A concise description is presented in the basic features of formalism non-canonical spacetime volume forms and its application modified gravity theories cosmology. The well-known unimodular theory appears as a very special case. Concerning hot issues facing cosmology now, we specifically briefly outline construction of: (a) unified dark energy matter manifestations single material entity—a scal...

ABSTRACT In this paper, we quantify the ability of multiple measurements high-redshift quasars to constrain several theories modified gravity, including Dvali–Gabadadze–Porrati braneworld scenario, generalized Chaplygin gas, f(T) and polytropic Cardassian model. Recently released sample 1598 with X-ray ultraviolet flux in redshift range 0.036 ? z 5.1003, as well a compilation 120 intermediate-l...

Globular clusters (GCs) in the Milky Way have characteristic velocity dispersions that are consistent with the predictions of Newtonian gravity, and may be at odds with Modified Newtonian Dynamics (MOND) and possibly the cold dark matter model. We discuss a modified gravity (MOG) theory that can successfully model the velocity dispersions of GCs in the Galactic neighborhood. MOG produces veloci...

Any viable theory of modified Newtonian dynamics (MOND) as modified gravity is likely to require fields in addition to the usual tensor field of General Relativity. For such theories the MOND phenomenology emerges as an effective fifth force probably associated with a scalar field. Here I consider the constraints imposed upon such theories by solar system phenomenology, primarily by the absence...

Differences in masses inferred from dynamics, such as velocity dispersions or x rays, and those inferred from lensing are a generic prediction of modified gravity theories. Viable models, however, must include some nonlinear mechanism to restore general relativity (GR) in dense environments, which is necessary to pass Solar System constraints on precisely these deviations. In this paper, we stu...

The idea that the Einstein action should be modified by the addition of interactions involving higher powers of the Riemann curvature tensor has a long history stretching back to the early days of general relativity. Such higher curvature theories originally appeared in proposals by Weyl and Eddington for a geometric unification of electromagnetism and gravity[1]. Much later, interest arose in ...

Building on previous work, we explore the parameter space of general free functions in nonrelativistic modified gravity theories motivated by k-essence and other scalar-tensor theories. Using a few proposed tests, we aim to update Solar System based constraints on these ideas in line with previous theories and suggest their utility in constraining modification to GR, potentially even being able...