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RE: Models, etc.




Can anybody think of a process in nature (excepting quantum mechanical
phenomina) which can be modeled by an equation which is not continuous
and which does not have continuous derivitives of all orders?

1. Magnetisation as a function of applied field below the Curie temperature of
a ferromagnet is continuous but has discontinuous first derivative. Similar
quantities can be found in any first order phase transition.

2. At the liquid-gas critical point, the density as a function of position in
space is fractal. Likewise any system modeled as a fractal will have ill
defined derivatives of something.

Tim Sullivan
sullivan@kenyon.edu