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(i) You seem to be saying that the final state in my model should simply be “the evolving state of psi in”. But this is not the case. Even in standard QM, the final state is the collapsed psi after measurement. In both standard Bohm theory and in my retrocausal version, the final state is that branch of the initial wavefunction that the particle actually follows after this wavefunction is spatially split by the measurement interaction, with the empty branches being deleted. Hence, in every theory, the final wavefunction is quite independent of the initial one (i.e., it is a different vector in Hilbert space) and is determined by either the particle’s hidden position, or by conditions further in the future, or by nothing at all, depending on which theory we use.
(ii) The fact that my theory reduces back to the standard Bohm model in the usual situation where the future measurement result is not yet known was meant to be established by the short proof in Sec. 5 of my new paper (i.e., it is shown that the 4-current density becomes identical and so the velocity and probability density will too). If you are not happy with this proof, please let me know.
(iii) Concerning Bell’s nonlocality, I thought it was generally accepted that this nonlocal effect cannot be explained within the standard Bohm model without using a preferred reference frame. So when I said “two boundary conditions are needed in this picture”, I was trying to say that it does not seem to be possible to achieve Lorentz invariance within a Bohmian framework without introducing a final boundary condition.