2014/04/07 by J. W. Moffat, Moffat, J. W., V. T. Toth +1
Physics and Astronomy · #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Theory (hep-th) #gr-qc #hep-th
paper · pdf · doi:10.48550/arxiv.1404.1845
3 pages; comment on Kruskal-Szekeres coordinates corrected
arxiv created 2014/04/08 · arxiv updated 2014/04/09
The Karlhede invariant is formed from the contraction of the covariant derivative of the Riemann tensor. It is a coordinate invariant that vanishes at the Schwarzschild event horizon r=2m. The vanishing of the invariant allows an observer to construct a local measuring device and use it to detect an event horizon while falling into a black hole. Recent proposals postulate the existence of a "firewall" at the event horizon that may incinerate an infalling observer. These proposals face an apparent paradox if a freely falling observer detects nothing special in the vicinity of the horizon. The behavior of Karlhede's invariant raises the possibility that the event horizon is a real physical membrane with measurable properties that are detectable by a freely falling observer.