There has been increasing interest in investigating the possible parity violating features gravity theory and on cosmological scales. In this work, we consider a class of scalar-nonmetricity theory, which Lagrangian is polynomial built nonmetricity tensor scalar field. The coupled with field through its first order derivative. Besides monomials that are quadratic tensor, also construct cubic bo...

It has been proposed that cosmic acceleration or inflation can be driven by replacing the EinsteinHilbert action of general relativity with a function f(R) of the Ricci scalar R. Such f(R) gravity theories have been shown to be equivalent to scalar-tensor theories of gravity that are incompatible with Solar System tests of general relativity, as long as the scalar field propagates over Solar Sy...

Scalar fields with inverse power-law effective potentials may provide a negative pressure component to the energy density of the universe today, as required by cosmological observations. In order to be cosmologically relevant today, the scalar field should have a mass mφ = O(10 −33eV), thus potentially inducing sizable violations of the equivalence principle and space-time variations of the cou...

The analysis of certain singularities in scalar-tensor gravity contained in a recent paper is completed, and situations are pointed out in which these singularities cannot occur. Recently, Abramo et al. [1] have investigated certain geometric singularities occurring in the gravitational sector of scalar-tensor theories described by the action

We consider a quantum scalar field on the classical background of an asymptotically anti--de Sitter black hole and backreaction field's stress-energy tensor induces geometry. The is computed by solving reduced-order semiclassical Einstein equations sourced simple analytical approximations for renormalized expectation value tensor. When massless conformally coupled, we adopt Page's approximation...

Quantum uctuations in the background geometry of a black hole are shown to aaect the propagation of matter states falling into the black hole in a foliation that corresponds to observations purely outside the horizon. A state that starts as a Minkowski vacuum at past null innnity gets entangled with the gravity sector, so that close to the horizon it can be represented by a statistical ensemble...

Abstract: We derive the gravitational equations of motion of general theories of gravity from thermodynamics applied to a local Rindler horizon through any point in spacetime. Specifically, for a given theory of gravity, we substitute the corresponding Wald entropy into the Clausius relation. Our approach works for all diffeomorphism-invariant theories of gravity in which the Lagrangian is a po...

Following some ideas in the Landau’s book, some corrections about errors in the old literature on scalar gravitational waves are given and discussed. Even if such errors can be considered not important from the point of view of observations, because they do not alter the interferometric response function for scalar gravitational waves, the presented analysis is due and very important for a sake...

We investigate a linearized tensor-tensor theory of gravity with torsion and a perturbed torsion wave solution is discovered in background Minkowski spacetime with zero torsion. Furthermore, gauge transformations of any perturbed tensor field are derived in general background non-Riemannian geometries. By calculating autoparallel deviations, both longitudinal and transverse polarizations of the...

Within the context of modified gravity and dark energy scenarios of the accelerated universe, we study the stability of de Sitter space with respect to inhomogeneous perturbations using a gauge– independent formalism. In modified gravity the stability condition is exactly the same that one obtains from a homogeneous perturbation analysis, while the stability condition in scalar–tensor gravity i...