Einstein Spaces Modeling Nonminimal Modified Gravity

Abstract

Off-diagonal vacuum and nonvacuum configurations in Einstein gravity can mimic physical effects of modified gravitational theories of $f(R,T,R_{\mu \nu}T^{\mu \nu})$ type. To prove this statement, exact and approximate solutions are constructed in the review, which encode certain models of covariant Ho\v{r}ava type gravity with dynamical Lorentz symmetry breaking. The corresponding FLRW cosmological dynamics with possible nonholonomic deformations and the reconstruction procedure of certain actions closely related with the standard $\Lambda$CDM universe are studied. Off-diagonal generalizations of de Sitter universes are constructed which are generated through nonlinear gravitational polarization of fundamental physical constants and which model interactions with non-constant exotic fluids and effective matter. The problem of possible matter instability for such off-diagonal deformations in (modified) gravity theories is briefly discussed.Comment: latex 2e, 36 pages, this variant was accepted for publication to EPJP 130 (2015) 119 as an extended version (with two new sections and modified Introduction, Conclusion and Table of Reference) of a shorten variant article published by the same authors in Gen. Relativity Grav. 47 (2015) 64, arXiv: 1310.686