Monday, March 23, 2009

Physics and Complexity

A wonderful article on another aspect of "many-body" interaction dealing with complexity when a lot of interactions are involved. While this isn't exactly on the same issue as the emergent phenomena that have been mentioned by physicists such as Robert Laughlin and Phil Anderson, it is nonetheless quite interesting and have similar philosophical foundation.

As noted earlier, the systems of interest are ‘many-body’, made up of many (N >> 1) similar individual units, with the concern the co-operative behaviour of the whole. The descriptor ‘complex’ is used to describe collective behaviour that cannot be anticipated simply from the properties of isolated individual units or from interactions among only a few of them, but arises from conflicts when large numbers of individuals have mutually incompletely satisfiable few-body rules, a feature known as ‘frustration’; indeed complex cooperative behaviour can arise with even very simple individual units and very simple interactions. Among the consequences of this frustration and the resultant compromise are that optima and equilibrium are difficult to achieve and that responses to perturbations are slow, in part extremely so, and often chaotic.

Not exactly the emergent phenomena in condensed matter, but still another aspect in which knowledge at the individual particle level cannot predict the outcome.


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