Narrow Results

A proposal to study the effect of interaction in an agegraphic dark energy model in DGP brane-world cosmology is presented in this paper. After explaining the details, we proceed to apply the dynamical system approach to the model to analyze its stability. We first constrain model parameters with a variety of independent observational data such as cosmic microwave background anisotropies, baryon acoustic oscillation peaks and observational Hubble data. Then, we obtain the critical points related to different cosmological epochs. In particular, we conclude that in the presence of interaction, dark energy dominated era could be a stable point if model parameters n and $\beta$, obey a given constraint. Also, big rip singularity is avoidable in this model.

Evolution of the density parameter in the anisotropic DGP braneworld model is studied. The role of shear and cross-over scale in the evolution of Ω_ρ is examined for both the branches of solution in the DGP model. The evolution is modified significantly compared to the FRW model and further it does not depend on the value of γ alone. Behavior of the cosmological density parameter Ω_ρ is unaltered in the late universe. The study of decceleration parameter shows that the entry of the universe into self-accelerating phase is determined by the value of shear. We also obtain an estimate of the shear parameter , which is in agreement with the constraints obtained in the literature using data.

In this paper, we consider a normal branch of the DGP cosmological model with a quintessence scalar field on the brane as the dark energy component. Using the dynamical system approach, we study the stability properties of the model. We find that $\lambda$, as one of our new dimensionless variables which is defined in terms of the quintessence potential, has a crucial role in the history of the universe. We divide our discussion into two parts: a constant $\lambda$ and a varying $\lambda$. In the case of a constant $\lambda ,$ we calculate all the critical points of the model even those at infinity and then assume all of them as instantaneous critical points in the varying $\lambda$ situation which is the main part of this paper. We find that the effect of the extra dimension in such a model is independent of the value of $\lambda$. Then, we consider a Gaussian potential for which $\lambda$ is not constant but varies from zero to infinity. We discuss the evolution of the dynamical variables of the model and conclude that their asymptotic behaviors follow the trajectories of the moving critical points. Also, we find two different possible fates for the universe. In one of them, it could experience an accelerated expansion, but then enters a decelerating phase and finally reaches a stable matter-dominated solution. In the other scenario, the universe could approach the matter-dominated critical point without experiencing any accelerated expansion. We argue that the first scenario is more compatible with observations.

This paper deals with the study of the effect of Maxwell’s nonlinear electrodynamics (NLED) in the framework of Dvali–Gabadadze–Porrati (DGP) brane gravity for Friedmann–Robertson–Walker (FRW) Universe. Recently, the Hawking temperature and Bekenstein entropy have been modified for the validity of the thermodynamical laws at the event horizon. In this context, we test the validity of the generalized second law of thermodynamics (GSLT) at the apparent and event horizons. Here, the entropy of the horizon has been extracted for the following two cases: (i) by assuming the first law of thermodynamics (ii) by using modified entropy-area relation. In the case of apparent horizon, we consider the usual Hawking temperature. On the other hand, in the case of event horizon, we consider the modified Hawking temperature. Next, we discuss the geometrical parameters (deceleration, statefinder parameters and $Om$ diagnostic) to explore the expansion of the accelerating Universe. From the general expression of GSLT, we find that for the apparent horizon, the GSLT always holds for any choice of model parameters in both the branches of the DGP model. However, the null energy condition must satisfy for the plausibility of GSLT at the event horizon. Finally, we use the recent observational data from Stern datasets, Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and Type Ia Supernovae (SNIa) observations to hold down the model parameters. Our analysis reveals that the DGP braneworld is free from classical instability issues and also cannot be ruled out by present thermodynamical and observational constraints.

In 2000, Dvali et al. [4-D gravity on a brane in 5-D Minkowski space, Phys. Lett. B485 (2000) 208–214] proposed a new braneworld model named as DGP model, having two branches with $(𝜖=\pm 1)$. Former one $(𝜖=+1)$ known as accelerating branch, which explains accelerating phase of the Universe without adding cosmological constant or Dark energy (DE), whereas later one $(𝜖=-1)$ represents the decelerating branch. Here, we have investigated the behavior of Generalized Ghost Dark Energy (GGDE) under the decelerating branch of DGP model. We have studied the importance of GGDE model to explain the current phase of the Universe. To check the validity of the present model, we study the behavior of different cosmological parameters such as Hubble parameter, equation of state (EoS) parameter and deceleration parameter with respect to scale factor. Then, we have analyzed the ${\omega }_D-\acute{{\omega }_D}$ to confirm no freezing region of this study and point out thawing region. Furthermore, we have checked the gradient of stability by calculating the squared sound speed. Then, we extend our study to check the viability of this model under investigation through the analysis of statefinder diagnosis parameters for the present cosmological setup.