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This detail caught my eye: > [in their 1975 paper] Ashtekar and Magnon also assume that spacetime is globally hyperbolic Isn’t the modern assumption that spac
by layer8 1y ago
This detail caught my eye:
> [in their 1975 paper] Ashtekar and Magnon also assume that spacetime is globally hyperbolic
Isn’t the modern assumption that spacetime is globally flat?
- senderista 1y agoThe term refers to causal structure: https://en.wikipedia.org/wiki/Globally_hyperbolic_manifold https://en.wikipedia.org/wiki/Globally_hyperbolic_manifold
- griffzhowl 1y agoI'm just learning this stuff so the details are hazy, bu my understanding is that there's a difference between spacetime curvature and spatial curvature. You can have a hyperbolic spacetime while at the same time having a flat three-dimensional spatial section of it. It's not an assumption that space is flat. GR doesn't specify the global space curvature, so it's possible that it has a globally negative or positive curvature, but so far there's no evidence of any.