GRG Editor's Choice: Examining the Kerr metric through wave fronts of null geodesics

© SpringerKling, T.P., Grotzke, E., Roebuck, K., Waite, H., Examining the Kerr metric through wave fronts of null geodesics, Gen Relativ Gravit (2019) 51: 32.

Editor's Choice (Research Article)

First Online: 20 February 2019

"Very interesting work. I especially like the clarity of the presentation of the subject and I consider visualisations a vital ingredient to enhance our understanding of black hole physics. it is definitely worth publishing in the hope that the follow-up connection to observable properties will be subsequently investigated."


We examine the singularities of the wave fronts of null geodesics from point sources in the Kerr metric. We find that the wave fronts develop a tube like structure that collapses non-symmetrically, leading to cusp features in the wave front singularities. As the wave front advances, the cusps trace out an astroidal shaped caustic tube, which had been discovered previously using lens mapping and geodesic deviation methods. Thus, the wave front approach in this study helps to complete a picture of caustics and gravitational lensing in the Kerr geometry.

The authors: 

Thomas P. Kling is Professor of Physics at Bridgewater State University. His research is in the application of general relativity to light rays through gravitational lensing.

Eric Grotzke and Kevin Roebuck are graduate students studying relativity at Wake Forest University. 

Harry Waite completed a M.S. in Physics from the University of Massachusetts Dartmouth and is working the private sector.

GRG Editor's Choice:

In each volume of GRG, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community.