Recent content by Gio83

Einstein's field equations (EFEs) describe the pointwise relation between the geometry of the spacetime and possible sources described by an energy-momentum tensor ##T^{ab}##. As well known, such equations can be derived from a variational principle applied to the following action: $$S=\int\...

I was certainly not referring to a possible limitation of General Relativity. I'm aware that issues that are present in some circumstances can be resolved by enforcing the diffeomorphism invariance. You are right, if I'm to describe a dynamical situation I cannot appeal to a static metric...

Hi everyone, I'm not aware if a similar question has already been posed, so if this is the case I apologize and I beg you to redirect me to the relevant discussion. In the context of General Relativity, the Schwarzschild solution in the frame of reference of an observer at fixed distance...

thanks a lot, all of you!

Yes, the density of matter is a decreasing function of time due to the expansion of space, right? But I was wondering if this decrease of density could affect the geometry of the universe, changing the value of k. Say, during a phase of high density the universe could be described by a closed...

In the expression of the Robertson-Walker metric for an expanding universe, the parameter k is allowed to be 1, -1, 0 if the universe is respectively closed, open or flat. But Einstein says that the density of the matter content of the universe determines its geometry: can we think about a...