Related papers: Tracing the cosmic history by Gauss-Bonnet gravity
The methods of dynamical systems have found wide applications in cosmology, with focus either upon inflation or upon the passage into dark energy era. In this paper, we endeavor to capture the whole history of the universe into a dynamical…
We give a rigorous and mathematically clear presentation of the Covariant and Gauge Invariant theory of gravitational waves in a perturbed Friedmann-Lemaitre-Robertson-Walker universe for Fourth Order Gravity, where the matter is described…
We consider a brane world scenario in which the bulk action is assumed to have the form of a generic function of the Ricci scalar $f(\mathcal{R})$ and derive the resulting Einstein field equations on the brane. In a constant curvature bulk…
Flat space-time has not heretofore been thought a suitable locus in which to construct model universes because of the presumed necessity of incorporating gravitation in such models and because of the historical lack of a theory of…
In this thesis we will focus on Einstein's interpretation of gravity. We will examine how the most famous equations in cosmology are derived from GR and also some results of cosmological significance. We will see how combining that with…
The recently suggested generalized unimodular gravity theory, which was originally put forward as a model of dark energy, can serve as a model of cosmological inflation driven by the effective perfect fluid -- the dark purely gravitational…
We discuss solar system constraints on f(G) gravity models, where f is a function of the Gauss-Bonnet term G. We focus on cosmologically viable f(G) models that can be responsible for late-time cosmic acceleration. These models generally…
We suggest the modified gravity where some arbitrary function of Gauss-Bonnet (GB) term is added to Einstein action as gravitational dark energy. It is shown that such theory may pass solar system tests. It is demonstrated that modified GB…
Using techniques from singular perturbation theory, we explicitly calculate the cosmological evolution in a class of modified gravity models. By considering the (m)CDTT model, which aims to explain the current acceleration of the universe…
In this paper, we apply the holographic principle at the early universe, obtaining an inflation realization of holographic origin. First we show that under the consideration of extended infrared cut-offs, there exist a holographic…
We proposed the generalized holographic dark energy model where infrared cutoff is identified with the combination of the FRW universe parameters: the Hubble rate, particle and future horizons, cosmological constant, the universe life-time…
This review explores modified theories of gravity, particularly $f(R)$ gravity, as extensions to General Relativity (GR) that offer alternatives to dark energy for explaining cosmic acceleration. These models generalize the Einstein-Hilbert…
Accelerating cosmological models are constructed in a modified gravity theory dubbed as $f(R,T)$ gravity at the backdrop of an anisotropic Bianchi type-III universe. $f(R,T)$ is a function of the Ricci scalar $R$ and the trace $T$ of the…
The treatment of 1 + 3 covariant perturbation in a multifluid cosmology with the consideration of f (G) gravity, G being the Gauss-Bonnet term, is done in the present paper. We define a set of covariant and gauge-invariant variables to…
It is postulated that the action of the FRW-universe is the cosmological term of Einsteins theory (no curvature term - R0 Cosmology). The expansion equation emerging from the embedding of this most simple brane world with variable speed of…
We investigate the cosmological implications of $f(Q)$ gravity, which is a modified theory of gravity based on non-metricity, in non-flat geometry. We perform a detailed dynamical-system analysis keeping the $f(Q)$ function completely…
The geometric foundations of General Relativity are revisited, with particular attention to its gauge invariance, as a key to understanding the true nature of spacetime. Beyond the common image of spacetime as a deformable 'fabric' filling…
Horava and Melby-Thompson recently proposed a new version of the Horava-Lifshitz theory of gravity, in which the spin-0 graviton is eliminated by introducing a Newtonian pre-potential $\phi$ and a local U(1) gauge field $A$. In this paper,…
Some models of modified gravity and their observational manifestations are considered. It is shown, that gravitating systems with mass density rising with time evolve to a singular state with infinite curvature scalar. The universe…
The cosmology of general fourth order corrections to Einstein gravity is considered, both for a homogeneous and isotropic background and for general tensor perturbations. It is explicitly shown how the standard cosmological history can be…