378 research outputs found
Bulk Filling Branes and the Baryon Density in AdS/QCD with gravity back-reaction
We consider the gravity back reaction on the metric due to the baryon density
in effective ads/qcd model by reconsidering the role of the charged AdS black
hole. Previously it has been known that the U(1) charge is dual to the
R-charge. Here we point out that if we consider the case where is
completely filled with flavor branes, the gravity back reaction produces
charged AdS black hole where the effect of charge on the metric is proportional
to . As a consequence, phase diagram changes qualitatively if we allow
finite: it closes at the finite density unlike the probe brane
embedding approach.
Another issue we discuss here is the question whether there is any chemical
potential dependence in the confining phase. We consider this problem in the
hard wall model with baryon charge. We conclude that there is a non-trivial
dependence on the chemical potential in this case also.Comment: 17 pages 3x2 figures, v2: references added;v3 published version,
title change and reference adde
A New Type of Dark Energy Model
In this paper, we propose a general form of the equation of state (EoS) which
is the function of the fractional dark energy density . At least,
five related models, the cosmological constant model, the holographic dark
energy model, the agegraphic dark energy model, the modified holographic dark
energy model and the Ricci scalar holographic dark energy model are included in
this form. Furthermore, if we consider proper interactions, the interactive
variants of those models can be included as well. The phase-space analysis
shows that the scaling solutions may exist both in the non-interacting and
interacting cases. And the stability analysis of the system could give out the
attractor solution which could alleviate the coincidence problem.Comment: Minor modifications, references adde
New Agegraphic Dark Energy in Gravity
In this paper we study cosmological application of new agegraphic dark energy
density in the gravity framework. We employ the new agegraphic model of
dark energy to obtain the equation of state for the new agegraphic energy
density in spatially flat universe. Our calculation show, taking , it is
possible to have crossing -1. This implies that one can
generate phantom-like equation of state from a new agegraphic dark energy model
in flat universe in the modified gravity cosmology framework. Also we develop a
reconstruction scheme for the modified gravity with action.Comment: 8 pages, no figur
Probing interaction and spatial curvature in the holographic dark energy model
In this paper we place observational constraints on the interaction and
spatial curvature in the holographic dark energy model. We consider three kinds
of phenomenological interactions between holographic dark energy and matter,
i.e., the interaction term is proportional to the energy densities of dark
energy (), matter (), and matter plus dark energy
(). For probing the interaction and spatial curvature in
the holographic dark energy model, we use the latest observational data
including the type Ia supernovae (SNIa) Constitution data, the shift parameter
of the cosmic microwave background (CMB) given by the five-year Wilkinson
Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic
oscillation (BAO) measurement from the Sloan Digital Sky Survey (SDSS). Our
results show that the interaction and spatial curvature in the holographic dark
energy model are both rather small. Besides, it is interesting to find that
there exists significant degeneracy between the phenomenological interaction
and the spatial curvature in the holographic dark energy model.Comment: 11 pages, 5 figures; to appear in JCA
Interacting Agegraphic Dark Energy
A new dark energy model, named "agegraphic dark energy", has been proposed
recently, based on the so-called K\'{a}rolyh\'{a}zy uncertainty relation, which
arises from quantum mechanics together with general relativity. In this note,
we extend the original agegraphic dark energy model by including the
interaction between agegraphic dark energy and pressureless (dark) matter. In
the interacting agegraphic dark energy model, there are many interesting
features different from the original agegraphic dark energy model and
holographic dark energy model. The similarity and difference between agegraphic
dark energy and holographic dark energy are also discussed.Comment: 10 pages, 5 figures, revtex4; v2: references added; v3: accepted by
Eur. Phys. J. C; v4: published versio
Interacting new agegraphic Phantom model of dark energy in non-flat universe
In this paper we consider the new agegraphic model of interacting dark energy
in non-flat universe. We show that the interacting agegraphic dark energy can
be described by a phantom scalar field. Then we show this phantomic description
of the agegraphic dark energy and reconstruct the potential of the phantom
scalar field.Comment: 8 pages, no figur
Interacting New Agegraphic Dark Energy in a Cyclic Universe
The main goal of this work is investigation of NADE in the cyclic universe
scenario. Since, cyclic universe is explained by a phantom phase (),
it is shown when there is no interaction between matter and dark energy, ADE
and NADE do not produce a phantom phase, then can not describe cyclic universe.
Therefore, we study interacting models of ADE and NADE in the modified
Friedmann equation. We find out that, in the high energy regime, which it is a
necessary part of cyclic universe evolution, only NADE can describe this
phantom phase era for cyclic universe. Considering deceleration parameter tells
us that the universe has a deceleration phase after an acceleration phase, and
NADE is able to produce a cyclic universe. Also it is found valuable to study
generalized second law of thermodynamics. Since the loop quantum correction is
taken account in high energy regime, it may not be suitable to use standard
treatment of thermodynamics, so we turn our attention to the result of
\citep{29}, which the authors have studied thermodynamics in loop quantum
gravity, and we show that which condition can satisfy generalized second law of
thermodynamics.Comment: 8 pages, 3 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
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
Interacting entropy-corrected new agegraphic dark energy in Brans-Dicke cosmology
Motivated by a recent work of one of us [1], we extend it by using quantum
(or entropy) corrected new agegraphic dark energy in the Brans-Dicke cosmology.
The correction terms are motivated from the loop quantum gravity which is one
of the competitive theories of quantum gravity. Taking the non-flat background
spacetime along with the conformal age of the universe as the length scale, we
derive the dynamical equation of state of dark energy and the deceleration
parameter. An important consequence of this study is the phantom divide
scenario with entropy-corrected new agegraphic dark energy. Moreover, we assume
a system of dark matter, radiation and dark energy, while the later interacts
only with dark matter. We obtain some essential expressions related with dark
energy dynamics. The cosmic coincidence problem is also resolved in our model.Comment: 16 pages, no figure, accepted for publication in Gen. Relativ. Gra
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