2 very sensitive measurements conducted within the past year seem to suggest (if GR is true), that we are in a universe that lacks causality. 2/3 LIGO detections imply one of the merging pair of black holes should be a naked singularity.

GR allows naked singularities. It models them fine. GR just stops being globally deterministic.

If you look up the history of GR some mathematicians in 50's made some really weird proposals for non-causal universes that would appear locally causal. But there isn't a way to test this. So it is more pure mathematics or philosophy then physics.

http://mnras.oxfordjournals.org/content/162/4/307.abstract discusses observables of such metrics, especially Gödel's.

A 2009 overview (postdating COBE, for example): http://iopscience.iop.org/article/10.1088/0004-637X/703/1/35... (preprint: https://arxiv.org/abs/0902.4575)

> 2/3 LIGO detections imply one of the merging pair of black holes should be a naked singularity.

Where did you get that from?

It's sure not prominent on the caltech or mit sites, or indeed in Pretorius et al. https://arxiv.org/abs/1603.08955

Where did you get this impression? All of the LIGO results are consistent with "standard" GR black holes whose event horizons merge.

Background: https://en.wikipedia.org/wiki/Gravastar

This creates more interest, but can obfuscate what the real situation in the field is. In this case, while Gravastars are certainly something many scientists actively do and should consider, there is no real evidence from the LIGO data that favors the hypothesis of "we are in a universe that lacks causality" over the observation of the merger of two Kerr black holes.

Yes.

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.94.084... (preprint: https://arxiv.org/abs/1602.08759)

So you're still left with gravastar models that can co-exist with black holes.

One of the key assumptions of GR is that spacetime is globally hyperbolic. This implies causality. You can’t guarantee solutions of the Einstein or Maxwell equations w/o this assumption.

link?

ED: This is the starting point of the Causal Set [1] program. Don’t ask me for details, I don’t know any. But the wikipedia article looks interesting. Seems they are trying to figure out how causality restricts models with some level of discreteness.

[1] https://en.wikipedia.org/wiki/Causal_sets