Recent content by PeterDonis

Not "wrong", no. It is a valid approximation to GR in the regime where gravity is weak and all relative speeds are small compared to the speed of light. In the sense that we might find some other underlying theory that has these properties, yes. But GR (and a fortiori Newtonian mechanics) will...

More precisely, if we just use the matter we can actually see as the source in the Einstein Field Equation, the model does not match the data. More precisely, they are additional things we add to the source, over and above the matter we can actually see, in order to make the model fit the data...

To follow up more on this: the Ma paper [1] says (bottom of p. 4): It's unfortunate, at least for our discussion here :wink:, that they discard these runs, since that means they don't show data on what the photon 1 and 4 polarizations were. But since it is stated that these are "no swap" runs...

You do get 2, but you can't split the state up into a product of two states each with a value 1 for the number operator. That's what it means for the state to be entangled.

I will note, btw, that although I've pitched this in terms of Bohmian mechanics, what I posted in that post only involves the wave function (which is why I said it was only a sketch, at least as far as the Bohmian model is concerned), so it should be applicable to any QM interpretation--indeed...

I have a suggested Bohmian model of the DCES experiment. I'll sketch it for now, and possibly follow up with more detail in later posts. To be clear about the experimental setup: At the start, we prepare photons A&B in the singlet state ##\Psi^-## (I'll use the standard notation for Bell...

That's correct.

If you're using an interpretation of QM that includes collapse, yes. Paths aren't wave functions, and even in collapse interpretations of QM, they don't collapse, no. Collapse isn't a concept that has any meaning for the individual paths in the path integral.

Not in QM, no. Even that's not quite a direct observable; it gives you the probability amplitude, but all you can actually observe is the squared modulus of that, the probability.

@TheHutch you seem to be trying to model all possible states of light in terms of "photons". Unfortunately, that's not a workable approach. The fundamental object, so to speak, where light is concerned is the quantum electromagnetic field. The term "photon" is much more restricted; it refers...

You're misunderstanding the role the paths play in QM. In QM, all of the paths are included in the machinery that determines the probability amplitudes. You can't pick out just one and ask what its effect is; they're all present in any experiment. The light bending in an inertial elevator...

Are you familiar with the path integral formulation of QM? That is the formulation that uses these paths and explains why.

Yes, that's because QM is not a classical theory. GR is a classical theory. Since, as you note, QM includes non-stationary paths, d'Alembert's principle can't possibly hold for QM. If your question is why that is, the only answer is that, as above, QM is not a classical theory, and it has to...

This is the QM forum, not the relativity forum. If you are asking, what would it mean in the context of quantum field theory in curved spacetime, then we can discuss that in this forum. But I think you need to clarify your question first.

Why do you think this is the case?