Recent content by Demystifier

The pressure of the water is ##p = \rho g h##, so gravity enters through the ##g##. But the force of the water ##pA## (where ##A## is the area) acting upwards has to be balanced by the gravitational force ##mg## acting downwards, so the ##g##'s cancel, i.e. the draft does not depend on gravity.

Schrodinger equation is similar to the Hamilton-Jacobi equation, so I find intuitive the interpretation in which the wave function is analogous to the Hamilton-Jacobi function.

Yes, but the Schwarzschild spacetime is unphysical, in the sense that it describes an eternal black hole. A physical black hole is a result of a gravitational collapse, it deviates from Schwarzschild spacetime, and this deviation is associated with a realistic energy-momentum.

I guess you mean Riemann tensor, because, according to GR, Ricci tensor cannot change without a change of energy-momentum.

What is a physical cause of boundary conditions, if not a presence of energy-momentum?

What else can change, if not the stress-energy tensor?

At least sometimes one does. For definiteness, let us consider the example of the Kerr metric.

I see your point, but in GR one usually thinks backwards. One first finds an analytic expression for the metric tensor (usually as a solution of the Einstein equation), and then tries to reconstruct the global topology of the manifold. It seems to me that this reconstruction is somewhat...

Your very question proves me right, because you ask about the physical meaning, namely about the interpretation. But I meant it as an exercise in differential geometry, that has nothing to do with physics.

I'm not sure about that. Suppose that someone tells you that the Schwarzschild ##g_{\mu\nu}(t,r,\theta,\varphi)## is not a metric tensor, but just some tensor on a 4-dimensional manifold with unspecified metric. Would that influence your conclusions about the global topology of the manifold? If...

The difference between Schwarzschild metric and black hole spacetime is in the interpretation of the interior behind the horizon. But we don't know what happens behind the horizon and there are theoretical indications (e.g. related to the information paradox) that the usual GR picture of physics...

There is a classical version of this. Formulate gravity as a spin-2 field on a Minkowski background. Develop a perturbative method of classical scattering computation, which leads to classical Feynman diagrams (differing from the quantum Feynman diagrams by having no loop diagrams). The internal...

Why do you think I'm sure? But as Dale said, that's off topic.

Excellent! I like the idea that, at some small distance scale, the space is discrete rather than continuous. If true, then the fundamental theory does not have a local part at all, suggesting that there is no fictitious force at all. I know that you don't like wild speculations, but I couldn't...

I have no problems with accepting that gravity is a fictitious force according to GR. But physicists are used to think that the theories they have are only effective approximate theories, which one day may be superseded by better theories. So suppose that one day GR is replaced by a better...