15 research outputs found
The Coincidence Problem in Holographic f(R) Gravity
It is well-known that gravity models formulated in Einstein conformal
frame are equivalent to Einstein gravity together with a minimally coupled
scalar field. In this case, the scalar field couples with the matter sector and
the coupling term is given by the conformal factor. We apply the holographic
principle to such interacting models. In a spatially flat universe, we show
that the Einstein frame representation of models leads to a constant
ratio of energy densities of dark matter to dark energy.Comment: 10 pages, no figure
Reconstructing f(R) model from Holographic DE: Using the observational evidence
We investigate the corresponding relation between gravity and an
interacting holographic dark energy. By obtaining conditions needed for some
observational evidence such as, positive acceleration expansion of universe,
crossing the phantom divide line and validity of thermodynamics second law in
an interacting HDE model and corresponding it with mode of gravity we
find a viable model which can explain the present universe. We also
obtain the explicit evolutionary forms of the corresponding scalar field,
potential and scale factor of universe.Comment: 11page. phys. Scr (2012
Holographic Dark Energy Like in Gravity
We investigate the corresponding relation between gravity and
holographic dark energy. We introduce a kind of energy density from
which has role of the same as holographic dark energy.
We obtain the differential equation that specify the evolution of the
introduced energy density parameter based on varying gravitational constant. We
find out a relation for the equation of state parameter to low redshifts which
containing varying correction.Comment: 10 page
Modified gravity in a viscous and non-isotropic background
We study the dynamical evolution of an model of gravity in a viscous
and anisotropic background which is given by a Bianchi type-I model of the
Universe. We find viable forms of gravity in which one is exactly the
Einsteinian model of gravity with a cosmological constant and other two are
power law models. We show that these two power law models are stable
with a suitable choice of parameters. We also examine three potentials which
exhibit the potential effect of models in the context of scalar tensor
theory. By solving different aspects of the model and finding the physical
quantities in the Jordan frame, we show that the equation of state parameter
satisfy the dominant energy condition. At last we show that the two power law
models behave like quintessence model at late times and also the shear
coefficient viscosity tends to zero at late times.Comment: 7 pages, 2 figure