Publication date: Jul 2000
Abstract:
Properties of the optical reference geometry related to Kerr-Newman
black-hole and naked-singularity spacetimes are illustrated using
embedding diagrams of their equatorial plane. It is shown that among all
inertial forces defined within the framework of the optical geometry,
just the centrifugal force plays a fundamental role in connection with
the embedding diagrams because it changes sign at the turning points of
the diagrams. The embedding diagrams do not cover the stationary part of
the Kerr-Newman spacetimes completely. Hence, the limits of
embeddability are given, and it is established which of the photon
circular orbits hosted by the Kerr-Newman spacetimes appear in the
embeddable regions. Some typical embedding diagrams are constructed, and
the Kerr-Newman backgrounds are classified according to the number of
embeddable regions of the optical geometry as well as the number of
their turning points. It is shown that embedding diagrams are closely
related to the notion of the radius of gyration which is useful for
analysing a fluid rotating in strong gravitational fields.
Authors:
Stuchlík, Z.; Hledík, S.; Jurán, J.;