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1.
Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar R, one uses the torsion scalar T for the Lagrangian density. Recently teleparallel dark energy has been proposed by Geng et al. (in Phys. Lett. B 704, 384, 2011). They have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the Lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly. 相似文献
2.
We discuss the expansion of the universe in the FRLW model assuming that the source of dark energy is either tachyonic scalar field or quintessence. The tachyonic scalar field with exponential and power-law potential (function of homogeneous scalar field ?) both gives exponential expansion of the universe. It is found that this behaviour is not distinguishable from the quintessence with respect to these potentials. 相似文献
3.
In this paper it is shown that in non-minimally coupled Brans-Dicke theory containing a self-interacting potential, a suitable conformal transformation can automatically give rise to an interaction between the normal matter and the Brans-Dicke scalar field. Considering the scalar field in the Einstein frame as the quintessence matter, it has been shown that such a non-minimal coupling between the matter and the scalar field can give rise to a late time accelerated expansion for the universe preceded by a decelerated expansion for very high values of the Brans-Dicke parameter ω. We have also studied the observational constraints on the model parameters considering the Hubble and Supernova data. 相似文献
4.
We consider generalized teleparallel gravity in the flat FRW universe with a viable power-law f(T) model. We construct its equation of state and deceleration parameters which give accelerated expansion of the universe in quintessence era for the obtained scale factor. Further, we develop correspondence of f(T) model with scalar field models such as, quintessence, tachyon, K-essence and dilaton. The dynamics of scalar field as well as scalar potential of these models indicate the expansion of the universe with acceleration in the f(T) gravity scenario. 相似文献
5.
O. Sergijenko Yu. Kulinich B. Novosyadlyj V. Pelykh 《Kinematics and Physics of Celestial Bodies》2009,25(1):17-27
The evolution of scalar perturbations is studied for 2-component (non-relativistic matter and dark energy) cosmological models
at the linear and non-linear stages. The dark energy is assumed to be the scalar field with either classical or tachyonic
Lagrangian and constant equation-of-state parameter w. The fields and potentials were reconstructed for the set of cosmological parameters derived from observations. The comparison
of the calculated within these models and observational large-scale structure characteristics is made. It is shown that for
w = const such analysis can’t remove the existing degeneracy of the dark energy models.
The article is published in the original. 相似文献
6.
We consider Brans-Dicke theory with a self-interacting potential in Einstein conformal frame. We introduce a class of solutions
in which an accelerating expansion is possible in a spatially flat universe for positive and large values of the Brans-Dicke
parameter consistent with local gravity experiments. In this Einstein frame formulation, the theory appears as an interacting
quintessence model in which the interaction term is given by the conformal transformation. In such an interacting model, we
shall show that the solutions lead simultaneously to a constant ratio of energy densities of matter and the scalar field. 相似文献
7.
We explore the prospects for using future supernova observations to probe the dark energy. We focus on quintessence, an evolving scalar field that has been suggested as a candidate for the dark energy. After simulating the observations that would be expected from the proposed SuperNova / Acceleration Probe satellite ( SNAP ), we investigate two methods for extracting information concerning quintessence from such data. First, by expanding the quintessence equation of state as w Q ( z ) = w Q (0) −α ln(1 + z ) , to fit the data, it is possible to reconstruct the quintessence potential for a wide range of smoothly varying potentials. Secondly, it will be possible to test the basic properties of the dark energy by constraining the parameters Ω Q , w Q and α. We show that it may be possible, for example, to distinguish between quintessence and the cosmological constant in this way. Furthermore, when supernova data are combined with other planned cosmological observations, the precision of reconstructions and parameter constraints is significantly improved, allowing a wider range of dark energy models to be distinguished. 相似文献
8.
K. Saaidi H. Sheikhahmadi T. Golanbari S. W. Rabiei 《Astrophysics and Space Science》2013,348(1):233-240
We study the holographic dark energy (HDE) model in generalized Brans-Dicke scenario with a non-minimal coupling between the scalar field and matter Lagrangian namely Chameleon Brans Dicke (CBD) mechanism. In this study we consider the interacting and non-interacting cases for two different cutoffs. The physical quantities of the model such as, equation of state (EoS) parameter, deceleration parameter and the evolution equation of dimensionless parameter of dark energy are obtained. We shall show that this model can describe the dynamical evolution of fraction parameter of dark energy in all epochs. Also we find the EoS parameter can cross the phantom divide line by suitable choices of parameters without any mines kinetic energy term. 相似文献
9.
