Theories of gravity are fundamentally a relation between matter and the geometric structure underlying spacetime. So once we put some additional restrictions on spacetime geometry, theory is bound to get impact, irrespective whether it general relativity or modified theories gravity. In present article, consider two curvature-based constraints, namely almost pseudo-Ricci symmetric weakly Ricci ...

We study the parametrized post-Newtonian (PPN) limit of higher-derivative-torsion Modified Teleparallel Gravity. start from covariant formulation modified Gravity by restoring spin connection theory. Then, we perform expansion tetrad field around Minkowski background and find perturbed equations. compute PPN metric for higher-order theories which allows us to show that at this more general clas...

A relativistic modified gravity (MOG) called Scalar-Tensor-Vector Gravity (STVG) desribes a self-consistent, stable gravity theory that contains Einstein’s general relativity in a well-defined limit. The theory has an extra degree of freedom, a vector field called a “phion” field whose curl is a skew symmetric field that couples to matter (“fifth force”). The spacetime geometry is described by ...

A theorem on higer-order derivative theories of gravity is proved. We find that the de Sitter/anti-de Sitter metric always a solution any generally covariant theory gravity. With this and general form entropy function for spacetimes, we show how to calculate spacetime in without knowing details modified metric. As an example, formula dS Lovelock obtained.

A recent study established a correspondence between the Generalized Uncertainty Principle (GUP) and Modified theories of gravity, particularly Stelle gravity. We investigate consequences this for inflation cosmological observables by evaluating power spectrum scalar tensor perturbations using two distinct methods. First, we employ PLANCK observations to determine GUP parameter γ0. Then, use val...

Modified gravity theories may provide an alternative to dark energy to explain cosmic acceleration. We argue that the observational programme developed to test dark energy needs to be augmented to capture new tests of gravity on astrophysical scales. Several distinct signatures of gravity theories exist outside the 'linear' regime, especially owing to the screening mechanism that operates insid...

Cooling processes of brown dwarf stars and giant planets are studied in the framework degenerate higher-order scalar-tensor theories. We confirm previous results field that effect modified gravity on substellar objects' age is pronounced most.

We derive universal properties of the near-horizon geometry spherically symmetric black holes that follow from observability a regular apparent horizon. Only two types solutions are admissible. After reviewing their we show only special form second type is consistent. describe how these results extend to modified theories gravity, including Einstein--Cartan theories. Then unique hole formation ...