207 research outputs found
Singularly Perturbed Markov Chains with Two Small Parameters: A Matched Asymptotic Expansion
AbstractThis work is concerned with asymptotic properties of solutions to forward equations for singularly perturbed Markov chains with two small parameters. It is motivated by the model of a cost-minimizing firm involving production planning and capacity expansion and a two-level hierarchical decomposition. Our effort focuses on obtaining asymptotic expansions of the solutions to the forward equation. Different from previous work on singularly perturbed Markov chains, the inner expansion terms are constructed by solving certain partial differential equations. The methods of undetermined coefficients are used. The error bound is obtained
Effects of multiple heavy metal contamination and repeated phytoextraction by Sedum plumbizincicola on soil microbial properties
Scalar-Tensor Theory of Gravity and Generalized Second Law of Thermodynamics on the Event Horizon
In blackhole physics, the second law of thermodynamics is generally valid
whether the blackhole is a static or a non-static one. Considering the universe
as a thermodynamical system the second law of blackhole dynamics extends to the
non-negativity of the sum of the entropy of the matter and the horizon, known
as generalized second law of thermodynamics(GSLT). Here, we have assumed the
universe to be bounded by the event-horizon or filled with perfect fluid and
holographic dark energy in two cases. Thus considering entropy to be an
arbitrary function of the area of the event-horizon, we have tried to find the
conditions and the restrictions over the scalar field and equation of state for
the validity of the GSLT and both in quintessence-era and in phantom-era in
scalar tensor theory.Comment: 8 page
Holographic dark energy with time varying parameter
We consider the holographic dark energy model in which the model parameter
evolves slowly with time. First we calculate the evolution of EoS
parameter as well as the deceleration parameter in this generalized version of
holographic dark energy (GHDE). Depending on the parameter , the phantom
regime can be achieved earlier or later compare with original version of
holographic dark energy. The evolution of energy density of GHDE model is
investigated in terms of parameter . We also show that the time-dependency
of can effect on the transition epoch from decelerated phase to
accelerated expansion. Finally, we perform the statefinder diagnostic for GHDE
model and show that the evolutionary trajectories of the model in plane
are strongly depend on the parameter .Comment: 16 pages, 4 figures, accepted by Astrophys Space Sc
Validity of the Generalized Second Law of Thermodynamics of the Universe Bounded by the Event Horizon in Holographic Dark Energy Model
In this letter, we investigate the validity of the generalized second law of
thermodynamics of the universe bounded by the event horizon in the holographic
dark energy model. The universe is chosen to be homogeneous and isotropic and
the validity of the first law has been assumed here. The matter in the universe
is taken in the form of non-interacting two fluid system- one component is the
holographic dark energy model and the other component is in the form of dust.Comment: 8 page
Diagnostic for Dilaton Dark Energy
diagnostic can differentiate between different models of dark energy
without the accurate current value of matter density. We apply this geometric
diagnostic to dilaton dark energy(DDE) model and differentiate DDE model from
LCDM. We also investigate the influence of coupled parameter on the
evolutive behavior of with respect to redshift . According to the
numerical result of , we get the current value of equation of state
=-0.952 which fits the WMAP5+BAO+SN very well.Comment: 6 pages and 6 figures
Holographic dark energy in a non-flat universe with Granda-Oliveros cut-off
Motivated by Granda and Oliveros (GO) model, we generalize their work to the
non-flat case. We obtain the evolution of the dark energy density, the
deceleration and the equation of state parameters for the holographic dark
energy model in a non-flat universe with GO cut-off. In the limiting case of a
flat universe, i.e. , all results given in GO model are obtained.Comment: 11 pages, 5 figure
Reconstructing interacting new agegraphic polytropic gas model in non-flat FRW universe
We study the correspondence between the interacting new agegraphic dark
energy and the polytropic gas model of dark energy in the non-flat FRW
universe. This correspondence allows to reconstruct the potential and the
dynamics for the scalar field of the polytropic model, which describe
accelerated expansion of the universe.Comment: 9 page
Power-law entropy-corrected HDE and NADE in Brans-Dicke cosmology
Considering the power-law corrections to the black hole entropy, which appear
in dealing with the entanglement of quantum fields inside and outside the
horizon, the holographic energy density is modified accordingly. In this paper
we study the power-law entropy-corrected holographic dark energy in the
framework of Brans-Dicke theory. We investigate the cosmological implications
of this model in detail. We also perform the study for the new agegraphic dark
energy model and calculate some relevant cosmological parameters and their
evolution. {As a result we find that this model can provide the present cosmic
acceleration and even the equation of state parameter of this model can cross
the phantom line provided the model parameters are chosen suitably}.Comment: 14 pages, 2 figure, accepted by IJT
Holographic \Lambda(t)CDM model in a non-flat universe
The holographic CDM model in a non-flat universe is studied in
this paper. In this model, to keep the form of the stress-energy of the vacuum
required by general covariance, the holographic vacuum is enforced to exchange
energy with dark matter. It is demonstrated that for the holographic model the
best choice for the IR cutoff of the effective quantum field theory is the
event horizon size of the universe. We derive the evolution equations of the
holographic CDM model in a non-flat universe. We constrain the
model by using the current observational data, including the 557 Union2 type Ia
supernovae data, the cosmic microwave background anisotropy data from the 7-yr
WMAP, and the baryon acoustic oscillation data from the SDSS. Our fit results
show that the holographic CDM model tends to favor a spatially
closed universe (the best-fit value of is -0.042), and the 95%
confidence level range for the spatial curvature is .
We show that the interaction between the holographic vacuum and dark matter
induces an energy flow of which the direction is first from vacuum to dark
matter and then from dark matter to vacuum. Thus, the holographic
CDM model is just a time-varying vacuum energy scenario in which
the interaction between vacuum and dark matter changes sign during the
expansion of the universe.Comment: 8 pages, 4 figures. version for publication in EPJC. arXiv admin
note: text overlap with arXiv:1112.235
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