共查询到20条相似文献，搜索用时 437 毫秒
1.
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
2.
We consider the cosmological dynamics of a tachyon field localized on the extended DGP braneworld scenario. We present a detailed analysis of the critical points in the phase space of the model, their stability and late-time cosmological viability of the solutions. We study the luminosity distance behavior of this ?EDGP model and compare it with ΛCDM model. Also we show that the EDGP solutions in the presence of tachyon field can explain late time acceleration of the universe. 相似文献
3.
We study the effects of the non-minimal coupling on the dissipative dynamics of the warm inflation in a braneworld setup,
where the inflaton field is non-minimally coupled to induced gravity on the warped DGP brane. A warped DGP scenario is a hybrid
model containing both DGP and RSII character. We study with details the effects of the non-minimal coupling and dissipation
on the inflationary dynamics on the normal DGP branch of this hybrid scenario in the high-dissipation and high-energy regime. We show that incorporation of the non-minimal coupling
in this setup decreases the number of e-folds relative to the minimal case. We also compare our model parameters with recent
observational data. 相似文献
4.
Malihe Heydari-Fard 《Astrophysics and Space Science》2010,325(2):287-292
Using the effective gravitational field equations in the warped DGP brane-world scenario (Maeda et al. in Phys. Rev. D 68:024033,
2003), we study spherically symmetric vacuum (static black hole) solutions on the brane. Working with a conformally flat bulk,
we have obtained an exact Schwarzschild–de Sitter black hole solution similar to the standard solution in the presence of
a cosmological constant, which confirms the idea that an extra term in the effective vacuum field equations on the warped
DGP brane can play the role of a positive cosmological constant. 相似文献
5.
We reconsider the issue of cosmological dynamics in a DGP setup with a bulk scalar field. The ghost-free, normal branch of
this DGP-inspired braneworld scenario has the potential to realize a self-consistent phantom-like behavior. The roles played
by the bulk canonical scalar field on this phantom-like dynamics are explored. Within a dynamical system approach, the effective
phantom nature of the scenario is investigated with details. This analysis shows that there is a stable, late-time de Sitter
phase. 相似文献
6.
We consider cosmological dynamics of a canonical bulk scalar field, which is coupled non-minimally to 5-dimensional Ricci scalar in a DGP setup. We show that presence of this non-minimally coupled bulk scalar field affects the jump conditions of the original DGP model significantly. Within a superpotential approach, we perform some numerical analysis of the model parameter space and consider bulk-brane energy exchange in this setup. Also we show that the normal, ghost-free branch of the DGP solutions in this case has the potential to realize a self-consistent phantom-like behavior and therefore explains late time acceleration of the universe in a consistent way. 相似文献
7.
The recently released Planck data have constrained 4-dimensional inflationary parameters even more accurately than ever. We consider an extension of the braneworld model with induced gravity and a non-minimally coupled scalar field on the brane. We constraint the inflation parameters in this setup, by adopting six types of potential, in confrontation with the joint Planck + WMAP9 + BAO data. We show that a potential of the type V(φ)=V 0exp(?βφ) has the best fit with newly released observational data. 相似文献
8.
A proposal to study the original and new agegraphic dark energy in DGP braneworld cosmology is presented in this work. To verify our model with the observational data, the model is constrained by a variety of independent measurements such as Hubble parameter, cosmic microwave background anisotropies, and baryon acoustic oscillation peaks. The best fitting procedure shows the effectiveness of agegraphic parameter n in distinguishing between the original and new agegraphic dark energy scenarios and subsequent cosmological findings. In particular, the result shows that in both scenarios, our universe enters an agegraphic dark energy dominated phase. 相似文献
9.
We study the structure of electromagnetic field of slowly rotating magnetized star in a Randall-Sundrum II type braneworld.
