Cosmological and thermodynamics consequences of viscous modified theories of gravity

The illustration of cosmic acceleration is being presented in the framework of DGP braneworld and dynamical Chern–Simons modified gravity in the presence of casual Israel–Stewart formalism. In this way, we discuss the evolution parameter which leads to the accelerated expansion of the universe in the phantom as well as quintessence region for both gravities. The squared speed of sound [Formula: see text] leads to the stable behavior of the current physical system in both gravities in the later epoch. Also, the entropy variation, as well as thermal equilibrium condition, remains valid in both frameworks at the present and later epoch.

Thermodynamic and observational constraints of DGP braneworld in the light of nonlinear electrodynamics

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 [Formula: see text] 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.

Ghost Dark Energy in the DGP Braneworld

We investigate the ghost model of dark energy in the framework of DGP braneworld. We explore the cosmological consequences of this model by determining the equation of state parameter, ωD, the deceleration, and the density parameters. We also examine the stability of this model by studying the squared of the sound speed in the presence/absence of interaction term between dark energy and dark matter. We find out that in the absence of interaction between two dark sectors of the universe we have ωD→-1 in the late time, while in the presence of interaction ωD can cross the phantom line -1. In both cases the squared of sound speed vs2 does not show any signal of stability. We also determine the statefinder diagnosis of this model as well as the ωD-ωD′ plane and compare the results with the ΛCDM model. We find that ωD-ωD′ plane meets the freezing region in the absence of interaction between two dark sectors, while it meets both the thawing and the freezing regions in the interacting case.

Cosmological implications of DGP braneworld via well-known holographic dark energy models

The cosmological analysis is being studied in the present work in Dvali–Gabadadze–Porrati (DGP) braneworld scenario by taking various interacting modified holographic dark energy (HDE) models. We discuss the various cosmological parameters such as deceleration parameter, equation-of-state (EoS) parameter and squared speed of sound. It is found that the trajectories of deceleration parameter exhibit in accelerated phase of the universe for all models. The EoS parameter corresponds to various phases of cosmic acceleration like quintessence, vacuum, phantom and also exhibits consistency with observational data. The squared speed of sound also gives stability of models in the current scenario. The [Formula: see text] also gives consistent results with various observational schemes. The statefinders plane also exhibits the cosmic acceleration. It is interesting to remark here that some of our results shows consistency with observational data like WMAP+CMB+BAO+[Formula: see text]+SNe.