Related papers: Cosmic Acceleration and Modified Gravitational Mod…
We construct the covariant nonlocal action for recently suggested long-distance modifications of gravity theory motivated by the cosmological constant and cosmological acceleration problems. This construction is based on the special…
Cosmological acceleration is difficult to accommodate in theories of fundamental interactions involving supergravity and superstrings. An alternative is that the acceleration is not universal but happens in a large localized region, which…
We show how to construct consistent braneworld models which exhibit late time acceleration. Unlike self-acceleration, which has a de Sitter vacuum state, our models have the standard Minkowski vacuum and accelerate only in the presence of…
Several models within the framework of Einstein-Gauss-Bonnet gravities are considered with regard their late-time phenomenological viability. The models contain a non-minimally coupled scalar field and satisfy a constraint on the scalar…
In this paper, we investigate the late-time cosmic acceleration in mimetic $f(R,T)$ gravity with Lagrange multiplier and potential in a Universe containing, besides radiation and dark energy, a self-interacting (collisional) matter. We…
An explicitly covariant formulation is presented of a modified DGP scenario proposed recently [1], to avoid the instability of the self-accelerating branch. It is based on the introduction of a bulk scalar field with appropriate non-minimal…
In recent times, there has been an increasing interest with theories of modified gravity as a means to gain a deeper understanding of the universe's late-time acceleration phase. In this study we focused our attention on a specific…
We analyse the cosmological evolution of a generalised axion-like field that drives the late-time acceleration of the Universe. This model can exhibit tracking behaviour, which alleviates the coincidence problem. The cosmological…
We consider a scenario of modified gravity, which is generic to late-time acceleration, namely, acceleration in the Jordan frame and no acceleration in the Einstein frame. The possibility is realized by assuming an interaction between dark…
Recently, new arguments (astro-ph/0501152, hep-th/0503117) for how corrections from super-Hubble modes can explain the present-day acceleration of the universe have appeared in the literature. However, in this letter, we argue that, to…
Modifications to gravity that add additional functions of the Ricci curvature to the Einstein-Hilbert action -- collectively known as $f(R)$ theories -- have been studied in great detail. When considered as complete theories of gravity they…
Einstein-Gauss-Bonnet (EGB) model is recently restudied in order to analyze new consequences in gravitation, modifying appropriately the Einstein-Hilbert action. The consequences in EGB cosmology are mainly geometric, with higher order…
Cosmologically motivated theories that explain small acceleration rate of the Universe via modification of gravity at very large, horizon or super-horizon distances, can be tested by precision gravitational measurements at much shorter…
The recent discovery of a ghost-free, non-linear extension of the Fierz-Pauli theory of massive gravity, and its bigravity formulation, introduced new possibilities of interpreting cosmological observations, in particular, the apparent…
With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realized. We show that a confirmation of equality to the speed of…
It is generally argued that the present cosmological observations support the accelerating models of the universe, as driven by the cosmological constant or `dark energy'. We argue here that an alternative model of the universe is possible…
Conditions for accelerated expansion of Friedmann-Robertson-Walker space-time are analyzed. Connection of this scenario with present-day observations are reviewed. It is explained how a scalar field could be responsible for cosmic…
We have studied the evolution of the Universe in the generalized Einstein action of the form $R+\beta R^2$, where $R$ is the scalar curvature and $\beta=\rm const.$. We have found exact cosmological solutions that predict the present cosmic…
We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired…
The current standard cosmological model is constructed within the framework of general relativity with a cosmological constant $\Lambda$, which is often associated with dark energy, and phenomenologically explains the accelerated cosmic…