caa a22 4500 467887071 CHVBK 20180406152737.0 cr unu---uuuuu 170328e20061201xx s 000 0 eng 10.1007/s10714-006-0346-6 doi (NATIONALLICENCE)springer-10.1007/s10714-006-0346-6 MacCallum Malcolm School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, E1 4NS, London, UK aut On singularities, horizons, invariants, and the results of Antoci, Liebscher and Mihich (Gen Relativ Gravit 38, 15 (2006) and earlier) [Elektronische Daten] [Malcolm MacCallum] Antoci etal. have argued that the horizons of the boost-rotation, Kerr and Schwarzschild solutions are singular, having shown that a certain invariantly defined acceleration scalar blows up at the horizons. Their examples do not satisfy the usual definition of a singularity. It is argued that using the same term is seriously misleading and it is shown that such divergent functions are natural concomitants of regular horizons. In particular it is noted that the divergence is given by the special relativistic approximation to the overall metric. Earlier work on characterization of horizons by invariants is revisited, a new invariant criterion for them is proposed, and the relation of the acceleration invariant to the Cartan invariants, which are finite at the horizons and completely determine the spacetimes, is examined for the C-metric, Kerr and Schwarzschild cases. An appendix considers coordinate identifications at axes and horizons. Springer Science+Business Media, LLC, 2006 General Relativity and Gravitation Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 38/12(2006-12-01), 1887-1899 0001-7701 38:12<1887 2006 38 10714 https://doi.org/10.1007/s10714-006-0346-6 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10714-006-0346-6 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- MacCallum Malcolm School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, E1 4NS, London, UK aut NATIONALLICENCE 773 0- General Relativity and Gravitation Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 38/12(2006-12-01), 1887-1899 0001-7701 38:12<1887 2006 38 10714 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer