On non-monotonic orbital velocity profiles around rapidly rotating Kerr-(anti)de Sitter black holes: acomment to the recently published results

Abstract

Critical discussion of the recently published results [Muller, A. and Aschenbach, B. 2007 Class. Quantum Grav. 24, p. 2637; arXiv:0704.3963] on the non-monotonic orbital velocity profiles of the Keplerian motion of test particles and l = const motion of test perfect fluid around K(a)dS black holes is given, and the discrepancies concerned the existence of the non-monotonicity in dependence of the spacetime parameters are corrected. Moreover a new non-monotonic behaviour of the Keplerian orbital velocity in the Kerr-antide Sitter spacetimes is highlighted.