Timeline for GR: why "background-independent" and not only "background-interacting"?
Current License: CC BY-SA 4.0
20 events
| when toggle format | what | by | license | comment | |
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| Oct 21 at 6:07 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jun 23 at 6:02 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| May 10 at 19:21 | answer | added | Níckolas Alves | timeline score: 0 | |
| May 10 at 19:07 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Nov 13, 2023 at 11:26 | comment | added | JanG | @Eletie I agree with both your sentences. The do not contradict each other in my view. The requirement of Lorentzian signature comes from physical experiment. It is some kind of boundary condition for GR mathematical theory as (3+1)-dimensional pseudo-Riemannian manifold. | |
| Nov 13, 2023 at 9:47 | comment | added | Eletie | @JanG Well GR is constructed in order to reproduce SR within its regime of validity, so it must be the case that we have a Lorentzian signature. This doesn't at all seem related to the concept of GR having a dynamical metric though. | |
| Nov 13, 2023 at 7:24 | comment | added | JanG | @Eletie It is more about metric signature in that tangent space. I came across similar view on this forum. My argument is: in our labors (so local in earth gravitation field) in experiments with electromagnetic and gravitation waves we use the fact of absoluteness of physical constant $c$ (SR). | |
| Nov 12, 2023 at 21:30 | answer | added | Void | timeline score: 0 | |
| Nov 12, 2023 at 21:15 | comment | added | Eletie | @JanG The speed of light being in constant only holds in SR, so that would be circular reasoning. Any theory based on differential manifolds has a flat tangent space | |
| Nov 12, 2023 at 18:48 | comment | added | JanG | @Eletie I can see what you mean, I agree. However, what is the reason why GR is locally (in normal coordinates) Minkowski: is it the demand of constancy of light velocity? | |
| Nov 12, 2023 at 17:39 | comment | added | Eletie | @JanG no, locally pseudo-Euclidean is a property of all differentiable manifolds. This is not the same having a fixed, non-dynamical metric $\eta$ as in SR | |
| Nov 12, 2023 at 12:05 | comment | added | JanG | @Eletie Would you agree that in GR the geometry is fixed to be locally the SR geometry? | |
| Nov 10, 2023 at 15:42 | answer | added | JanG | timeline score: 0 | |
| Nov 10, 2023 at 10:26 | comment | added | Eletie | @MartyMcFly no prior geometry is simply the expression that in GR, the geometry is not fixed a priori (e.g., it's dynamical). Contrast this to Special Relativistic theories, where the Minkowski metric is fixed a priori (non dynamical). | |
| Nov 10, 2023 at 10:04 | comment | added | MartyMcFly | @Eletie the "prior geometry" of GR is Minkowski space. Why do you say that Minkowski space is "no prior geometry"? I don't understand that. But many are arguing like this... | |
| Nov 10, 2023 at 9:13 | comment | added | Eletie | It is also synonymous with the phrase "no prior geometry", which is perhaps more obvious as to its meaning. | |
| Nov 9, 2023 at 22:32 | history | edited | Qmechanic♦ | CC BY-SA 4.0 |
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| Nov 9, 2023 at 21:58 | comment | added | Prahar | Using your analogy, the background independence refers to the fact that the artist can create “any possible object” using clay. | |
| Nov 9, 2023 at 21:56 | comment | added | Prahar | The “background” being referenced is not spacetime. It’s the geometry of spacetime. GR has the same form whether or not the background spacetime is Minkowski, Schwarzschild, Kerr, etc. In that sense its background independent. | |
| Nov 9, 2023 at 21:32 | history | asked | MartyMcFly | CC BY-SA 4.0 |