**Publication date:** Dec 2010

**Abstract:**

Current-carrying string loop dynamics in Schwarzschild-de Sitter

spacetimes characterized by the cosmological parameter

λ=(1)/(3)ΛM^{2} is investigated. With attention concentrated to

the axisymmetric motion of string loops 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 black hole

gravitational field given by the mass M and the cosmic repulsion given

by the cosmological constant Λ. The gravitational attraction could cause

capturing of the string having low energy by the black hole or trapping

in its vicinity; with high enough energy, the string can escape

(scatter) to infinity. The role of the cosmic repulsion becomes

important in vicinity of the so-called static radius where the

gravitational attraction is balanced by the cosmic repulsion—it is

demonstrated both in terms of the effective potential of the string

motion and the basin boundary method reflecting its chaotic character,

that a potential barrier exists along the static radius behind which no

trapped oscillations may exist. The trapped states of the string loops,

governed by the interplay of the gravitating mass M and the cosmic

repulsion, are allowed only in Schwarzschild-de Sitter spacetimes with

the cosmological parameter λ<λ_{trap}̃0.00497. The trapped

oscillations can extend close to the radius of photon circular orbit,

down to r_{mt}̃3.3M.

**Authors:**

Kološ, M.; Stuchlík, Z.;