Activity for preguntonâ€
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Answer | — |
A: Creating a wormhole connecting two universes with different spacetime metrics? Within general relativity at least, I think this is impossible. The metric tensor of a pseudo-Riemannian manifold is usually taken to be everywhere nondegenerate (see e.g. this source. A metric is nondegenerate when its determinant is nonzero, or equivalently when it has no $0$ eigenvalues), but for ... (more) |
— | over 5 years ago |
| Answer | — |
A: The mass of an economically feasible non-microscopic traversable wormhole I finally found how to calculate the mass in the general case. Here is an answer summarizing my comments and calculations (but I'm still not an expert in general relativity, so please take it with a grain of salt). Mass in general relativity can be a tricky concept. In particular, the ADM mass of ... (more) |
— | almost 6 years ago |
| Question | — |
Would planets be cubic in my "cuboverse"? Summary The main idea behind the "cuboverse" is that spacetime distances are measured by (something close to) the sup norm or infinity norm. Under this norm, spheres (the set of points at a fixed distance from an origin) are the same as cubes, hence the name. Other features that I have been able to... (more) |
— | over 6 years ago |