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I'm curious if anyone has seriously explored the GR math of space with "bubbles" that may turn pretty big in case of black holes. The spacetime wraps around tho
by akomtu 4y ago
I'm curious if anyone has seriously explored the GR math of space with "bubbles" that may turn pretty big in case of black holes. The spacetime wraps around those bubbles, so the only way to detect such bubbles is observing the GR effects. My impression so far has been that GR theorists assume that the spacetime is continuous - it may be distorted here and there, but overall it's a smooth "pile of space" homeomorphic to a sphere.
- codethief 4y agoThat is a very good question which I've been thinking about for years: How is it that at cosmological scales it is reasonable (apparently) to assume that the matter density of the universe is homogenous (i.e. the same everywhere) in space, yet at a local level, we have Schwarzschild/Kerr spacetimes around every spherically symmetric body (whether black hole, star, planet or atom)? How does a homogeneous universe emerge from this "bubbly" spacetime, as you call it, at larger scales? Unfortunately, Einstein's field equations are not linear, so in contrast to other (linear) field theories, this case is not as simple as superposing several black hole solutions to a global solution and then averaging or zooming out in an appropriate way, since the sum of two solutions won't give another solution. I'm wondering whether anyone has ever looked into the scaling behavior of the Einstein field equations but the answer from most people in the community that I've talked to has been no.