Cosmological Analysis of Pilgrim Dark Energy in Loop Quantum Cosmology

The proposal of pilgrim dark energy is based on speculation that phantom-like dark energy (with strong enough resistive force) can prevent black hole formation in the universe. We explore this phenomenon in loop quantum cosmology framework by taking Hubble horizon as an infra-red cutoff in pilgrim dark energy. We evaluate the cosmological parameters such as Hubble, equation of state parameter, squared speed of sound and also cosmological planes like $\omega_{\vartheta}-\omega'_{\vartheta}$ and $r-s$ on the basis of pilgrim dark energy parameter ($u$) and interacting parameter ($d^2$). It is found that values of Hubble parameter lies in the range $74^{+0.005}_{-0.005}$. It is mentioned here that equation state parameter lies within the ranges $-1\mp0.00005$ for $u=2, 1$ and $(-1.12,-1), (-5,-1)$ for $u=-1,-2$, respectively. Also, $\omega_{\vartheta}-\omega'_{\vartheta}$ planes provide $\Lambda$CDM limit, freezing and thawing regions for all cases of $u$. It is also interesting to mention here that $\omega_{\vartheta}-\omega'_{\vartheta}$ planes lie in the range ($\omega_{\vartheta}=-1.13^{+0.24}_{-0.25}, \omega'_{\vartheta}<1.32$). In addition, $r-s$ planes also corresponds to $\Lambda$CDM for all cases of $u$. Finally, it is remarked that all the above constraints of cosmological parameters shows consistency with different observational data like Planck, WP, BAO, $H_0$ and SNLS.Comment: 22 pages, 20 Figure

Cosmological Evolution of Interacting New Holographic Dark Energy in Non-flat Universe

We consider the interacting holographic dark energy with new infrared cutoff (involving Hubble parameter and its derivative) in non-flat universe. In this context, we obtain the equation of state parameter which evolutes the universe from vacuum dark energy region towards quintessence region for particular values of constant parameters. It is found that this model always remains unstable against small perturbations. Further, we establish the correspondence of this model having quintessential behavior with quintessence, tachyon, K-essence and dilaton scalar field models. The dynamics of scalar fields and potentials indicate accelerated expansion of the universe which is consistent with the current observations. Finally, we discuss the validity of the generalized second law of thermodynamics in this scenario.Comment: 21 pages, 13 figure

Dynamical Instability of Shear-free Collapsing Star in Extended Teleparallel Gravity

We study the spherically symmetric collapsing star in terms of dynamical instability. We take the framework of extended teleparallel gravity with non-diagonal tetrad, power-law form of model presenting torsion and matter distribution as non-dissipative anisotropic fluid. The vanishing shear scalar condition is adopted to search the insights of collapsing star. We apply first order linear perturbation scheme to metric, matter and $f(T)$ functions. The dynamical equations are formulated under this perturbation scheme to develop collapsing equation for finding dynamical instability limits in two regimes such as Newtonian and post-Newtonian. We obtain constraint free solution of perturbed time dependent part with the help of vanishing shear scalar. The adiabatic index exhibits the instability ranges through second dynamical equation which depend on physical quantities such as density, pressure components, perturbed parts of symmetry of star, etc. We also develop some constraints on positivity of these quantities and obtain instability ranges to satisfy the dynamical instability condition.Comment: 21 pages; Accepted in EPJC for publicatio

Accretion onto Some Well-Known Regular Black Holes

In this work, we discuss the accretion onto static spherical symmetric regular black holes for specific choices of equation of state parameter. The underlying regular black holes are charged regular black hole using Fermi-Dirac Distribution, logistic distribution, nonlinear electrodynamics, respectively and Kehagias-Sftesos asymptotically flat regular black hole. We obtain the critical radius, critical speed and squared sound speed during the accretion process near the regular black holes. We also study the behavior of radial velocity, energy density and rate of change of mass for each regular black holes.Comment: 25 pages, 7 figures, Accepted for publication in Eur. Phys. J.

Effects of Thermal Fluctuations on Non-minimal Regular Magnetic Black Hole

We analyze the effects of thermal fluctuations on a regular black hole (RBH) of non-minimal Einstein-Yang-Mill theory with gauge field of magnetic Wu-Yang type and a cosmological constant. We consider the logarithmic corrected entropy in order to analyze the thermal fluctuations corresponding to non-minimal RBH thermodynamics. In this scenario, we develop various important thermodynamical quantities such as entropy, pressure, specific heats, Gibb's free energy and Helmothz free energy. We investigate first law of thermodynamics in the presence of logarithmic corrected entropy and non-minimal RBH. We also discuss the stability of this RBH using various frameworks such as $\gamma$ factor (comprises of ratio of heat capacities), phase transition, grand canonical ensemble and canonical ensemble. It is observed that the non-minimal RBH becomes more globally and locally stable if we increase the value of cosmological constant.Comment: 20 pages, 5 figure

Tidal Forces in Kiselev Black Hole

The aim of this paper is to examine the tidal forces occurred in Kiselev black hole surrounded by radiation and dust fluids. It is noted that radial and angular component of tidal force change the sign between event and Cauchy horizons. We solve the geodesic deviation equation for radially free falling bodies toward Kiselev black holes. We explain the geodesic deviation vector graphically and point out the location of event and Cauchy horizons in it for specific values of radiation and dust parameter.Comment: 20 pages, 10 figure

Thermodynamics of Black holes With Higher Order Corrected Entropy

For analyzing the thermodynamical behavior of two well-known black holes such as RN-AdS black hole with global monopole and $f(R)$ black hole, we consider the higher order logarithmic corrected entropy. We develop various thermodynamical properties such as, entropy, specific heats, pressure, Gibb's and Helmhotz free energies for both black holes in the presence of corrected entropy. The versatile study on the stability of black holes is being made by using various frameworks such as the ratio of heat capacities ($\gamma$), grand canonical and canonical ensembles, and phase transition in view of higher order logarithmic corrected entropy. It is observed that both black holes exhibit more stability (locally as well as globally) for growing values of cosmological constant and higher order correction terms.Comment: 23 pages, 10 figures, accepted for publication by Canadian Journal of Physics. arXiv admin note: text overlap with arXiv:1701.08650 by other author