Related papers: Modified gravity with disappearing cosmological co…
One of the so-called viable modified gravities is analyzed. This kind of gravity theories are characterized by a well behavior at local scales, where General Relativity is recovered, while the modified terms become important at the…
We present a class of modified-gravity theories which we call ultra-local models. We add a scalar field, with negligible kinetic terms, to the Einstein-Hilbert action. We also introduce a conformal coupling to matter. This gives rise to a…
We investigate the modified $F(R)$ gravity theory with the function $F(R) = (1-\sqrt{1-2\lambda R-\sigma (\lambda R)^2})/\lambda$. The action is converted into Einstein$-$Hilbert action at small values of $\lambda$ and $\sigma$. The local…
We investigate the impact on cosmological observables of $f(Q)$-gravity, a specific class of modified gravity models in which gravity is described by the non-metricity scalar, $Q$. In particular we focus on a specific model which is…
The discovery of the accelerated expansion of the universe highlighted General Relativity's inability to naturally account for dark energy without invoking a finely tuned cosmological constant. In response, a wide range of alternative…
We consider f(R) modified gravity theories in the metric variation formalism and attempt to reconstruct the function f(R) by demanding a background LCDM cosmology. In particular we impose the following requirements: a. A background cosmic…
Modified gravity has attracted much attention over the last few years and remains a potential candidate for dark energy. In particular, the so-called viable f(R) gravity theories, which are able to both recover General Relativity (GR) and…
We carry out a suite of cosmological simulations of modified action f(R) models where cosmic acceleration arises from an alteration of gravity instead of dark energy. These models introduce an extra scalar degree of freedom which enhances…
We investigate the cosmological and the local tests of the f(R) theory of modified gravity via the observations of (1) the cosmic expansion and (2) the cosmic structures and via (3) the solar-system experiments. To fit the possible cosmic…
Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution was standard $\Lambda$CDM in the past and that the present matter density and power spectrum normalization are the same as in a $\Lambda$CDM…
In the context of f(R) theories of gravity, we study the cosmological evolution of scalar perturbations by using a completely general procedure. We find that the exact fourth-order differential equation for the matter density perturbations…
In this work, we analyse the late-time evolution of the universe for a particular $f(R)$ gravity model built from an exponential function of the scalar curvature. Following the literature, we write the field equations in terms of a suited…
We propose a new model of f(R) gravity containing Arctan function in the lagrangian. We show here that this model satisfies fifth force constraint unlike a similar model in Kruglov 2013. In addition to this, we carry out the fixed point…
Models of modified gravity offer promising alternatives to the concordance $\Lambda$CDM cosmology to explain the late-time acceleration of the universe. A popular such model is $f(R)$ gravity, in which the Ricci scalar in the…
The orbital Lense-Thirring precession is considered in the context of constraints for weak-field General Relativity involving the cosmological constant $\Lambda$. It is shown that according to the current accuracy of satellite measurements…
In this work we present a few simple cosmological models under the modified theory of gravity in the particular form of $f(R,\mathcal{T})=R+2f(\mathcal{T})$, where $R$ is the Ricci Scalar and $\mathcal{T}$ is the trace of the…
We propose a model for modified gravity that meets the conditions of viability. The model has stable constant curvature solution and for an special case contains flat space time solution. The model also leads to matter stability under small…
We consider some cosmological aspects of nonlocal modified gravity with $\Lambda$ term, where nonlocality is of the type $R \mathcal{F}(\Box) R$. Using ansatz of the form $\Box R = r R +s,$ we find a few a(t) nonsingular bounce cosmological…
We study cosmological evolution in a flat FLRW spacetime in the context of modified STEGR gravity or $f(Q)$, using an exponential two-parameter model which represents a smooth perturbative expansion around the $\Lambda$CDM model. The…
Alternative cosmological models have been under deep scrutiny in recent years, aiming to address the main shortcomings of the $\Lambda$CDM model. Moreover, as the accuracy of cosmological surveys improved, new tensions have risen between…