cianfa72's latest activity

For your first assumption, that's true. For your second assumption, that the topology allows for a global inertial chart, why do you...

On a second thought, I believe my post #19 isn't entirely correct. For a given spacetime, assume there exists a Lorentzian frame field...

Another point related to post #18. For a given spacetime suppose there is a set of 4 (algebraically) independent vector fields of...

When discussing isometric embeddings, there is a little more to it. The metric of the submanifold is taken to be induced from the...

As far as I can tell, by picking a pointwise non-orthogonal basis vector fields (one timelike and three spacelike) with constant...

Ok, so your "therefore" should not have been there.

Right, the latter is unrelated to the former. I just restated the conditions @Ibix put forward in post #10.

Ah yes. The definition of frame field/tetrad/vierbein requires pointwise mutual orthogonality of frame's vectors fields evaluated at any...

But your argument was you can’t embed a plane in e.g. a 3 sphere because the plane has zero curvature and the sectional curvature in...

Can we extend the construction given in #11 to any spacetime, e.g. even to non maximally symmetric spacetimes ? I'm not positive about...

So for instance in Minkowski spacetime that has 10 independent symmetries, pick 4 independent translational KVFs (they define a frame...

Ok, since assuming isotropic laws includes the light propagation process. Isotropy forces Einstein synchronization, i.e. spacelike...

Ok. That would rule out e.g. the coordinate transform ##x'=log(x)## because an object with no proper acceleration moving in the x'...

Ok, you mean that the requirement that zero proper acceleration has constant coordinate speed allows for spatial planes (spacelike...

I had a DM with @PAllen about the notion of non-standard inertial frame. Let's consider a (global) inertial frame in the context of...