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.
Highlights
The energy extraction process from the black hole following the Penrose process gave rise to a new understanding of black hole mechanics
Thermodynamic principles associated with black hole geometry gained enormous interest in recent times in the context of string theory where different kinds of black holes have been investigated in the light of this principle
Newman and Janis [1,2] showed that different kinds of inequivalent black holes can be obtained from known solutions; for example, from the Schwarzschild black hole, the Kerr solution can be obtained, while the Kerr–Newman metric emerges from the Reissner–Nordstrom geometry using the Newman–Janis prescription
Summary
The energy extraction process from the black hole following the Penrose process gave rise to a new understanding of black hole mechanics. Newman and Janis [1,2] showed that different kinds of inequivalent black holes can be obtained from known solutions; for example, from the Schwarzschild black hole, the Kerr solution can be obtained, while the Kerr–Newman metric emerges from the Reissner–Nordstrom geometry using the Newman–Janis prescription. It is well known in a string inspired scenario that in four space-time dimensions, the massless axions are dual to the third rank field strength of a second rank antisymmetric tensor field (known as Kalb–Ramond field) which appears in the massless sector of closed bosonic string theories. C (2016) 76:213 cles in astrophysical jets, believed to be from rotating black holes
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