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| Self-Organized Criticality | |
In 1991, a researcher in the
School of Physics expanded the theory of self-organized criticality, which he and his colleagues
originated in 1987 while at Brookhaven National Laboratory.
The theory asserts that complex systems far from equilibrium
spontaneously evolve toward a critical state without external
tuning. The best-known example involves sandpiles that gradually
reach a critical state — leading to avalanches of varying sizes
— as grains of sand are slowly added. The work and its
implications remain controversial in the physics community.
Proponents of self-organized criticality believe it may
explain many extraordinary or unstable phenomena, including
earthquakes, stock prices, electrical flow, fluctuating river
levels, traffic jams, quasar signals and even the presence of
fractal shapes in nature.
The 1991 research on self-organized criticality was published
in Physical Review Letters by Georgia Tech physicist Dr. Kurt
Wiesenfeld, Dr. James Theiler of MIT's Lincoln Laboratory and Dr.
Bruce McNamara of Reed College. The original theory was described
by Wiesenfeld, Per Bak and Chao Tang of Brookhaven.
In 1997, Dr. Peter Jung, a visiting physicist at Georgia Tech,
and Dr. Ann Cornell-Bell of Connecticut-based Viatech Imaging
found the first evidence that chemical activity within networks
of brain cells displays behavior characteristic of self-organized
criticality. While the implications of the work remain unclear,
the researchers believe further study could lead to new insights
into disease processes, improved techniques
for diagnosing diseases of the brain, and
perhaps even new treatment options.
Also, one of Wiesenfeld's former Ph.D. students, Jeff Hasty
(now at Boston University) did his dissertation on a new theory
of self-organized criticality using an idea known as "the
Renormalization Group." It aims to explain the origin of
self-organized critical behavior from first principles, which are
fundamental tenets that do not invoke (as most theories do)
unproven hypotheses.
That work was published in Physical Review
Letters in 1998. Meanwhile, Wiesenfeld's work on self-organized
criticality is continuing, now with a focus on magnetic
avalanches in superconductors.
Georgia Tech file photo
The theory of self-organized criticality, developed in part
by physics professor Dr. Kurt Wiesenfeld, finds its best-known
example in sandpiles, which gradually reach a critical state —
leading to avalanches of varying sizes — as grains of sand are
slowly added.
For more information, contact Dr. Kurt Wiesenfeld, School of Physics,
Georgia Tech, Atlanta, GA 30332-0430. (Telephone: 404-894-2429) (E-mail:
kurt.wiesenfeld@physics.gatech.edu)
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