https://insu.hal.science/insu-03645730Lasota, J. -P.J. -P.LasotaIAP - Institut d'Astrophysique de Paris - INSU - CNRS - Institut national des sciences de l'Univers - SU - Sorbonne Université - CNRS - Centre National de la Recherche ScientifiqueGourgoulhon, E.E.GourgoulhonAbramowicz, M.M.AbramowiczTchekhovskoy, A.A.TchekhovskoyNarayan, R.R.NarayanExtracting black-hole rotational energy: The generalized Penrose processHAL CCSD201404.70.Bw95.30.Sf95.30.Qd97.60.LfClassical black holesRelativity and gravitationMagnetohydrodynamics and plasmasBlack holesGeneral Relativity and Quantum CosmologyAstrophysics - High Energy Astrophysical Phenomena[SDU] Sciences of the Universe [physics]Sorbonne Université, Gestionnaire HAL 42022-04-24 11:20:032023-05-01 03:57:592022-04-24 11:20:03enJournal articleshttps://insu.hal.science/insu-03645730/document10.1103/PhysRevD.89.024041application/pdf1In the case involving particles, the necessary and sufficient condition for the Penrose process to extract energy from a rotating black hole is absorption of particles with negative energies and angular momenta. No torque at the black-hole horizon occurs. In this article we consider the case of arbitrary fields or matter described by an unspecified, general energy-momentum tensor T<SUB>μν</SUB> and show that the necessary and sufficient condition for extraction of a black hole's rotational energy is analogous to that in the mechanical Penrose process: absorption of negative energy and negative angular momentum. We also show that a necessary condition for the Penrose process to occur is for the Noether current (the conserved energy-momentum density vector) to be spacelike or past directed (timelike or null) on some part of the horizon. In the particle case, our general criterion for the occurrence of a Penrose process reproduces the standard result. In the case of relativistic jet-producing "magnetically arrested disks," we show that the negative energy and angular-momentum absorption condition is obeyed when the Blandford-Znajek mechanism is at work, and hence the high energy extraction efficiency up to ∼300% found in recent numerical simulations of such accretion flows results from tapping the black hole's rotational energy through the Penrose process. We show how black-hole rotational energy extraction works in this case by describing the Penrose process in terms of the Noether current.