Bianchi Type-III Spacetime and Generalized Cosmic Chaplygin Gas

Bianchi type-III cosmological model with generalized cosmic Chaplygin gas equation of state has been studied in general theory of relativity. To characterize different phases of the universe, the statefinder diagnostic pair {r,s} has been adopted. We investigated the stability of the model and also discussed the physical and geometrical properties

Role of a periodic varying deceleration parameter in Particle creation with higher dimensional FLRW Universe

The present search focus on the mechanism of gravitationally influenced particle creation (PC) in higher dimensional Friedmann-Lemaitre-Robertson-Walker(FLRW) cosmological models with a cosmological constant (CC). The solution of the corresponding field equations is obtained by assuming a periodically varying deceleration parameter (PVDP) i.e. $q= m \cos kt - 1$ [Shen and Zhao, Chin. Phys. Lett., 31 (2014) 010401] which gives a scale factor $a(t) = a_0 \left[\tan \left(\frac{kt}{2}\right)\right]^\frac{1}{m}$, where $a_0$ is the scale factor at the current epoch. Here $k$ displays the PVDP periodicity and can be regarded as a parameter of cosmic frequency, $m$ is an enhancement element that increases the PVDP peak. Here, we investigated the periodic variation behavior of few quantities such as the deceleration parameter $q$, the energy density $\rho$, PC rate $\psi$, the entropy $S$, the CC $\Lambda$, Newton's gravitational constant $G$ and discuss their physical significance. We have also explored the density parameter, proper distance, angular distance, luminosity distance, apparent magnitude, age of the universe, and the look-back time with redshift $z$ and have observed the role of particle formation in-universe evolution in early and late times. The periodic nature of various physical parameters is also discussed which are supporting the recent observations.Comment: 19 pages, 15 figure

Observation constraints on scalar field cosmological model in Anisotropic universe

In this study, we have explored a scalar field cosmological model in the axially symmetric Bianchi type-I universe. In this study, our aim is to constrain the scalar field dark energy model in an anisotropic background. For this purpose, the explicit solution of the developed field equations for the model is determined and analysed. Constraints on the cosmological model parameters are established utilizing Markov Chain Monte Carlo (MCMC) analysis and using the latest observational data sets of OHD, BAO, and Pantheon. For the combined dataset (OHD, BAO, and Pantheon), the best-fit values of Hubble and density parameters are estimated as $H_{0} = 71.54\pm 0.28$, $\Omega_{m0}=0.2622\pm0.0021$ $\Omega_{\phi0} = 0.7331\pm0.0046$, and $\Omega_{\sigma 0} = 0.000162\pm0.000063$. The model shows a flipping nature and redshift transition occurs at $z_{t} = 0.6964^{+0.0136}_{-0.0006}$, and the present value of decelerated parameter is computed to be $q_{0} = -0.6964\pm0.028$ for the combined dataset. We have explored characteristics like the universe's age, particle horizon, deceleration parameter, and jerk parameter. The dynamical properties such as energy density $\rho_{\phi}$, scalar field pressure $p_{\phi}$, and equation of state parameter $\omega_{\phi}$ are analyzed and presented. We have also described the behavior of the scalar potential $V(\phi)$ and scalar fields. Furthermore, the authors also described the behavior of energy conditions in scalar-tensor cosmology. The scenario of the present accelerated expansion of the universe is described by the contribution of the scalar field.Comment: 18 Pages, 15 figure