Publication date: Oct 2012
Abstract:
We study motion of current-carrying string loops in the field of
braneworld spherically symmetric black holes and naked singularities.
The spacetime is described by the Reissner-Nordström geometry with tidal
charge b reflecting the non-local tidal effects coming from the external
dimension; both positive and negative values of the spacetime parameter
b are considered. We restrict attention to the axisymmetric motion of
string loops when the motion can be fully governed by an appropriately
defined effective potential related to the energy and angular momentum
of the string loops. In dependence on these two constants of the motion,
the string loops can be captured, trapped, or can escape to infinity. In
close vicinity of stable equilibrium points at the centre of trapped
states the motion is regular. We describe how it is transformed to
chaotic motion with growing energy of the string loop. In the field of
naked singularities the trapped states located off the equatorial plane
of the system exist and trajectories unable to cross the equatorial
plane occur, contrary to the trajectories in the field of black holes
where crossing the equatorial plane is always admitted. We concentrate
our attention to the so called transmutation effect when the string
loops are accelerated in the deep gravitational field near the black
hole or naked singularity by transforming the oscillatory energy to the
energy of the transitional motion. We demonstrate that the influence of
the tidal charge can be substantial especially in the naked singularity
spacetimes with b > 1 where the acceleration to ultrarelativistic
velocities with Lorentz factor γ ~ 100 can be reached, being more than
one order higher in comparison with those obtained in the black hole
spacetimes.
Authors:
Stuchlík, Z.; Kološ, M.;