[IX-103]

Why does pilot wave theory violate locality -- does it assume that the pilot waves travel faster than light? And if so, is it necessary for the pilot waves to travel faster than light or can they be limited to the speed of light and preserve locality?

[marcosdumay]

Pilot wave theory is based on the assumption that every particle is interacting with the entire Universe all the time.

[IX-103]

Does it have to be the simultaneous version of the current universe or can it be the universe as it was distance/c ago?

Actually with relativity and all I'm not exactly sure there is a just a single correct definition of the instantaneous state of the universe.

[aeternus]

Experiments have shown that pilot waves would have to travel faster than the speed of light.

My understanding of the experiment is as follows:

Take two entangled photons, beam them up to satellites far away from each other. The satellites have detectors that measure the polarization angle from 0 to 360 degrees. Since entangled photons have opposite polarization you'd expect an inverted V (red line): https://en.wikipedia.org/wiki/Bell%27s_theorem#/media/File:B...

Instead, you get the blue line. Which is weird, because it is basically a cosine curve, and implies that the photons are able to determine the relative angle of the detectors. The crazy part is that this curve still holds even if those detectors are very far apart and you complete the experiment before any information about the relative angles of the detectors would have time to pass from one detector to the other at the speed of light. This is what implies that a pilot wave would have to move faster than the speed of light.

[pdonis]

> Why does pilot wave theory violate locality -- does it assume that the pilot waves travel faster than light?

Yes. The pilot wave at any given point can be affected instantaneously by changes anywhere else in the universe.

[kgwgk]

But in this regard the pilot wave is not different from the standard Schroedinger’s wavefunction, is it?

[pdonis]

No, it isn't. Both are interpretations of non-relativistic quantum mechanics, and in non-relativistic QM there is no speed of light limit.

[MiroF]

Schroedinger’s wavefunction isn't sufficient in a relativistic context

[kgwgk]

True. To be fair, it's true that the relativistic extensions to Bohmian mechanics are not as advanced as for the "standard" theory. But they are not necessarily impossible and the requirement of a prefered foliation may not be so unacceptable if the history of the universe goes back to a singularity (so there is a "local time since singularity" that gives somes sense to the idea of simultaneity).

[MiroF]

I am not very familiar with Bohmian mechanics/Pilot wave theory, just wanted to make sure what the schro eq is and isn't was clear to everyone