14 research outputs found
Weyl geometry approach to describe planetary systems
In the present work we show that planetary mean distances can be calculated
through considering the Weyl geometry. We interpret the Weyl gauge field as a
vector field associated with the hypercharge of the particles and apply the
gauge concept of the Weyl geometry. The results obtained are shown to agree
with the observed orbits of all the planets and of the asteroid belt in the
solar system, with some empty states.Comment: 7 pages, no figure
Quintom dark energy in DGP braneworld cosmology
In this paper we consider a symmetrical 3-brane embedded in a
5-dimensional spacetime. We study the effective Einstein equation and
acceleration condition in presence of the quintom dark energy fluid as the bulk
matter field. It is shown that the time-dependent bulk quintom field induces a
time-dependent cosmological constant on the brane. In the framework of the DGP
model, the effective Einstein equation is obtained in two different cases: i)
where the quintom field is considered as the bulk matter field and the brane is
empty and, ii) where the quintom dark energy is confined on the brane and the
bulk is empty. We show that in both cases one could obtain a self-inflationary
solution at late time in positive branch , and an asymptotically
static universe in negative branch .Comment: 12 pages, 8 figure
Restoring New Agegraphic Dark Energy in RS II Braneworld
Motivated by recent works [1,2], we investigate new agegraphic model of dark
energy in the framework of RS II braneworld. We also include the case of
variable gravitational constant in our model. Furthermore, we establish
correspondence between the new agegraphic dark energy with other dark energy
candidates based on scalar fields.Comment: 13 pages, accepted for publication in IJT
CDM, DGP and extended phantom-like cosmologies
In this paper we compare outcomes of some extended phantom-like cosmologies
with each other and also with CDM\, and DGP. We focus on the
variation of the luminosity distances, the age of the universe and the
deceleration parameter versus the redshift in these scenarios. In a dynamical
system approach, we show that the accelerating phase of the universe in the
-DGP scenario is stable if one consider the \emph{curvature fluid} as a
phantom scalar field in the equivalent scalar-tensor theory, otherwise it is a
transient and unstable phenomenon. Up to the parameters values adopted in this
paper, the extended -DGP scenario is closer to the CDM
scenario than other proposed models. All of these scenarios explain the
late-time cosmic speed-up in their normal DGP branches, but the redshift at
which transition to the accelerating phase occurs are different: while the
DGP model transits to the accelerating phase much earlier, the
-DGP model transits to this phase much later than other scenarios.
Also, within the parameter spaces adopted in this paper, the age of the
universe in the -DGP model is larger than CDM, but this age in
-DGP is smaller than CDM.Comment: 37 pages, 6 figures, accepted for publication in Astrophyics and
Space Scienc