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Anna I. McPherson Lectures
Professor Per Bak
The Niels Bohr Institute
University of Copenhagen
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Who could ever calculate the path of a molecule? How do we know that the
creations of worlds are not determined by falling grains of sand?
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Victor Hugo, Les Miserables
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Public Lecture:
Are worlds determined by grains of sand?
Thursday, October 16th 1997, 20:00
Stephen Leacock Building, Room 132
Abstract:
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Many natural phenomena evolve intermittently rather than following a
smooth gradual path. This "punctuated equilibrium" behaviour indicates
that the underlying dynamics is self-organised critical, with no
characteristic length or time scales. The metaphoric example is a pile
of sand onto which sand is slowly added, resulting in avalanches with a
power law size distribution. Applications from geophysics,
astrophysics, biology, and economics will be presented.
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Science Colloquium:
Learning by Mistake
Friday, October 17th 1997, 16:00
Stephen Leacock Building, Room 026
Abstract:
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A simple model of self-organized learning with no classical (Hebbian)
reinforcement will be presented. Synaptic corrections involved in
mistakes are depressed, i. e. the learning process involves a stick,
but no carrot. The model system operates at a highly adaptive "critical"
state similar to that of recent evolution models. Thus, one might think
of the mechanism as synaptic Darwinism.
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