The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and frozen-in dipolar
magnetic field. Maxwell’s equations for the external magnetic field of the star in the braneworld are analytically solved
in approximation of small distance from the surface of the star. We have also found numerical solution for the electric field
outside the rotating magnetized neutron star in the braneworld in dependence on brane tension. The influence of brane tension
on the electromagnetic energy losses of the rotating magnetized star is underlined. Obtained “brane” corrections are shown
to be relevant and have non-negligible values. In comparison with astrophysical observations on pulsars spindown data they
may provide an evidence for the brane tension and, thus, serve as a test for the braneworld model of the Universe. 相似文献
10.
We report results on the construction of cosmological braneworld models in the context of the Einstein-Gauss-Bonnet gravity,
which include the leading correction to the Einstein-Hilbert action suggested by superstring theory. We obtain and study the
equations governing the dynamics of the standard cosmological models. We find that they can be written in the same form as
in the case of the Randall-Sundrum model but with time-varying four-dimensional gravitational and cosmological constants.
Finally, we discuss the cosmological evolution predicted by these models and their compatibility with observational data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
This paper deals with the study of dynamical or phase space analysis of Bianchi I universe in Brans-Dicke gravity with chameleon scalar field. For this purpose, the matter contents are taken to be perfect fluid with magnetic field effects described by the non-linear Maxwell Lagrangian density. By taking some ansatz for the field potential and the interaction function in chameleon cosmology, we discuss three cases: Bianchi I universe with perfect fluid, FRW universe with magnetized perfect fluid and Bianchi I universe with magnetized perfect fluid. In all cases, we calculate fixed or critical points and discuss stability of the respective configuration for radiation as well as matter dominated eras. We also evaluate some cosmological parameters in each case for matter dominated era only and investigate their cosmological implications. 相似文献
12.
Artyom V. Astashenok Artyom V. Yurov Sergey V. Chervon Evgeniy V. Shabanov Mohammad Sami 《Astrophysics and Space Science》2014,353(2):319-328
We develop a method for constructing exact cosmological solutions in brane world cosmology. New classes of cosmological solutions on Randall–Sandrum brane are obtained. The superpotential and Hubble parameter are represented in quadratures. These solutions have inflationary phases under general assumptions and also describe an exit from the inflationary phase without a fine tuning of the parameters. Another class solutions can describe the current phase of accelerated expansion with or without possible exit from it. 相似文献
13.
Dagoberto Escobar Carlos R. Fadragas Genly Leon Yoelsy Leyva 《Astrophysics and Space Science》2014,349(1):575-602
In this work we present a phase space analysis of a quintessence field and a perfect fluid trapped in a Randall-Sundrum’s Braneworld of type 2. We consider a homogeneous but anisotropic Bianchi I brane geometry. Moreover, we consider the effect of the projection of the five-dimensional Weyl tensor onto the three-brane in the form of a negative Dark Radiation term. For the treatment of the potential we use the “Method of f-devisers” that allows investigating arbitrary potentials in a phase space. We present general conditions on the potential in order to obtain the stability of standard 4D and non-standard 5D de Sitter solutions, and we provide the stability conditions for both scalar field-matter scaling solutions, scalar field-dark radiation solutions and scalar field-dominated solutions. We find that the shear-dominated solutions are unstable (particularly, contracting shear-dominated solutions are of saddle type). As a main difference with our previous work, the traditionally ever-expanding models could potentially re-collapse due to the negativity of the dark radiation. Additionally, our system admits a large class of static solutions that are of saddle type. These kinds of solutions are important at intermediate stages in the evolution of the universe, since they allow the transition from contracting to expanding models and viceversa. New features of our scenario are the existence of a bounce and a turnaround, which lead to cyclic behavior, that are not allowed in Bianchi I branes with positive dark radiation term. Finally, as specific examples we consider the potentials V∝sinh?α (β?) and V∝[cosh(ξ?)?1] which have simple f-devisers. 相似文献
14.
《New Astronomy》2017
We studied Bianchi type-V space-time using magnetic domain wall in f(R, T) theory of gravity and deciphered the exact solutions of the corresponding field equations. In this study, we discussed the physical behavior of the resultant cosmological model in the presence and absence of magnetic field with the help of few physical parameters. 相似文献
15.
