Acceleration of electric current-carrying string loop near a Schwarzschild black hole immersed in an asymptotically uniform magnetic field

摘要

We study the acceleration of an electric current-carrying andaxially-symmetric string loop initially oscillating in the vicinity of aSchwarzschild black hole embedded in an external asymptotically uniformmagnetic field. The plane of the string loop is orthogonal to the magneticfield lines and the acceleration of the string loop occurs due to thetransmutation effect turning in the deep gravitational field the internalenergy of the oscillating strings to the energy of their translational motionalong the axis given by the symmetry of the black hole spacetime and themagnetic field. We restrict our attention to the motion of string loop withenergy high enough, when it can overcome the gravitational attraction andescape to infinity. We demonstrate that for the current-carrying string loopthe transmutation effect is enhanced by the contribution of the interactionbetween the electric current of the string loop and the external magnetic fieldand we give conditions that have to be fulfilled for an efficient acceleration.The Schwarzschild black hole combined with the strong external magnetic fieldcan accelerate the current-carrying string loop up to the velocities close tothe speed of light $v \sim c$. Therefore, the string loop transmutation effectcan potentially well serve as an explanation for acceleration of highlyrelativistic jets observed in microquasars and active galactic nuclei.