At the present state-of-the-art, the simplest inflationary models, based either on scalar fields in General Relativity or on modified f(R) gravity, which produce the best fit to all existing observational data, require only one dimensionless parameter taken from observations. These models include the pioneer $R+R^2$ one [1], the Higgs model, and the mixed $R^2$-Higgs model that has been shown...
Observations of bright near the Galactic Center give an opportunity to test GR predictions but also to constrain alternative gravity parameters, in particular, to limit graviton mass for the case of massive gravity theories.
Due to an expected progress of observational facilities Zakharov et al. (2005a) proposed to use global and ground – space VLBI observations in mm band to detect a...