P. H. R. S. Moraes 《Astrophysics and Space Science》2014,352(1):273-279
It is well known that the universe is undergoing a phase of accelerated expansion. Plenty of models have already been created with the purpose of describing what causes this non-expected cosmic feature. Among them, one could quote the extradimensional and the f(R,T) gravity models. In this work, in the scope of unifying Kaluza-Klein extradimensional model with f(R,T) gravity, cosmological solutions for density and pressure of the universe are obtained from the induced matter model application. Particular solutions for vacuum quantum energy and radiation are also shown. 相似文献
16.
V. S. Morozova B. J. Ahmedov A. A. Abdujabbarov A. I. Mamadjanov 《Astrophysics and Space Science》2010,330(2):257-266
Plasma magnetosphere surrounding rotating magnetized neutron star in the braneworld has been studied. For the simplicity of calculations Goldreich-Julian charge density is analyzed for the aligned neutron star with zero inclination between magnetic field and rotation axis. From the system of Maxwell equations in spacetime of slowly rotating star in braneworld, second-order differential equation for electrostatic potential is derived. Analytical solution of this equation indicates the general relativistic modification of an accelerating electric field and charge density along the open field lines by brane tension. The implication of this effect to the magnetospheric energy loss problem is underlined. It was found that for initially zero potential and field on the surface of a neutron star, the amplitude of the plasma mode created by Goldreich-Julian charge density will increase in the presence of the negative brane charge. Finally we derive the equations of motion of test particles in magnetosphere of slowly rotating star in the braneworld. Then we analyze particle motion in the polar cap and show that brane tension can significantly change conditions for particle acceleration in the polar cap region of the neutron star. 相似文献
17.
Capture cross section of magnetized particle (with nonzero magnetic moment) by braneworld black hole in uniform magnetic field
is studied. The magnetic moment of particle was chosen as it was done by de Felice and Sorge (Class. Quantum Gravity 20:469,
2003) and for the simplicity particle with zero electric charge is chosen. It is shown that the spin of particle as well as the
brane parameter are to sustain the stability of particles circularly orbiting around the black hole in braneworld i.e. spin
of particles and brane parameter try to prevent the capture by black hole. 相似文献
18.
In this paper, we study an anisotropic Bianchi-I space-time model in f(R) theory of gravity in the presence of perfect fluid as a matter contains. The aim of this paper is to find the functional form of f(R) from the field equations and hence the solution of various cosmological parameters. We assume that the deceleration parameter to be a constant, and the shear scalar proportional to the expansion scalar to obtain the power-law form of the scale factors. We find that the model describes the decelerated phases of the universe under the choice of certain constraints on the parameters. The model does not show the acceleration expansion and also transition from past deceleration to present accelerating epoch. We discuss the stability of the functional form of f(R) and find that it is completely stable for describing the decelerating phase of the universe. 相似文献
19.
In this work, we first obtain the hydrostatic equilibrium equation in dilaton gravity. Then, we examine some of the structural characteristics of a strange quark star in dilaton gravity in the context of Einstein gravity. We show that the variations of dilaton parameter do not affect the maximum mass, but variations in the cosmological constant lead to changes in the structural characteristics of the quark star. We investigate the stability of strange quark stars by applying the MIT bag model with dilaton gravity. We also provide limiting values for the dilaton field parameter and cosmological constant. We also study the effects of dilaton gravity on the other properties of a quark star such as the mean density and gravitational redshift.We conclude that the last reported value for the cosmological constant does not affect the maximum mass of a strange quark star. 相似文献
20.
J. A. Belinchón 《Astrophysics and Space Science》2013,345(2):387-397
We study how may behave the gravitational and the cosmological “constants”, (G and Λ) in several scalar-tensor theories with Bianchi II symmetries. By working under the hypothesis of self-similarity we find exact solutions for three different theoretical models, which are: the Jordan-Brans-Dicke (JBD) with Λ(?), the usual JBD model with potential U(?) (that mimics the behavior of Λ(?)) and the induced gravity (IG) model proposed by Sakharov and Zee. After a careful study of the obtained solutions we may conclude that the solutions are quite similar although the IG model shows some peculiarities. 相似文献