We study dynamics of the equation of state parameter for a dark energy component non-minimally coupled to induced gravity on a warped DGP brane. We show that there are appropriate domains of the model parameters space that account for crossing of the phantom divide line. This crossing, which is possible for both branches of the scenario, depends explicitly on the values of the non-minimal coupling and warp factor. The effect of warp factor appears in the value of the redshift parameter at which phantom divide line crossing occurs.
Brane and warped Dvali-Gabadadze-Porrati inflationary universe models in the context of intermediate inflation are studied. In both models we consider that the energy density is a standard scalar field and we discuss the evolution of the universe during the slow-roll inflation. Also, we describe the conditions for these models. The corresponding Wilkinson Microwave Anisotropy Probe seven year data are utilized to fix some parameters in our models. Our results are compared to those found in General Relativity.
A warm inflationary universe scenario on a warped Dvali-Gabadadze-Porrati brane during intermediate inflation is studied. We consider a general form for the dissipative coefficient $Γ(T,ϕ)\propto T^{m}/ϕ^{m-1}$, and also study this model in the weak and strong dissipative regimes. We analyze the evolution of the universe in the slow-roll approximation, and find the exact solutions to the equations of motion. In both regimes, we utilize recent data from the BICEP2 experiment and also from the Planck satellite to constrain the parameters in our model in accordance with the theory of cosmological…
We consider the non-minimally kinetic coupled version of DGP brane model, where the kinetic term of the scalar field is coupled to the metric and Einstein tensor on the brane by a coupling constant $ζ$. We obtain the corresponding field equations, using the Friedmann-Robertson-Walker metric and the perfect fluid, and study the inflationary scenario to confront the numerical analysis of six typical scalar field potentials with the current observational results. We find that among the suggested potentials and coupling constants, subject to the e-folding $N=60$, the potentials $V(ϕ)=σϕ$, $V(ϕ)=σϕ…
We study possible crossing of the phantom divide line in a DGP-inspired $F(R,ϕ)$ braneworld scenario where scalar field and curvature quintessence are treated in a unified framework. With some specific form of $F(R,ϕ)$ and by adopting a suitable ansatz, we show that there are appropriate regions of the parameters space which account for late-time acceleration and admit crossing of the phantom divide line.
We construct a warm inflation model with inflaton field non-minimally coupled to induced gravity on a warped DGP brane. We incorporate possible modification of the induced gravity on the brane in the spirit of $f(R)$-gravity. We study cosmological perturbations in this setup. In the case of two field inflation such as warm inflation, usually entropy perturbations are generated. While it is expected that in the case of one field inflation these perturbations to be removed, we show that even in the absence of the radiation field, entropy perturbations are generated in our setup due to non-minima…
We study the static, analytical solution of black holes in the warped DGP braneworld scenario. We show that the linearized field equations and matching conditions lead to solutions that are not compatible with Schwarzschild-(A)dS$_{(4)}$ solutions on the brane. This incompatibility is similar to vDVZ discontinuity in massive gravity theory. Following the standard procedure to remove this discontinuity, which firstly was proposed by Vainshtein, we keep some appropriate nonlinear terms in the field equations. This strategy has its origin in the fact that the spatial extrinsic curvature of the br…
We investigate observational constraints on the normal branch of the warped DGP braneworld cosmology by using observational data from Type Ia Supernovae (SNIa), Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and Baryon Gas Mass Fraction of cluster of galaxies. The best fit values of model free parameters are: $Ω_m=0.240^{+0.050}_{-0.130}$ and $Ω_{r_c}=0.000^{+0.014}$ at $1σ$ confidence interval by using Gold sample SNIa+CMB shift parameter+BAO+Gas mass fraction of baryons in cluster of galaxies. The results for essence sample SNIa combined with CMB shift parameter, BAO a…
An impressed feature of inflation on warped Dvali-Gabadadze-Porrati (DGP) brane is that the inflationary phase exits spontaneously for a scalar inflaton field with exponential potential, which presents a graceful exit mechanism for the inflation. But its reheating mechanism leaves open. We investigate the curvaton reheating in inflation on warped DGP brane model. The reheating may occur in effctively 5 dimensional or 4 dimensional stage. We study the permitted parameter space of the curvaton field in detail. We demonstrate how the inflation model of the warped DGP brane is improved by the curv…
We propose a phantom crossing Dvali--Gabadadze--Porrati (DGP) model. In our model, the effective equation of state of the DGP gravity crosses the phantom divide line. We demonstrate crossing of the phantom divide does not occur within the framework of the original DGP model or the DGP model developed by Dvali and Turner. By extending their model, we construct a model that realizes crossing of the phantom divide. DGP models can account for late-time acceleration of the universe without dark energy. Phantom Crossing DGP model is more compatible with recent observational data from Type Ia Superno…
We study the observational constraints on the Phantom Crossing DGP model. We demonstrate that the crossing of the phantom divide does not occur within the framework of the original Dvali-Gabadadze-Porrati (DGP) model or the DGP model developed by Dvali and Turner. By extending their model in the framework of an extra dimension scenario, we study a model that realizes crossing of the phantom divide. We investigate the cosmological constraints obtained from the recent observational data of Type Ia Supernovae, Cosmic Microwave Background anisotropies, and Baryon Acoustic Oscillations. The best fi…
