Reply To: God knows where all the particles are!


Looking back, I find my initial statement not so bad as a summary. In this exchange I did not see any argument suggesting that Bohmian trajectories should be taken more seriously than a fairy tale. Inventing some idle wheels for a theory and claiming that these now make the theory more realistic is diametrically opposed to what I would call realistic. The main differences are hence in the views about what science should be. These differences
were indeed further clarified in our exchange, and that is what I will be taking home.

Here are some items that came up in the exchange that may be worth thinking about for a Bohmian.
(1) From Rainer Plaga’s question: What happens in a Bohmian mixed state preparation, when none of the apparatus basis states have “forever disjoint” position supports? Then even if the particle is dynamically decoupled, none of its effective wave functions will satisfy the Schrödinger eq. So this idea of making a wave function for a subsystem by plugging in the real value Y for the apparatus may cause more problems than it solves.

(2) About fuzzy assumptions: I think it is not correct to say that everything is in two simple equations, which essentially need no further interpretation. When it comes to analyzing anything concrete experiments much more has to be brought in. If you want, you can think of operational QM as a pragmatic way of organizing this additional information, including standing assumptions about fixed measurement results. BM needs these too, but has to express them, much less transparently, in terms of many-body apparatus wave functions. This is the place where everything becomes hazy, very much in-principle, and a little bit dishonest.

(3) The idea of De-Bohmification: This is a simple substitution test. Use the current treatment of “unreal” variables like spin and apply it to some of the positions. This new theory, except for the slightly artificial real/unreal distinction, has exactly the same arguments going for it as BM. Try to honestly answer the question whether you would notice the difference. Travis found the idea of doing without the trajectories “crazy”. But is it any more crazy than just forgetting about the ether?

Anyway, thanks for participating.
So long, Reinhard

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