Effects of Electromagnetic Field on The Collapse and Expansion of Anisotropic Gravitating Source

This paper is devoted to study the effects of electromagnetic on the collapse and expansion of anisotropic gravitating source. For this purpose, we have evaluated the generating solutions of Einstein-Maxwell field equations with spherically symmetric anisotropic gravitating source. We found that a single function generates the various anisotropic solutions. In this case every generating function involves an arbitrary function of time which can be chosen to fit several astrophysical time profiles. Two physical phenomenon occur, one is gravitational collapse and other is the cosmological expanding solution. In both cases electromagnetic field effects the anisotropy of the model. For collapse the anisotropy is increased while for expansion it deceases from maximum value to finite positive value. In case of collaps there exits two horizons like in case of Reissner-Nordstr$\ddot{o}$m metric.Comment: 16 pages, 5 figures. Accepted for Publication in Astrophysics and Space Science. An updated version to be matched with Accepted versio

Dynamics of Charged Radiating Collapse in Modified Gauss-Bonnet Gravity

This paper deals with the dynamics of a shearfree charged radiating collapse in modified Gauss-Bonnet gravity. The field equations for shearfree spherical interior geometry of a charged dissipative star are formulated. To study the dynamical behavior of collapsing matter, we derive the dynamical as well as transport equations. We conclude that the gravitational force in modified Gauss-Bonnet gravity is much stronger as compared to general relativity which implies the increase in the rate of collapse. Finally, we study the effect of charge on the dynamics of collapse.Comment: 15 pages, no figure, Accepted for publication in Eur. Phys. J. Plus. arXiv admin note: text overlap with arXiv:1302.117

Models of Anisotropic Self-Gravitating Source in Einstein-Gauss-Bonnet Gravity

In this paper, we have studied gravitational collapse and expansion of non-static anisotropic fluid in $5D$ Einstein Gauss-Bonnet gravity. For this purpose, the field equations have been modeled and evaluated for the given source and geometry. The two metric functions have been expressed in terms of parametric form of third metric function. We have examined the range of parameter $\beta$ (appearing in the form of metric functions) for which $\Theta$ the expansion scalar becomes positive/negative leads to expansion/collapse of the source. The trapped surface condition has been explored by using definition of Misner-Sharp mass and auxiliary solutions. The auxiliary solutions of the field equations involve a single function which generates two types of anisotropic solutions. Each solution can be represented in term of arbitrary function of time, this function has been chosen arbitrarily to fit the different astrophysical time profiles. The existing solutions forecast gravitational expansion and collapse depending on the choice of initial data. In this case, it has been investigated wall to wall collapse of spherical source. The dynamics of the spherical source has been observed graphically with the effects of Gauss-Bonnet coupling term $\alpha$ in the case of collapse and expansion. The energy conditions are satisfied for the specific values of parameters in the both solutions, this implies that the solutions are physically acceptable.Comment: 20 pages,16 Figures, Title Changed, Major revision included,accepted version to appear in Adv.High Energy Physic

Cardy-Verlinde Formula of Non-Commutative Schwarzschild Black Hole

Few years ago, Setare \cite{1} has investigated the Cardy-Verlinde formula of non-commutative black hole obtained by non-commutativity of coordinates. In this paper, we apply the same procedure to a non-commutative black hole obtained by the co-ordinate coherent approch. The Cardy-Verlinde formula is entropy formula of conformal field theory in an arbitrary dimension. It relates the entropy of conformal filed theory to its total energy and Casimir energy. In this paper, we have calculated the total energy and Casimir energy of non-commutative Schwarzschild black hole and have shown that entropy of non-commutative Schwarzschild black hole horizon can be expressed in terms of Cardy-Verlinde formula.Comment: 9 Pages, no figures, Accepted for Publication in Advances in High Energy Physics. Some typos remove

Existence of stable wormholes on a noncommutative-geometric background in modified gravity

In this paper, we discuss spherically symmetric wormhole solutions in $f(R,T)$ modified theory of gravity by introducing well-known non-commutative geometry in terms of Gaussian and Lorentizian distributions of string theory. For some analytic discussion, we consider an interesting model of $f(R,T)$ gravity defined by $f(R,T)=f_{1}(R)+\lambda T$. By taking two different choices for the function $f_{1}(R)$, that is, $f_{1}(R)=R$ and $f_{1}(R)=R+\alpha R^{2}+\gamma R^{n}$, we discuss the possible existence of wormhole solutions. In the presence of non-commutative Gaussian and Lorentizian distributions, we get exact and numerical solutions for both these models. By taking appropriate values of the free parameters, we discuss different properties of these wormhole models analytically and graphically. Further, using equilibrium condition, it is found that these solutions are stable. Also, we discuss the phenomenon of gravitational lensing for the exact wormhole model and it is found that the deflection angle diverges at wormhole throat.Comment: 15 pages, 18 figure