In this paper we first obtain Friedmann equations for the $(n-1)$-dimensional brane embedded in the $(n+1)$-dimensional bulk, with intrinsic curvature term of the brane included in the action (DGP model). Then, we show that one can always rewrite the Friedmann equations in the form of the first law of thermodynamics, $dE=TdS+WdV$, at apparent horizon on the brane, regardless of whether there is the intrinsic curvature term on the brane or a cosmological constant in the bulk. Using the first law, we extract the entropy expression of the apparent horizon on the brane. We also show that in the ca…
Braneworld models with induced gravity have the potential to replace dark energy as the explanation for the current accelerating expansion of the Universe. The original model of Dvali, Gabadadze and Porrati (DGP) demonstrated the existence of a ``self--accelerating'' branch of background solutions, but suffered from the presence of ghosts. We present a new large class of braneworld models which generalize the DGP model. Our models have negative curvature in the bulk, allow a second brane, and have general brane tensions and localized curvature terms. We exhibit three different kinds of ghosts,…
We propose a phantom crossing Dvali--Gabadadze--Porrati (DGP) model. In our model, the effective equation of state of the DGP gravity crosses the phantom divide line. We demonstrate crossing of the phantom divide does not occur within the framework of the original DGP model or the DGP model developed by Dvali and Turner. By extending their model, we construct a model that realizes crossing of the phantom divide. We find that the smaller the value of the new introduced parameter $β$ is, the older epoch crossing of the phantom divide occurs in. Our model can account for late-time acceleration of…
Warm inflationary universe models on a warped Dvali-Gabadadze-Porrati brane are studied. General conditions required for these models to be realizable are derived and discussed. By using an effective exponential potential we develop models for constant and variable dissipation coefficient ratio $r=\fracΓ{3 H}$. We use recent astronomical observations for constraining the parameters appearing in our models.
It has been shown recently that phantom-like effect can be realized on the normal branch of the DGP setup without introduction of any phantom matter neither in the bulk nor on the brane and therefore without violation of the null energy condition. It has been shown also that inclusion of the Gauss-Bonnet term in the bulk action modifies this picture via curvature effects. Here, based on the Lue-Starkman conjecture on the dynamical screening of the brane cosmological constant in the DGP setup, we extend this proposal to a general DGP-inspired $f(R,ϕ)$ model that stringy effects in the ultra-vio…
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. We study with details the effects of the non-minimal coupling and dissipation on the inflationary dynamics on the normal DGP branch of this 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 observa…
We discuss an inflation model, in which the inflation is driven by a single scalar field with exponential potential on a warped DGP brane. In contrast to the power law inflation in standard model, we find that the inflationary phase can exit spontaneously without any mechanism. The running of the index of scalar perturbation spectrum can take an enough large value to match the observation data, while other parameters are in a reasonable region.
It is demonstrated that the claim in the paper "Crossing $ω=-1$ by a single scalar field on a Dvali-Gabadadze-Porrati brane" by H Zhang and Z-H Zhu [Phys.Rev.D75,023510(2007)], about a prove that there do not exist scaling solutions in a universe with dust in a Dvali-Gabadadze-Porrati (DGP) braneworld scenario, is incorrect.
We have studied a DGP-inspired braneworld scenario where the idea of Lorentz invariance violation has been combined into a specifying preferred frame that embed a dynamical normal vector field to brane. We propose the Lorentz violating DGP brane models with enough parameters can explain crossing of phantom divide line. Also we have considered the model for proper cosmological evolution that is according to the observed behavior of the equation of state. In other view point, we have described a Rip singularity solution of model that occur in this model.
We study the particle trajectories in the recently proposed five dimensional warped (generalized) Ellis-Bronnikov spacetime (5D-WGEB) (which does not require exotic matter) as well as it's four dimensional counterpart (4D-GEB) in detail and conduct a comparative study. Analytical approach provides conditions which determines three types of trajectories (trapped, returning and crossing) for both 4D and 5D spacetimes. Notably in 5D geometry existence of trapped trajectories become highly sensitive to the initial conditions. We have solved the timelike geodesic equations numerically and presented…
Massachusetts Institute of Technology（麻省理工学院）；Institute for Advanced Study（高等研究院）；Princeton University（普林斯顿大学）；Harvard University（哈佛大学）；New York University（纽约大学）
We study cosmological inflation on a warped DGP braneworld where inflaton field is non-minimally coupled to induced gravity on the brane. We present a detailed calculation of the perturbations and inflation parameters both in Jordan and Einstein frame. We analyze the parameters space of the model fully to justify about the viability of the model in confrontation with recent observational data. We compare the results obtained in these two frames also in order to judge which frame gives more acceptable results in comparison with observational data.
