Spinning Black Holes, Spinning Flows and Spinors

Abstract

Angular momentum is an indispensable quantity perhaps in describing all the astrophysical phenomena. This is because all the cosmic objects are expected to be rotating, however be the magnitude of angular speed. The generalized astrophysical black hole is the rotating one (the Kerr black hole) which often accretes matter from its surrounding (e.g. from its binary companion) forming an accretion disk (namely X-ray binary). This accretion disk is the continuous infall of rotating matter towards a centrally located black hole (it, however, could also form around a neutron star, a white dwarf and in protoplanetary systems etc.). Hence, the flow and thus universe around a black hole is rotating/spinning in general (non-rotating accretion is a special case of it with zero angular momentum, called Bondi accretion). As black holes can not be seen directly, accretion flow around them plays indispensable roles to detect them. Now the infalling matter in accretion disks predominantly consists of protons, heavier ions, in general baryons; and electrons, neutrinos, in general leptons; all are fermions. Therefore, infalling matter predominantly consists of spinors (or spin-half particles), apart from photons which are of spin-one. In this Chapter, I aim at displaying a global picture of the interplay between three rotating/spinning entities: central black hole, accretion disk, and particles (having intrinsic spin) consisted by the disk. I show that how the underlying interplay governs important physics influencing astrophysical and gravitational phenomena remarkably.