kube@cogsci.berkeley.edu (Paul Kube) (05/28/87)
In article <654@pbhyc.UUCP> djo@pbhyc.UUCP (Dan'l Oakes) writes: >In article <19045@ucbvax.BERKELEY.EDU> kube@cogsci.berkeley.edu.UUCP (Paul Kube) writes: > >>As it turns out, relative frequencies of outcomes observed in certain >>experiments violate the inequality. This prima facie shows that >>either there are superluminal signals or there's a strange >>indefiniteness to particle state (coincidentally of the type required >>by a noninstrumentalist interpretation of QM). > >Or that QM is simply inadequate. You've thrown that possibility out the >window unexamined. This shows you haven't understood what I've been saying. That's easy enough to do, so I'll try again: I've been mainly interested in discussing the implications of Bell's inequalities. Far from neglecting the possibility that QM is "simply inadequate", the inequalities *assume* that it is: one of the assumptions in their derivation entails that there are hidden variables not countenanced by QM. And the other assumptions are pretty innocent: that there are no superluminal signals, that probability theory is consistent; stuff like that. Now do the experiments; alas, the inequalilties are violated. So it would seem (assuming the experiments aren't cooked) that either there are superluminal signals, or that there are no hidden variables, or that probability theory is inconsistent. All this without assuming QM is true. (So far I can't see much mathematical arrogance in the argument, no overinterpretation of the formalism. But again, if you can point to some reason for supposing this application of probability theory is infelicitous, do so.) So, no dependence on QM so far. But there are implications for the interpretation of QM. It has always been tempting to interpret QM instrumentally. I take it that you also want to interpret QM instrumentally; your reason seems to be that it's incredibly arrogant to do otherwise, no matter how well confirmed QM is. A more common reason to opt for the instrumental interpretation is that a realistic interpretation requires giving up some cherished conceptual underpinnings of understanding and explanation, viz. determinism and definiteness; these are retained on the hidden-variable interpretation. The importance of the tests of Bell's inequalities is that they apparently remove this reason for wanting an instrumental interpretation of QM, because they show you can't get determinism and definiteness anyway (except at the cost of doing without special relativity). Of course you are still free to opt for an instrumental interpretation, though, again, it would be nice to hear arguments for it (hint: look in Bas C. van Fraasen, _The Scientific Image_). God knows there's too much wrong with QM for it to be right... I will now stop repeating myself. >To say that the mathematics is "inadequate" is not equal to saying that >it "fails to correspond to reality." Newtonian physics corresponds to >reality, within its limits. When applied to relativistic speeds, masses, >etc., however, Newtonian physics becomes inadequate. In what sense does it become inadequate in relativistic applications other than failing to correspond to reality there? >I suggest that something similar is taking place here: that QM corresponds >to reality, within its limits; but that, just as the level of interpretation >and observation once showed Newtonian physics inadequate, so now QM is proving >inadequate under certain conditions. What conditions are these? Its observational adequacy remains unchallenged. If you mean its adequacy for generating understandable explanations---well, the Bell's experiments seem to show we may have to do without that from any observationally adequate theory. --Paul kube@berkeley.edu, ...!ucbvax!kube
ir332@sdcc6.UUCP (05/29/87)
This Bell's inequality sounds most interesting. I for one would
like to see exactly what is derivable from the basic assumptions
already discussed, and how the inequality is tested experimentally.
Anyone got any references to the primary literature handy?
Thanks, Jeff
--
Jeff Miller ARPA: sdcc6!ir332@ucsd.edu
U. C. San Diego (I think)
Dept Psychology, C-009
La Jolla, CA 92093