Chaos and Complex Systems Seminar
Spring 1996 Seminars
Dates, speakers, titles and abstracts will be listed as they become
Tentatively, meetings will be noon Tuesdays in 4274 Chamberlin Hall.
- 30 January. Self-organizational
- 6 February. Fred Brauer: ``Recruitment
Group and Its Effect on the Spread of a Sexually Transmitted
- 13 February. Jude W. Shavlik:
Agents that Learn from Reinforcements''
- 20 February. W. Davis Dechert:
Exponents in Reconstructed Dynamics.''
- 27 Feburary. Kevin Mirus: ``Effects of
on Nonlinear Systems.''
- 5 March. Sean B. Carroll: `` Development
of Butterfly Wing Patterns.''
- 12 March. Spring break --- no seminar
- 19 March. Robert L. Wilson: ``Iterated
- 26 March. John Anderson: ``The Solution
Processing Problems Using Genetic Programming Techniques.''
- 2 April. Michael Bleicher: ``A Model for
Programs? --- Symmetry across the Curriculum.''
- 9 April. Clint Sprott: ``Is It Noise, or
- 16 April. David Griffeath:
Random Cellular Automata'' in B231 Van Vleck
- 23 April. Kellie Evans: ``Larger than
- 30 April. Cosma Shalizi: ``Is the
Done Yet? Quantifying Self-Organization, Especially in Cellular
- 7 May. Troy Shinbrot: ``Something for
Role of Voids in Granular Convection.''
30 January. Self-organizational meeting
Hopefully short. Bring ideas for possible speakers. We will also be
whether to make the seminars less formal and more interactive.
6 February. Fred Brauer, UW Mathematics.
into a Core Group and Its Effect on the Spread of a Sexually
Abstract: In models for the transmission of a sexually
disease it is natural to separate the population into groups with
levels of sexual activity and to concentrate on a core group of
active individuals. We begin with an extremely simple model in which
the core members are sexually active, but there is a rate of
of new members into the core which depends on the prevalence of
among core members. It is possible to have an unstable endemic
with slow oscillations of large amplitude for the infective
If we refine the model by including sexual activity among non-core
as well, counter-intuitive behavior is possible. For example, an
in the rate of activity by non-core members may stabilize the system
reduce the prevalence of infection. It is not proposed to use this
to control the spread of sexually transmitted diseases.
13 February. Jude W. Shavlik, UW Computer
``Providing Advice to Agents that Learn from Reinforcements.''
Abstract: Learning from reinforcements is a promising
creating intelligent agents. However, this style of machine learning
requires a large number of training episodes. We present an approach
addresses this shortcoming by allowing a reinforcement learner to
advice given, at any time and in a natural manner, by an external
In our approach, the (human) advice-giver watches the learner and
makes suggestions, expressed as instructions in a simple programming
Based on techniques from knowledge-based neural networks, these
are inserted directly into the agent's "utility function." The
not be perfectly correct nor complete; subsequent learning further
and refines the advice. We present empirical evidence that shows our
leads to statistically-significant gains in performance.
advice improves the learner regardless of the stage of training at
it is given.
20 February. W. Davis Dechert, Department of
University of Houston. ``Spurious Lyapunov Exponents in
Abstract: One method that has been used to calculate the
exponents from the data of an unknown dynamical system has been to
a functional form to the data, and then calculate the Lyapunov
from the fitted function. Because of their universality, neural
are used to represent the dynamical system. In this talk we show
the problems that can occur with this method, and in particular how
largest Lyapunov exponent can be miscalculated in this way.
27 February. Kevin Mirus, UW Physics.
Periodic Perturbations on Nonlinear Systems.''
Abstract: Several methods for controlling chaotic behavior
been developed over the last few years. One technique that can be
to effect the dynamics of a nonlinear system is to drive
system parameter. This technique has been implemented numerically
a wide range of perturbation amplitudes and frequencies on several
systems, including the logistic equation, the Lorenz equations, the
equations, and coupled map lattices. Cases have been found in which
chaotic behavior can be eliminated at certain perturbation
with very small amplitude perturbations, but the overall occurence
solutions is not greatly diminished.
5 March. Sean B. Carroll, Howard Hughes
UW. ``Development and Evolution of Butterfly Wing Patterns.''