Antonio Pasqua A. Khodam-Mohammadi Mubasher Jamil R. Myrzakulov 《Astrophysics and Space Science》2012,340(1):199-208
Motivated by the holographic principle, it has been suggested that the dark energy density may be inversely proportional to the area A of the event horizon of the universe. However, such a model would have a causality problem. In this work, we consider the entropy-corrected version of the holographic dark energy model in the non-flat FRW universe and we propose to replace the future event horizon area with the inverse of the Ricci scalar curvature. We obtain the equation of state (EoS) parameter ω Λ, the deceleration parameter q and WD￠\Omega_{D}' in the presence of interaction between Dark Energy (DE) and Dark Matter (DM). Moreover, we reconstruct the potential and the dynamics of the tachyon, K-essence, dilaton and quintessence scalar field models according to the evolutionary behavior of the interacting entropy-corrected holographic dark energy model. 相似文献
10.
In this paper, we solve the Einstein’s field equations for the space-time described by a special plane symmetric metric with
dark energy, and the exact solutions which offer an alternative and complementary approach to study cosmological models are
obtained. The dark energy is given by either the quintessence or the modified Chaplygin gas. We show the models are isotropic
and analyze the expansion scalar and the deceleration parameter of the models. 相似文献
11.
Tachyonic scalar field-driven late universe with dust matter content is considered. The cosmic expansion is modeled with power-law and phantom power-law expansion at late time, i.e. z?0.45. WMAP7 and its combined data are used to constraint the model. The forms of potential and the field solution are different for quintessence and tachyonic cases. Power-law cosmology model (driven by either quintessence or tachyonic field) predicts unmatched equation of state parameter to the observational value, hence the power-law model is excluded for both quintessence and tachyonic field. In the opposite, the phantom power-law model predicts agreeing valued of equation of state parameter with the observational data for both quintessence and tachyonic cases, i.e. $w_{\phi, 0} = -1.49^{+11.64}_{-4.08}$ (WMAP7+BAO+H 0) and $w_{\phi, 0} = -1.51^{+3.89}_{-6.72} $ (WMAP7). The phantom-power law exponent β must be less than about ?6, so that the ?2<w ?,0<?1. The phantom power-law tachyonic potential is reconstructed. We found that dimensionless potential slope variable Γ at present is about 1.5. The tachyonic potential reduced to V=V 0 ? ?2 in the limit Ω m,0→0. 相似文献
12.
We investigate the evolution of matter density perturbations and some properties of the peculiar velocity field for a special class of exponential potentials in a scalar field model for quintessence, for which a general exact solution is known. The data from the 2-degree Field Galaxy Redshift Survey (2dFGRS) suggest a value of the present-day pressureless matter density ΩM0 = 0.18 ± 0.05 . 相似文献
13.
We consider a cosmological model in which a scalar field is non-minimally coupled to scalar torsion and a vector field through two coupling functions in the framework of teleparallel gravity. The explicit forms of the coupling functions and the scalar field potential are explored, under the assumption that the Lagrangian admits the Noether symmetry in the Friedmann–Lemaître–Robertson–Walker (FLRW) space–time. The existence of such symmetry allows to solve the equations of motion and achieve exact solutions of the scale factor, scalar and vector fields. It is found that the vector field contributes significantly in the accelerating expansion of the universe in the early times, while the scalar field plays an essential role in the late times. 相似文献
14.
This paper investigates the validity of generalized second law of thermodynamics using both the power law and logarithmic entropy corrected formulas in a general scalar-tensor gravity. For this purpose, we take non-flat FRW universe model filled with magnetized perfect fluid matter bounded by four different horizons namely Hubble, apparent, particle and event horizons. We introduce a non-minimal interaction between scalar and matter fields and take Lagrangian density of non-linear electromagnetic effects. Finally, we extend this study to anisotropic case by taking Bianchi I universe model bounded by apparent horizon only and investigate the role of anisotropy parameter on the validity of GSLT. In this case, we also explore the behavior of some cosmological parameters. 相似文献
15.
