Eur. Phys. J. C (2022) 82: 209
https://doi.org/10.1140/epjc/s10052-022-10108-3

Regular Article - Theoretical Physics

Testing generalized spacetimes for black holes using the Hod function representation of the hoop conjecture

¹ Zel’dovich International Center for Astrophysics, M. Akmullah Bashkir State Pedagogical University, 3A, October Revolution Street, 450008, Ufa, RB, Russia
² Department of Physics and Astronomy, Bashkir State University, 47A, Lenin Street, 453103, Sterlitamak, RB, Russia
³ Salavat Industrial College, 27, Matrosova Boulevard, 453259, Salavat, RB, Russia

Received: 6 January 2022
Accepted: 5 February 2022
Published online: 9 March 2022

Abstract

The hoop conjecture, due to Thorne, is a fundamental aspect of black holes in classical general relativity. Recently, generalized classes of regular spherically symmetric static black holes with arbitrary exponents coupled to nonlinear electrodynamics have been constructed in the literature. The conjecture in those spacetimes could be violated if only the asymptotic mass $M_{\infty }$ is used. To avoid such violations, Hod earlier suggested the appropriate mass function and stated the conjecture in terms of what we call the Hod function. The conjecture can then be applied to any given static spacetime to test whether or not it represents black holes. It is shown here that the conjecture is protected in the above constructed class of generalized spacetimes thus supporting them as black holes. However, it is argued that there are factors, including violation of the conjecture, that militate against the proposed new class of solutions to be qualifying as black holes. Finally, we exemplify that the Hod mass $M(r\le R)$ in the conjecture is exactly the matter counterpart of the Misner–Sharp geometrical quasilocal mass $m(r\le R)$ of general relativity. Thus any conclusion based on Hod function is strictly a conclusion of general relativity.