journal club on aspects of information, quantum theory, and gravity
15 Jul 2025
We review Kerr’s paper which raises questions regarding the relation between trapped surfaces, null geodesics of finite affine length, and spacetime singularities. His main argument lies on counter-examples to the theorems proven by Hawking and Penrose, in which he analyzes principal null geodesic congruences on Kerr spacetime. However, it is evident that his argument is based on the behavior of a bad coordinate system, and thus, does not represent a fundamental property of spacetime. Nevertheless, Kerr raises an important point on how to actually interpret the singularity theorems, in particular, the claim that all black holes contain singularities. Following this discussion, we also pose a question on the theoretical prediction of black holes and their experimental confirmation.