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Probing of colliding wave spacetimes and a quantum Weyl conjecture

Ivo Sachs1,* and Marc Schneider2,†

  • *Contact author: ivo.sachs@lmu.de
  • †Contact author: marc.schneider@ehu.eus
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Phys. Rev. D 114, 045018 – Published 21 August, 2026

DOI: https://doi.org/10.1103/7wj9-tsyv

Abstract

We perform a quantum probing of colliding plane-wave spacetimes. In particular, we consider the Khan-Penrose and the Ferrari-Ibáñez solutions, which admit a strong and a weak singularity after the two waves collide. While we find that, like Schwarzschild, for the Khan-Penrose solution the singularity cannot be probed by quantum-field theory, the Ferrari-Ibáñez singularity can be traversed. Our results culminate in a quantum Weyl conjecture: The significant geometric property to classify spacetimes with respect to quantum probes is given by the Coulomb part of the Weyl tensor. We then use this conjecture to sketch a possible backreaction scenario for plane waves.

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Phys. Rev. D 114, 045018– Published 21 August, 2026
  • Received 6 March 2026
  • Accepted 24 July 2026
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