Gravity seminar - Filippo Camilloni [ONLINE SEMINAR] Seminar

Abstract: In 1977 Blandford & Znajek (BZ) initiated the analytic study of force-free magnetospheres by developing a perturbation scheme in the slow spin regime of a Kerr black hole, which lead to the discovery of a viable electromagnetic Penrose-like process for the extraction of energy and angular momentum. In this talk we offer a modern review about the BZ mechanism and the theory of Force-Free Electrodynamics. Such concepts are subsequently applied in order to construct a consistent magnetospheric solution around a Kerr black hole by means of perturbation theory combined with a matched asymptotic expansion scheme. Higher orders in the perturbative approach are featured with the unavoidable presence of non-analytic terms in the expansion parameter, which also enter the expressions for the energy extracted by the magnetosphere. These terms allow us to reach an unprecedented agreement with past numerical simulations up to the near-extreme regime and can potentially predict new features about the non-perturbative structure of the BZ theory, showing how the construction of analytic models still constitutes a powerful tool in this field. The talk is based on the paper JCAP 07 (2022) 07, 032 ArXiv[2201.11068]