33 research outputs found
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 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 where is the
surface pressure which is the function of the mass density (). 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