> Postdoc research? I obviously can't speak for everyone but, yes, at least it's been my impression that mathematical GR as a research field in mathematics is

> Postdoc research? I obviously can't speak for everyone but, yes, at least it's been my impression that mathematical GR as a research field in mathematics is quite disconnected from physics and its existence, to some, completely unknown. Only very few people like Chruściel manage to bridge the gap and talk to and collaborate with people on both sides. To give a few data points: If you mostly do research on e.g. gravitational waves (think LIGO) you're usually far away from the typical geometric-analytical questions surrounding the foundations of GR and much more concerned with e.g. numeric simulations, elimination and modeling of noise and systematic errors, machine learning and such. Years ago, I talked to a professor in theoretical high-energy physics (mostly string theory / supergravity) and asked him for career advice because I wanted to do research on gravity and especially black holes. He told me that "GR as a research field is dead" and that, if I wanted to study black holes, there was "no way around string theory". Sure, he was probably biased and clearly living in a bubble relatively far away from "classic GR" but it still says a lot I would say. I mean even the people working on the Event Horizon Telescope don't know too much about mathematical/foundational questions in GR. They are much more interested in modeling and solving their specific problems, in this case: radioastronomical problems, problems in relativistic plasma physics etc. (Source: I have spoken to two leading scientists at the EHT about mathematical questions surrounding GR.)