Related papers: Phantom-Like Behavior in $f(R)$-Gravity
In this work, we reconstruct the $f(R)$ modified gravity for different ghost and generalized ghost dark energy models in FRW flat universe, which describe the accelerated expansion of the universe. The equation of state of reconstructed…
We propose a covariant ghost-free unimodular $F(R)$ gravity theory, which contains a three-form field and study its structure using the analogy of the proposed theory with a quantum system which describes a charged particle in uniform…
We review the equation of state for dark energy in modified gravity theories. In particular, we summarize the generic feature of the phantom divide crossing in the past and future in viable $f(R)$ gravity models.
The objective of the present paper is to study 4-dimensional weakly Ricci symmetric spacetimes $(WRS)_4$ with non-zero constant Ricci scalar. We prove that such a $(WRS)_4$ satisfying $F(R)$-gravity field equations represents a perfect…
Phantom energy can be visualized as a scalar field with a (non-canonical) negative kinetic energy term. We use the dynamical system formalism to study the attractor behavior of a cosmological model containing a phantom scalar field $\phi$…
Ghost-free non-local gravity is investigated with regards to its late-time dynamics. Viable solutions in this model are confronted with the observational data including the Pantheon+ catalogue of Type Ia supernovae, the Dark Energy…
We investigate quintessence and phantom dark energy scenarios, in which the scalar fields evolve in nearly flat potentials and are non-minimally coupled to gravity. We show that all such models converge to a common behavior and we provide…
We study the general chaotic features of dynamics of the phantom field modelled in terms of a single scalar field conformally coupled to gravity. We demonstrate that the dynamics of the FRW model with dark energy in the form of phantom…
In this work I show that a simple Field Theory on a non trivial gauge background may behave as a phantom field and contribute to an effective $w<-1$ state equation fluid contribution to cosmology.
We construct a Hamiltonian for the nonlocal F(R) theory in the present work. By this construction, we demonstrate the nature of the ghost degrees of freedom. Finally, we find conditions that give rise to ghost-free theories
This work is devoted to the study of analytic wormhole solutions within the framework of $f(R)$ gravity theory. To check the possibility of having wormhole structures satisfying energy conditions, by means of the class I approach the pair…
In the standard cosmological framework of the 0th-order FLRW metric and the use of perfect fluids in the stress-energy tensor, dark energy with an equation-of-state parameter $w < -1$ (known as phantom dark energy) implies negative kinetic…
We revisit the problem of phantom behaviour of effective dark energy in scalar-tensor gravity. The main focus is on the properties of the functions defining the model. We find that models with the present phantom behavior can be made…
We examine phantom dark energy models derived from a scalar field with a negative kinetic term for which V(phi) approaches infinity asymptotically. All such models can be divided into three classes, corresponding to an equation of state…
In this paper we consider FRW cosmology in $F(R,\phi)$ gravity. It is shown that in particular cases the bouncing behavior may appears in the model whereas the equation of state (EoS) parameter may crosses the phantom divider. For the…
We extend f(R) theories via the addition of a fundamental scalar field. The approach is reminiscent of the dilaton field of string theory and the Brans-Dicke model. f(R) theories attracted much attention recently in view of their potential…
We have investigated some bouncing cosmological models in an isotropic and homogeneous space time with the F(R) theory of gravity. Two functional forms of F(R) have been investigated with a bouncing scale factor. The dynamical parameters…
We show that f(R)-gravity can, in general, give rise to cosmological viable models compatible with a matter-dominated epoch evolving into a late accelerated phase. We discuss the various representations of f(R)-gravity as an ideal fluid or…
To explore possibilities of avoiding coincidence problem in $f(R)$ gravity we consider models in Einstein conformal frame which are equivalent to Einstein gravity with a minimally coupled scalar field. As the conformal factor determines the…
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…