Dynamics of current-carrying string loops in the Kerr naked-singularity and black-hole spacetimes

Abstract

Current-carrying string-loop dynamics is studied in the Kerr spacetimes. With attention concentrated to the axisymmetric motion of string loops around 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 lack of the event horizon. For BH spacetimes efficiency of the transmutation effect is only weakly spin dependent. Transition from 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 quasi-periodic oscillations observed near black holes.

Disclosing connections between black holes and naked singularities: horizon remnants, Killing throats and bottlenecks

“…However, in general, they are also differently defined as strong curvature singularities, for example, in [19]. Regarding various NSs properties and characteristics of the gravitational collapse, possible formation and stability of naked singularities as well as other analysis concerning observational phenomena related to possible NSs existence, we refer also to [20][21][22][23][24][25][26][27][28][29][30][31][32][33][37][38][39][40][41]. In this work, WNSs are characterized by spin-mass ratios close to the value of the extreme BH.…”

Charged string loops in Reissner–Nordström black hole background

“…Recall that evolution of axisymmetric string loops adjusted to axisymmetric backgrounds can be represented by evolution of a single point of the string [21,10]. We can also compare electromagnetic forces acting on charge test particles or string loops.…”

“…Detailed studies of relativistic current-carrying string loops moving axisymmetrically along the symmetry axis of Kerr or Schwarzschild-de Sitter black holes appeared currently [8,10,9]. Tension of such string loops prevents their expansion beyond some radius, while their world-sheet current introduces an angular momentum barrier preventing collapse into the black hole.…”

“…The general dynamics of motion for relativistic current and charge carrying string loop with tension µ and scalar field ϕ was introduced by [13] for the spherically symmetric Schwarzschild BH spacetimes, for the Kerr spacetimes it is discussed in [11,14,8,10]. General Hamiltonian form for all axially symmetric spacetimes also with electromagnetic field is introduced by [13].…”

“…We show that there are similarities in the dynamics of the charged string loops and charged test particles, as the dynamics can be described in both cases by the Hamiltonian formalism with a relatively simple effective potential. There is a fundamental difference in the RN backgrounds: while the test particle motion is regular, the string loop motion has in general chaotic character [13,10], where "islands" of regularity occur only for small oscillations near the string loop stable equilibrium points.…”