Madison Chaos and Complex Systems Seminar

Spring 2009 Seminars

All seminars are Tuesday at 12:05 pm in 4274 Chamberlin except as noted.

Short List

Join us for lunch during the summer on the Union Terrace at noon each Tuesday, starting May 12th!

Abstracts

January 20, 2009

Are Americans preparing well (financially) for retirement?

Karl Scholz, UW Department of Economics 

Many people fear that Americans are preparing poorly for retirement. But developing rigorous evidence on this issue is difficult. In this presentation I will briefly discuss the flawed, commonly used, descriptive evidence on the adequacy of retirement wealth accumulation. I will then discuss an alternative strategy for addressing wealth adequacy that makes use of a straightforward, but computationally complex dynamic programming approach that my colleague Ananth Seshadri and I have used (with Surachai Khitatrakun). Our preliminary evidence suggests that only a small fraction of households born before 1954 in a nationally representative data set (the Health and Retirement Study) had net worth below their optimal targets in 2004. I close by offering a few observations given current market upheavals and the unfinished challenges (and need) for translating methodologically complex results into "rules of thumb" that might result in more sensible financial planning advice.



January 27, 2009

Is there a credible upper bound for global sea level rise and can we live with it?
 
Philip Keillor, Association of State Floodplain Managers
 
Do certain aspects of global climate change have a chaotic potential that defies efforts to obtain credible predictability? Take global sea level rise, for instance. Coastal engineers and coastal planners must have a recommended upper bound for sea level rise to be anticipated in this century. However, an IPCC 2007 report stated: “Because understanding of some important effects driving sea level rise is too limited, this report does not assess the likelihood, nor provide a best estimate or an upper bound for sea level rise.” (Synthesis Report, Pg. 7, Section 3. Projected climate change and its impacts. http://www.ipcc.ch/ipccreports/ar4-syr.htm )  Climate change modeler James Hansen is critical of what he calls “scientific reticence” on the subject and called for convening a national panel to address sea level rise (Hansen, J.E. 2007. Scientific reticence and sea level rise. www.iop.org/EJ/article/1748-9326/2/2/024002/erl7_2_024002.html).  In this presentation, the problem of determining a credible upper bound for global sea level rise will be introduced, along with the issues of positive and negative feedbacks, climate surprises, and tipping points that challenge the predictability of sea level rise.  The Association of State Floodplain Managers (ASFPM) is engaged in a conversation with the U.S. Army Corps of Engineers over interim guidelines for sea level rise in this century.

This talk is available in PowerPoint format at http://sprott.physics.wisc.edu/Chaos-Complexity/keillor.ppt.


 
February 3, 2009

Norepinephrine, networks, and behavior: One aproach to systems neuroscience

David Devilbiss, UW Department of Psychology

Norepinephrine, an endogenous chemical within the brain modulates target neuron excitability.  This neuromodulator permits global state changes of the brain (from sleep to waking) as well as participating in brain functions including cognitive processes such as attention and dysfunctions such as attention deficit hyperactivity disorder and depression. This talk will describe the nonlinear nature of this neuromodulators effects on target neuron discharge properties, the summation of its effects on many individual neurons to alter the dynamics of neuronal populations, and the resultant effects on animal behaviors.



February 10, 2009

A brief survey of financial derivatives

Don Hester, UW Department of Economics

Financial derivative contracts have exploded in varietyand complexity since the early 1970s. I will describe and interpret the basic "plain vanilla" derivatives, forward, futures, and option contracts, in the first half of this talk. Then I will explore the reasons for the proliferation of new derivatives, interpret several of them, and comment on how they have impacted the economy.



February 17, 2009

A fractal view of the world

Clint Sprott, UW Department of Physics

Since the time of the ancient Greek philosophers, we have been taught that the geometry of lines and surfaces and solids is the proper description of the world. Recently, a new type of geometry has emerged in which the fundamental objects are "fractals." Fractals have non-integer dimension and self-similar structure on all scales. Natural objects such as rivers, mountains, clouds, snowflakes, trees, plants, and landscapes are best described by fractal geometry. Examples of fractals will be shown, and methods will be described whereby you can generate fractal patterns on your computer and analyze their properties.
 