We propose in this paper an interacting holographic dark energy (IHDE) model in chameleon–tachyon cosmology by interaction
between the components of the dark sectors. In the formalism, the interaction term emerges from the scalar field coupling
matter Lagrangian in the model rather than being inserted into the formalism as an external source for the interaction. The
correspondence between the tachyon field and the holographic dark energy (HDE) densities allows to reconstruct the tachyon
scalar field and its potential in a flat FRW universe. The model can show the accelerated expansion of the universe and satisfies
the observational data. 相似文献
16.
Adnan Aslam Mubasher Jamil Davood Momeni Ratbay Myrzakulov Muneer Ahmad Rashid Muhammad Raza 《Astrophysics and Space Science》2013,348(2):533-540
In literature usual point like symmetries of the Lagrangian have been introduced to study the symmetries and the structure of the fields. This kind of Noether symmetry is a subclass of a more general family of symmetries, called Noether gauge symmetries (NGS). Motivated by this mathematical tool, in this paper, we study the generalized Noether symmetry of quintom model of dark energy, which is a two component fluid model with quintessence and phantom scalar fields. Our model is a generalization of the Noether symmetries of a single and multiple components which have been investigated in detail before. We found the general form of the quintom potential in which the whole dynamical system has a point like symmetry. We investigated different possible solutions of the system for diverse family of gauge function. Specially, we discovered two family of potentials, one corresponds to a free quintessence (phantom) and the second is in the form of quadratic interaction between two components. These two families of potential functions are proposed from the symmetry point of view, but in the quintom models they are used as phenomenological models without clear mathematical justification. From integrability point of view, we found two forms of the scale factor: one is power law and second is de-Sitter. Some cosmological implications of the solutions have been investigated. 相似文献
17.
We consider a spatially homogeneous and isotropic flat Robertson-Walker model filled with a scalar (or tachyonic) field minimally
coupled to gravity in the framework of higher derivative theory. We discuss the possibility of the emergent universe with
normal and phantom scalar fields (or normal and phantom tachynoic fields) in higher derivative theory. We find the exact solution
of field equations in normal and phantom scalar fields and observe that the emergent universe is not possible in normal scalar
field as the kinetic term is negative. However, the emergent universe exists in phantom scalar field in which the model has
no time-like singularity at infinite past. The model evolves into an inflationary stage and finally admits an accelerating
phase at late time. The equation of state parameter is found to be less than −1 in early time and tends to −1 in late time
of the evolution. The scalar potential increases from zero at infinite past to a flat potential in late time. More precisely,
we discuss the particular case for phantom field in detail. We also carry out a similar analysis in case of normal and phantom
tachyonic field and observe that only phantom tachyonic field solution represents an emergent universe. We find that the coupling
parameter of higher order correction affects the evolution of the emergent universe. The stability of solutions and their
physical behaviors are discussed in detail. 相似文献
18.
We study the late-time cosmological viability of the solutions in the DGP braneworld scenario. We consider a quintessence field trapped on the normal branch of the DGP model and we suppose this scalar field is both minimally and non-minimally coupled to induced gravity on the brane. Since a successful cosmological model should therefore admit for a sequence of epochs: a radiation era, a sufficiently long matter dominated era and a final stable positively accelerated scaling solution, we analyze the cosmological properties of system in its critical points. 相似文献
19.
Tame Gonzalez Rolando Cardenas Israel Quiros Yoelsy Leyva 《Astrophysics and Space Science》2007,310(1-2):13-18
In this work we investigate the evolution of matter (linear) density perturbations for quintessence models with a self-interaction
potential that is a combination of exponentials. One of the models is based on the Einstein theory of gravity, while the other
is based on the Brans-Dicke scalar tensor theory. We constrained the parameter space of the models by using the determinations
of the growth rate of perturbations derived from data of the 2-degree Field Galaxy Redshift Survey.
相似文献
20.
We examine the possibility that a substantial fraction of the total energy density in a spatially flat Universe is composed
of a time-dependent and spatially inhomogeneous component whose equation-of-state differs from that of baryons, neutrinos,
dark matter, or radiation. In this lecture, we report on our investigations of the case in which the additional energy component,
dubbed "quintessence", is due to a dynamical scalar field evolving in a potential. We have computed the effects on the background
cosmological evolution, the cosmic microwave background (CMB) and mass power spectrum, finding a broad range of cosmologically
viable models. We stress three important features of the quintessence or Q-component: the time evolution of the equation-of-state;
the length-scale dependence of the speed of propagation of the fluctuations in the Q-component; and, the contribution of quintessence
fluctuations to the CMB anisotropy spectrum.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献