Sheldon Goldstein

[Sheldon Goldstein]

Hi Shan. The crucial point, as you say, is
> physical differences out would require physical differences in.

> But the wave function is a description of the in-between process involving the particles, and it is not necessarily physical or ontological only because the input and output are physical.

Remember that the only noncontroversial difference between the effects of choosing a vs a’ is in the distribution of B’s (collapsed) wave function. If that is not a physical diffference, the game is over and your argument can’t work. And if it is a physical difference the game is also over: you have nonlocality with no need to continue with further hypothetical interactions, nonlinear or otherwise.

Best, Shelly

[Sheldon Goldstein]

Hi Shan. You are right. The proof is too simple. The mistake is this:

One should not take it for granted that the wave function is genuinely
physical, objective, ontic, in the proof of nonlocality. The proof
should depend only on the experimental facts of quantum theory. But for
your proof to work, you must assume that the wave function is ontic.
Otherwise you would not be able to conclude that the hypothetical local
nonlinear evolution of the wave function could lead to physically
different states depending on whether a or a’ had been chosen. Physical
differences out would require physical differences in. (And if a and a’
did directly lead to physically different situations, that would already
constitute nonlocality and you wouldn’t need the hypothetical nonlinear
evolution.)

—
Best, Shelly

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