Stellar Filaments in Self-Interacting Brans-Dicke Gravity

This paper is devoted to study cylindrically symmetric stellar filaments in self-interacting Brans-Dicke gravity. For this purpose, we construct polytropic filamentary models through generalized Lane-Emden equation in Newtonian regime. The resulting models depend upon the values of cosmological constant (due to scalar field) along with polytropic index and represent a generalization of the corresponding models in general relativity. We also investigate fragmentation of filaments by exploring the radial oscillations through stability analysis. This stability criteria depends only upon the adiabatic index.Comment: 21 pages, 4 figures, accepted for publication in EPJ

Dynamics of Axial Symmetric System in Self-Interacting Brans-Dicke Gravity

This paper investigates dynamics of axial reflection symmetric model in self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate hydrodynamical equations and discuss oscillations using time-dependent perturbation for both spin as well as spin-independent cases. The expressions of frequency, total energy density and equation of motion of oscillating model are obtained. We study instability of oscillating models in weak approximations. It is found that the oscillations and stability of the model depend upon the dark energy source along with anisotropy and reflection effects. We conclude that the axial reflection system remains stable for stiffness parameter $\Gamma=1$, collapses for $\Gamma>1$ and becomes unstable for $0<\Gamma<1$.Comment: 24 pages, no figure, accepted for publication in publication in Eur. Phys. J.

The Impact of f(G,T)f(\mathcal{G}, T) Gravity on the Evolution of Cavity in the Cluster of Stars

This paper analyzes the evolution of cavities for the cluster of stars in the context of modified Gauss-Bonnet gravity. For this purpose, we assume a spherically symmetric geometry with locally anisotropic fluid distribution. It is assumed that the proper radial distance among neighboring stellar components stays unchanged during purely areal evolution stage. We provide some analytical solutions by using general formulism in $f(\mathcal{G}, T)$ gravitation theory. The thick-shells cavities at one or both boundary surfaces are found to satisfy the Darmois conditions. Moreover, we also investigate the physical behavior of cavity models by considering the stellar $4U 1820-30$. We conclude that the dark matter has a strong impact on the evolution of cavities in the cluster of stars

Dynamics of evolving cavity in cluster of stars

We examine the evolution of cavities within spherically symmetric cluster of stars in high curvature gravity. For this purpose, we use f(R) gravity through the Starobinsky model to incorporate dark matter effects in the discussion. In particular, we check the physical significance of the f(R) model by associating it with the observational data of stellar object 4U182030. For evolution of the cavity, we consider the purely areal evolutionary phase by assuming that the proper distance (in a radial direction) among neighboring stars remains constant. The analytical solutions are obtained among which a few solutions fulfill the Darmois conditions. It is found that the evolution of the cavity in a cluster of stars is highly controlled by the influence of dark matter

Thermodynamics in modified Brans–Dicke gravity with entropy corrections

Abstract In this paper, we investigate the thermodynamics in the frame-work of recently proposed theory called modified Brans–Dicke gravity (Kofinas et al. in Class Quantum Gravity 33:15, 2016). For this purpose, we develop the generalized second law of thermodynamics by assuming usual entropy as well as its corrected forms (logarithmic and power law corrected) on the apparent and event horizons. In order to analyzed the clear view of thermodynamic law, the power law forms of scalar field and scale factor is being assumed. We evaluate the results graphically and found that generalized second law of thermodynamics holds in most of the cases

Collapsing stellar filament and exotic matter in Palatini

We explore the dynamics of collapsing stellar filament in the presence of exotic material like dark matter. We use Palatini f(R) theory to include exotic substance in the collapsing process. We derive a collapse equation by applying Darmois junction conditions on collapsing surface boundary $$\Sigma$$. It is found that the radial pressure related to baryonic matter remains non-zero at $$\Sigma$$. We then discuss the stability criteria of the collapsing process in the framework of three parameteric model, $$f(R)=R+\lambda R_{c}[ 1-(1+\frac{R^{2}}{R^{2}_{c}})^{-n}]$$. It is concluded that the stability of collapsing filament depends upon a directly proportional relation of gravitational effects of exotic terms with the radial pressure of seen matter. Stability criteria of family of polytropic filamentary structures are also discussed. For all stable polytropic filaments, it is found that the density of seen material is exponentially related to the exotic forces. Finally, we explore theoretical relation between gravitational waves and dark terms. It is theoretically predicted that the presence of exotic material can affect the propagation of gravitational waves

Aluminum-Doped Cobalt Ferrite as an Efficient Photocatalyst for the Abatement of Methylene Blue

The present study is aimed to access the photodegradation efficiency of methylene blue dye using CoFe_{2}O_{4} and Co_{0.1}Al_{0.03}Fe_{0.17}O_{0.4} nanoparticles. The synthesis of spinel ferrites nanoparticles was performed by a facile sol-gel method. The synthesized nanoparticles were characterized by FTIR, XRD, SEM, EDS, Nitrogen adsorption/desorption and UV–Visible spectroscopy. The XRD studies confirmed the spinel cubic structure of ferrite. It was also found that the crystallinity increases at an annealing temperature of 800 °C. The application of these nanoparticles for methylene blue’s photocatalytic degradation was explored and also the optimization of several parameters involving dye’s concentration, amount of catalyst and pH of the solution was done. Photocatalytic degradation of methylene blue showed that at pH 11, using 200 W visible light bulb and in 120 min; 93% methylene blue dye was degraded by using 0.1 g of Co_{0.1}Al_{0.03}Fe_{0.17}O_{0.4}