Publication date: Sep 2013
Current-carrying string-loop dynamics is studied in the Kerr spacetimes.
With attention concentrated to the axisymmetric motion of string loops
around the symmetry axis of both black-hole (BH) and naked singularity
(NS) spacetimes, it is shown that the resulting motion is governed by
the presence of an outer tension barrier and an inner angular momentum
barrier that are influenced by the BH or NS spin. We classify the string
dynamics according to properties of the energy boundary function
(effective potential) for the string loop motion. We have found that for
NS there exist new types of energy boundary function, namely those with
off-equatorial minima. Conversion of the energy of the string
oscillations to the energy of the linear translational motion has been
studied. Such a transmutation effect is much more efficient in the NS
spacetimes because of lack of the event horizon. For BH spacetimes
efficiency of the transmutation effect is only weakly spin dependent.
Transition from the regular to chaotic regime of the string-loop
dynamics is examined and used for explanation of the string-loop motion
focusing problem. Radial and vertical frequencies of small oscillations
of string loops near minima of the effective potential in the equatorial
plane are given. These can be related to high-frequency quasiperiodic
oscillations observed near black holes.
Kološ, M.; Stuchlík, Z.;