Asymptotically Flat Radiating Solutions in Third Order Lovelock Gravity

In this paper, we present an exact spherically symmetric solution of third order Lovelock gravity in $n$ dimensions which describes the gravitational collapse of a null dust fluid. This solution is asymptotically (anti-)de Sitter or flat depending on the choice of the cosmological constant. Using the asymptotically flat solution for $n \geq 7$ with a power-law form of the mass as a function of the null coordinate, we present a model for a gravitational collapse in which a null dust fluid radially injects into an initially flat and empty region. It is found that a naked singularity is inevitably formed whose strength is different for the $n = 7$ and $n \geq 8$ cases. In the $n=7$ case, the limiting focusing condition for the strength of curvature singularity is satisfied. But for $n \geq 8$, the strength of curvature singularity depends on the rate of increase of mass of the spacetime. These considerations show that the third order Lovelock term weakens the strength of the curvature singularity.Comment: 15 pages, no figure, references added, two appendix adde

New black hole solutions of Gauss-Bonnet gravity in the presence of a perfect fluid

In this paper, the solutions of the Gauss-Bonnet theory of gravity was proposed in the presence of a perfect fluid with thermodynamic pressure P and energy gravity ρ in n-dimension. Accordingly, perfect fluid tensor was regarded as energy-momentum tensor and the static and radiating solutions for the linear equation of state p = wρ was calculated. This solution contains all the solutions already being proposed for Gauss-Bonnet gravity, such as asymptotically flat or asymptotically uncharged (anti)-de Sitter, radiating asymptotically flat and (anti)-de Sitter solutions as well as some new static and radiating solutions for different w values. We go through the properties of the new static and radiating solutions. We find solutions for w = 0 and w = (n-2)-2 in static and radiating states. We also show that the solutions satisfy the dominant and weak energy conditions and they present black holes with one or two horizons or naked singularities provided that the parameters of the solutions are chosen suitable. &nbsp