Onyx
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- TL;DR Summary
- Wick-rotated riemannian metric that takes leaky gravity into account
This is pretty theoretical, so I don't know whether it would better belong in the "other physics" section. As I understand it, a pair of pants situation of topology change where one universe splits in two is described by a global wick-rotated riemannian metric so as to avoid the causality violations that would arise from a global lorentzian description. I think even if the metric is piecewise and/or discontinuous, that is okay, so long as it avoids CTCs. Now, philosophically speaking, what resides between the universes can be two things. In the purely intrinsic description, the question is without meaning. But the alternative is that it is the bulk between two branes. And this is where the question arises: the wick-rotation is done so that one brane branch is causally disconnected from the other, but of course we know that (at least in the brane theories I've heard) gravity can leak through. So I guess the question then becomes, how do we make a space that becomes two causally disconnected (geodesic and arbitrary curve wise) spaces but yet the local curvature in one brane can leak through the bulk to the other?