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10.5 Nonlocalities

The actualisation of propensities is an essentially non-local process. This is because the initial extended field of propensity must act as a whole in order to produce an actual event at a single place, and the choice of one actualising, in order to `block off' all the incompatible possibilities, must be immediately felt in all regions of the potentiality distribution. This `unified action' occurs no matter how widely spread the propensity field may be: it could, for example, be the propensity field of a single photon spread out over many light years in all spherical directions! I explained in chapter 8 how this need not necessarily violate the special theory of relativity. Relativity only limits communications or law-like signals to the speed of light -- it leaves open the possibility that the effects of purely   contingent orderings could be felt simultaneously over large spatial regions.

Although in chapter 9 it was explained that propensities were the underlying `subject' or `matter' of quantum objects, note that, because actualising does not involve the motion of material, propensities are not like `material' spread out. To understand this, we have to change our ideas about matter and its localisation. Strictly speaking, we have to say that a propensity distribution is not actually spread out in space according to its field form, but rather its field distribution describes where it can act in space and time. In an important sense, therefore, propensity fields are non-local objects, at least within the extensions of their own fields. The field distribution behaves like a shadow of an object not in the space of the shadow. The waves of the field distribution are not like waves in water: The wave's oscillatory fluctuations at each point in such a material medium would be only related by causal linking mechanisms, and cannot act as a whole apart from the sequential actions of those mechanisms. An extended water wave cannot, for example, become suddenly localised in a single place.

        Physicists have come to realise increasingly that quantum mechanics is a non-local theory, ever since the significance of the Bell's inequalities has become apparent (see Clauser & Shimony [1978]). Redhead [1987] shows how any realistic extension of quantum mechanics will therefore have to use non-local properties and/or causal connections. He shows that in the propensity interpretation of quantum mechanics, EPR processes violate a `locality principle' which he puts 10.11 in the form  

LOC1: An unsharp value for an observable cannot be changed into a sharp value by measurements performed `at a distance'.
Physicists, however, have not always known how to deal with this fact, largely because they have not had any paradigms to restrict non-local models from completely arbitrariness. There are so many more possibilities for interactions in non-local models compared with local models, that physicists have tended to be bewildered by this new enormous range of possibilities.   Smolin [1986] points out, for example, how the naive application of equipartition in the thermodynamic limit of non-local theories would result in the complete swamping of local interactions by all the many more numerous non-local coupling terms. What we need therefore is a simple paradigm for a nearly-local ontology, so we can begin to make small departures from strict locality without getting lost in science-fiction like realms of speculation. The theory of propensity fields is intended to provide exactly this `minimal' non-locality.  
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Prof Ian Thompson


Author: I.J. Thompson (except as stated)