Reply To: The Merits of the de Broglie-Bohm Theory

Robert Griffiths

Dear Jean,

My critique of Bohmian mechanics (BM) was posted in the Why Bohmian Tbeory
thread begun by Shelly, and you might want to take a look at it. A key problem
is that Bohmian trajectories can give the wrong answer, at least from the
perspective of an experimentalist who doesn’t like to be told that his detector
was triggered by a particle passing a meter away.

Nonlocality in the sense of instantaneous nonlocal dynamical influences (to be
distinguished from nonlocal correlations, which are also present in classical
physics) is a serious problem for BM. There is no experimental evidence for
such influences, as shown by the fact that even those who believe in them agree
that they cannot carry information. The supposed indirect evidence based on
violations of Bell inequalities can be countered by noting the derivation of
such inequalities employs hidden variables which are treated classically (they
commute). See my “Quantum Locality,” Found. Phys. 41 (2011) 705;
arXiv:0908.2914. Nonlocality is also a serious problem when it comes to
constructing a satisfactory relativistic version of BM–a problem which Bell
(in his ‘Against Measurement’) regarded as an important unfinished task. So
far as I know, it remains unfinished.

I will grant you the clarity of Bohmian mechanics. But by itself that does not
make it a good theory of the quantum world.

Bob Griffiths

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