Eur. Phys. J. C (2016) 76: 213
https://doi.org/10.1140/epjc/s10052-016-4058-0

Regular Article - Theoretical Physics

Penrose process in a charged axion–dilaton coupled black hole

¹ Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, UK
² Department of Theoretical Physics, Indian Association for the Cultivation of Science, Kolkata, 700 032, India

^* e-mail: tpssg@iacs.res.in

Received: 30 January 2016
Accepted: 3 April 2016
Published online: 18 April 2016

Abstract

Using the Newman–Janis method to construct the axion–dilaton coupled charged rotating black holes, we show that the energy extraction from such black holes via the Penrose process takes place from the axion/Kalb–Ramond field energy responsible for rendering the angular momentum to the black hole. Determining the explicit form for the Kalb–Ramond field strength, which is argued to be equivalent to spacetime torsion, we demonstrate that at the end of the energy extraction process, the spacetime becomes torsion free with a spherically symmetric non-rotating black hole remnant. In this context, applications to physical phenomena, such as the emission of neutral particles in astrophysical jets, are also discussed. It is seen that the infalling matter gains energy from the rotation of the black hole, or equivalently from the axion field, and that it is ejected as a highly collimated astrophysical jet.