Reply To: Retrocausal Bohm Model

[Nathan Argaman]

Hello Aurelian and Rod,

Thanks very much for your replies.

I will need to take a look at the papers of Miller and of Aharonov and Gruss.

The way I see it, it is completely OK for the Born rule to be stipulated, rather than derived. Newton also stipulated the universal law of gravitation, even though he disliked the idea of action at a distance. Of course, having a derivation from some “basic” physical principles is nice, but it is not strictly required.

What I was looking for a few years ago, as Ken Wharton also was and still is, is a reformulation of QM in terms of exclusively local beables. We know from Bell’s theorem that such a formulation must be retrocausal. The non-local wavefunction can then be understood as an epistemic tool, and it cannot affect the “paths of the particles” or whatever the ontic variables may be. Needless to say, such a formulation has not been found yet.

My paper on this was published in 2010, and is available in
http://scitation.aip.org/content/aapt/journal/ajp/78/10/10.1119/1.3456564
and in
http://arxiv.org/abs/0807.2041
(I thought you would see that I linked to it in my contribution to this conference). I was able to include a simplistic retrocausal toy model in it, designed to be as simplistic as the nonlocal toy model which Bell himself included in his original paper. You will not find a derivation of Born’s rule there, or anything as general as that, but it seems that it is the earliest place in which one can find an explicit retrocausal model which reproduces Bell-type correlations in terms of only local beables.

In the discussion, I wanted to compare with other retrocausal models, and I cited your model but did not include it in the comparison because it did not provide a different route to obtaining the probabilities of the measurement outcomes. In this sense it is similar not only to Aharonov et al, but also to the Transactional Interpretation, which uses the same math, but nevertheless introduces the novel concept of retrocausality.

Thanks again, Nathan.