Null geodesics in black hole metrics with nonzero cosmological constant
Abstract
We study the radial motion along null geodesics in the ReissnerNordströmde Sitter and Kerrde Sitter spacetimes. We analyze the properties of the effective potential and we discuss circular orbits. We find that:
1)
the radius of circular photon orbits in the ReissnerNordströmde Sitter spacetimes does not depend on the cosmological constant. We show also how this is related to properties of the optical reference geometry.
2)
For a specific range of the cosmological constant, photons with high impact parameter may travel radially between the cosmological horizon and the black hole horizon in the equatorial plane of the Kerrde Sitter spacetimes.
 Publication:

General Relativity and Gravitation
 Pub Date:
 May 1991
 DOI:
 10.1007/BF00758012
 Bibcode:
 1991GReGr..23..507S