Related papers: Modified Einstein versus Modified Euler for Dark M…
We consider spatially covariant modified gravity in which the would-be scalar degree of freedom is made non-dynamical and hence there are just two tensorial degrees of freedom, i.e., the same number of dynamical degrees of freedom as in…
A generic prediction of the standard cosmology, based on general relativity (GR), dark matter and the cosmological constant (and more generally, smooth dark energy), is that, the two gravitational potentials describing the spatial and…
Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet.…
We analyze how to parametrize general modifications of the dark matter perturbations equations in a model-independent way. We prove that a general model with an imperfect and non-conserved dark matter fluid with bulk and shear viscosities…
One century after its formulation, Einstein's general relativity has made remarkable predictions and turned out to be compatible with all experimental tests. Most of these tests probe the theory in the weak-field regime, and there are…
We study the origin of fifth forces in scalar-tensor theories of gravity in the so-called Jordan frame, where the modifications to the gravitational sector are manifest. We focus on theories of Brans-Dicke type in which an additional scalar…
Cosmic growth of large scale structure probes the entire history of cosmic expansion and gravitational coupling. To get a clear picture of the effects of modification of gravity we consider a deviation in the coupling strength (effective…
Despite the success of general relativity (GR), the unexplained nature of dark energy on cosmological scales leaves open the question of whether GR provides a complete description of gravity. This quest is further motivated by growing…
Recently a new -quantum motivated- theory of gravity has been proposed that modifies the standard Newtonian potential at large distances when spherical symmetry is considered. Accordingly, Newtonian gravity is altered by adding an extra…
We investigate the dynamics of particles moving in a spacetime augmented by one extra dimension in the context of the induced matter theory of gravity. We examine the appearance of a fifth force as an effect caused by the extra dimension…
The current accelerated expansion of our universe could be due to an unknown energy component (dark energy) or a modification to general relativity (modified gravity). In the literature, it has been proposed that combining the probes of the…
In this paper we analyze a suite of cosmological simulations of modified gravitational action f(R) models, where cosmic acceleration is induced by a scalar field that acts as a fifth force on all forms of matter. In particular, we focus on…
A sizable fraction of the total energy density of the universe may be in heavy particles with a net dark $U(1)'$ charge comparable to its mass. When the charges have the same sign the cancellation between their gravitational and gauge…
General extensions of General Relativity (GR) based on bona fide degrees of freedom predict a fifth force which operates within massive objects, opening up an exciting opportunity to perform precision tests of gravity at stellar scales.…
Within the framework of the Projective Unified Field Theory the distribution of a dark matter gas around a central body is calculated. As a result the well-known formulas of the Newtonian gravitational interaction are altered. This dark…
This thesis is devoted to the study of gravitational theories which can be seen as modifications or generalisations of General Relativity. The motivation for considering such theories, stemming from Cosmology, High Energy Physics and…
We consider different observational effects to test modified gravity approach involving the cosmological constant in the common description of the dark matter and the dark energy. We obtain upper limits for the cosmological constant by…
The lack of detection of supersymmetric particles is leading to look at alternative avenues for explaining dark matter's effects. Among them, modified theories of gravity may play an important role accounting even for both dark components…
The standard cosmological model is based on general relativity and includes dark matter and dark energy. An important prediction of this model is a fixed relationship between the gravitational potentials responsible for gravitational…
The status of experimental tests of general relativity and of theoretical frameworks for analysing them is reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of special…