Particle Collision near 1+1- Dimensional Horava-Lifshitz Black Hole and Naked Singularity

The unbounded center of mass (CM) energy of oppositely moving colliding particles near horizon emerge also in 1+1- dimensional Horava-Lifshitz gravity. This theory has imprints of renormalizable quantum gravity characteristics in accordance with the method of simple power counting. Surpris- ingly the result obtained is not valid for a 1- dimensional Compton- like process between an outgoing photon and an infalling massless/ massive particle. It is possible to achieve unbounded CM energy due to collision between infalling photons and particles. The source of outgoing particles may be at- tributed to an explosive process just outside the horizon for a black hole and the naturally repulsive character for the case of a naked singularity. It is found that absence of angular momenta in 1+1- dimensions does not yield unbounded energy for collisions in the vicinity of naked singularities.Comment: 9 pages, To be published in the Advances in High Energy Physics, The special issue of "Dark Matter and Dark Energy Cosmologies and Alternative Theories of Gravitation

Uninformed Hawking Radiation

We show in detail that the Parikh-Wilczek tunneling method (PWTM), which was designed for resolving the information loss problem in Hawking radiation (HR)fails whenever the radiation occurs from an isothermal process. The PWTM aims to produce a non-thermal HR which adumbrates the resolution of the problem of unitarity in quantum mechanics (QM), and consequently the entropy (or information) conservation problem. The effectiveness of the method has been satisfactorily tested on numerous black holes (BHs). However, it has been shown that the isothermal HR, which results from the emission of the uncharged particles of the linear dilaton BH (LDBH) described in the Einstein-Maxwell-Dilaton (EMD) theory, the PWTM has vulnerability in having non-thermal radiation. In particular, we consider Painlev\'e-Gullstrand coordinates (PGCs) and isotropic coordinates (ICs) in order to prove the aformentioned failure in the PWTM. While carrying out calculations in the ICs, we also highlight the effect of the refractive index on the null geodesics.Comment: 4 pages, minor corrections, corrected typo

Thin-shell wormholes from the regular Hayward black hole

We revisit the regular black hole found by Hayward in $4-$dimensional static, spherically symmetric spacetime. To find a possible source for such a spacetime we resort to the non-linear electrodynamics in general relativity. It is found that a magnetic field within this context gives rise to the regular Hayward black hole. By employing such a regular black hole we construct a thin-shell wormhole for the case of various equations of state on the shell. We abbreviate a general equation of state by $p=\psi \left( \sigma \right)$ where $p$ is the surface pressure which is the function of the mass density ($\sigma$). In particular, a linear, logarithmic, Chaplygin, etc. forms of equations of state are considered. In each case we study the stability of the thin-shell against linear perturbations. We plot the stability regions by tuning the parameters of the theory. It is observed that the role of the Hayward parameter is to make the TSW more stable. Perturbations of the throat with small velocity condition is also studied. The matter of our TSWs, however, remains to be exotic.Comment: 7 pages 5 figures, extended versio