PeterDonis's latest activity

Yes you can. It applies in whatever region of spacetime is covered by the chart. That's part of the specification of the chart. You're...

What do you mean by this?

First, I'm not sure I see the point of such a restriction, because it rules out practically every scenario where there's any significant...

Who said we were just talking about rotation around the ##z## axis? Non orthogonal components don't contribute to ##L##, but that...

Not in the usual formulation of non-relativistic QM, where a "quantum state" is a ray in Hilbert space, not a vector. Multiplying a...

No, we don't. The fact that ##L = r \times p## does not mean that ##r## and ##p## are orthogonal.

You are misunderstanding something Susskind said, then. Since ##a## is necessarily positive, negative ##\dot{a}/a## would imply negative...

No, the particle can't be at rest because it has nonzero kinetic energy. There is no classical state that corresponds to the ##l = 0##...

The results of using a life jacket or not are well-documented. The lethal consequences have been experienced many, many times, therefore...

You mean https://arxiv.org/abs/2602.07402 (The ABL Rule and the Perils of Post-Selection)? Your formulation sounds like you talked about...

This thread has reached and passed the point of diminishing returns and will remain closed.

Yes, agreed. I think we're saying basically the same thing.

Yes, I've already agreed with that; the only possible topologies are ##S^3## and ##R^3##. The cylinder you describe would be ##S^2...

I'm not sure I agree that there is just one constraint here. First, we have a global topological constraint: the global topology must...

The global topology of maximally extended Schwarzschild spacetime is ##R^2 \times S^2##. The simplest way to see this is to look at a...