/pdf/1703.10538.pdf (Phys.Rev. D96 (2017) no.2, 023542),
https://arxiv.org/pdf/1611.07293.pdf (Phys.Rev. D95 (2017) no.8, 084050)
and https://arxiv.org/pdf/1803.01337.pdf