**Publication date:** Dec 2010

**Abstract:**

Current-carrying string loop dynamics in Schwarzschild-de Sitter

spacetimes characterized by the cosmological parameter

λ=(1)/(3)ΛM2 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<λtrap˜0.00497. The trapped

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

down to rmt˜3.3M.

**Authors:**

Kološ, M.; Stuchlík, Z.;