WHEN RELATIVITY BREAKS. “A motivation for making the following analysis is to consider an alternative scenario to when the Einstein field equations (EFE) in general relativity break down. The standard concept of space-time is that it constitutes a background, with definite singularities only at points of high curvature.”
https://link.springer.com/content/pdf/10.1007/JHEP07(2019)140.pdf