Abstract: How do new features evolve? How does natural
act upon animal patterns? Butterfly wings are exceptional in the
and diversity of their color patterns. I will discuss genetic and
aspects of wing patterns and the modification of developmental
12 March. Spring break --- no seminar
19 March. Robert L. Wilson, UW Mathematics.
Abstract: Iterated Function Systems (IFS) have achieved fame
a beautiful picture of a fern, as well as applications in various
Commercially this technology is being used for image compression. An
is abstractly a collection of functions which map a space into
with restrictions on the space and on how the functions move points
Applied repeatedly, in a deterministic or a random way, the
have a fixed set which acts as an attractor. We will skim lightly
the terminology and a minimum of necessary theoretical background,
on algorithms to implement an IFS, examples showing how those
correspond to pictures, and how an algorithm can be used to encode a
26 March. John Anderson, UW Atmospheric
Solution of Signal Processing Problems Using Genetic Programming
Abstract: Difficult non-linear optimization problems arise in
common signal processing estimation procedures. In many cases the
of large numbers of local minima and the very small convergence
the global minimum result in a problem which is essentially
to solve without resorting to suboptimal approximations of the
problem. Koza and others have shown Genetic Programming (GP) methods
perform remarkably well on a number of highly non-linear estimation
including symbolic regression so it is natural to investigate their
in this problem domain. I will present results for two very
quite difficult problems, ARMA spectral estimation, and the design
filters for unequal sample spacings. In each case the GP approach is
to yield usable solutions to problems which are resistant to
techniques. These problems will also be used to study the effects of
selection algorithms on the solution efficiency.
2 April. Michael Bleicher, UW Mathematics.
for Interdisciplinary Programs? --- Symmetry across the
Abstract: A group of faculty from four different colleges,
over ten departments is working together to create a course on
in its various aspects and uses.
This first course currently under construction is for
students. It is anticipated it will be a ``Quantitative-B'' course
lower division students. It will be modularized, so that given
can be used in other courses in the various departments, as
will be a heavy use of computer visualization in each of the
is hoped that these modules will be prepared for dissemination and
use on the World Wide Web.
A panel of the participating faculty will discuss both the nature
the content of the course modules and also the computer
This first course is looked at as a first step toward two future
The first is more advanced and more specialized courses on the
The second is development of a program in computer
9 April. Clint Sprott, UW
It Noise, or Is It Chaos?''
Abstract: Many quantities in nature fluctuate in time.
are the stock market, the weather, seismic waves, sunspots,
and plant and animal populations. New tests are being developed to
whether such fluctuations are random or whether they are examples of
chaos, in which case there may be a simple underlying cause. If
of chaos is found, it may be possible to improve the short-term
Methods for distinguishing chaos from noise will be described, and
will be shown.
Griffeath, UW Mathematics. ``Self-Organization of Random
Unusual Place: Room B231 Van Vleck hall, usual time.
Abstract: We will illustrate some contemporary themes in
study of cellular automaton (CA) dynamics that form patterns
disorder. The presentation will combine colorful real-time
demos with a tour of CA resources available on the Web.
Evans, UW Mathematics. ``Larger than Life.''
Abstract: Larger than Life (LtL) is a four-parameter family
automata that generalizes John Conway's celebrated Game of Life.
"movies" will demonstrate the diverse forms of self-organization
by the LtL family. Various rigorous and empirical results will be
Shalizi, UW Physics. ``Is the Primordial Soup Done Yet?
Self-Organization, Especially in Cellular Automata.''
Abstract: Most decisions about whether something is
or not are made at an intuitive, ``I know it when I see it'' level.
talk will explain why this is unsatisfactory, describe some possible
measures of self-organization from statistical mechanics and from
theory, and test them on several different cellular automata whose
or lack thereof, is not in dispute.
7 May. Troy Shinbrot, Department of Chemical
Northwestern University. ``Something for Nothing: The Role of
Abstract: The onset and various aspects of fully developed
convection in vibrated containers can be captured by an analysis of
of voids. Predictions for convective onset as a function of system
are developed and tested with existing data. Voids --- and how they
filled --- provide a stochastic model to mimic fully developed
convection. It is found that the vertical flow field depends on the
cosine of the horizontal coordinate and on a mixed
of the vertical coordinate. Companion, model-based, numerical
validate the theoretical predictions. Independent full soft-particle
provide an independent check of the predictions of the theory.
Up to the Chaos and Complex Systems Seminar
(Sun Apr 14 16:35:10 CDT 1996)