This talk is available as a PowerPoint Presentation.
This talk uses computer animations from the Chaos Demonstrations program.



February 24, 2009

Studying dynamical systems with computer algebra systems

George Hrabovsky, Madison Area Science and Technology

Computer algebra systems are powerful programming platforms that allow a single programmer to complete, in a week, what would normally take a team of programmers months to do. In this talk I will demonstrate, through a variety of examples, how these tools can make mathematical explorations of dynamical systems much simpler and in many ways more powerfully than traditional, strictly numerical approaches.



March 3, 2009

Place; It’s complicated: Nagas in the Himalaya
 
Chris Limburg, UW Department of Geography
 
Place is more complex than we think it is.  Places—so often taken for granted—shape our environment, society, and imagination.  This talk will elaborate the ways that we think about places.  It will address questions like: what is a place, exactly?  How does thinking about places help us understand our world?  And: isn’t place just a location in inert space?  In answering these questions, I will argue for the importance of using place as a lens as well as a site.  Examining place epistemologically and ontologically, this talk will demonstrate the usefulness of thinking geographically about our fragmented relationship with the environment.  With a deeper sense of place we can engage environment, society, and self as emergent despite their seeming fixity.  The talk will first outline the debates concerning the nature of place in geography.  Then it will use the example of naga nature spirits in the Kathmandu valley to illustrate the complexity of place.



March 10, 2009

Engaging the flow: a creative dialogue revisited

Harry Webne-Behrman, UW Office of Human Resource Development
 
Creative conversations don’t mechanically follow ‘outline form,’ they emerge from the synergies and interactions of participants in hard-to-predict ways. Is there a way to facilitate such dialogues, rather than direct them, so 1 + 1 >2? Is there a way to capture the creative ideas that emerge? Last Fall, the Chaos & Complexity Seminar engaged in a creative dialogue around a broad question with some productive ideas. On this occasion, the group is asked to focus more deeply on one of the issues that emerged from the previous dialogue:
 
“How might UW-Madison best engage its resources to meet the challenge of assuring the “Wisconsin Experience” for its students?”
 
The Wisconsin Experience is intended to result in graduates who have the capacity and commitment to make the world a better place. It is intended to build upon the unique strengths of the UW-Madison community to foster such ideals that have resulted in extraordinary citizens, global activists and volunteers, corporate leaders and others with a special sense of social responsibility and an activated, current sense of the Wisconsin Idea.
 
My intention in this dialogue is to gain participant reflections on this initiative in its pedagogical, research, service, and cultural dimensions. What aspects of this Experience are worth pursuing? Where should resources be emphasized and how might they best be organized to do so?
 
For additional information about this important initiative from Aaron Brower (Vice-Provost for Teaching and Learning) and Lori Berquam (Dean of Students), please visit: http://www.learning.wisc.edu  -- a summary of the objectives of the Wisconsin Experience is attached, as well. Join us for fascinating conversation and see what happens!



March 24, 2009
 
Dynamics of the white pine blister rust pathogen on wild gooseberry hosts
 
Maria Newcomb, UW Department of Plant Pathology

The reductionist scientific approach has often been followed to increase our understanding of minimally- and intensively-managed systems for purposes of making informed management decisions.  My doctoral research is on the dynamics of a host-pathogen interaction in a minimally-managed woodland system.  This and other pathosystems could potentially be described as complex, chaotic, and/or poorly understood.   I will present results from observational and manipulative studies on the interaction between a rust pathogen and its gooseberry hosts.  Our hope is that results of individual experiments can be combined to build a better understanding of the whole system to better inform management decisions.  We also recognize that features of complex and chaotic systems may either limit our abilities to put the parts together to understand the whole, or at least challenge us to interpret the combined results carefully.  At the end of the talk I will invite the audience to participate in a discussion about the benefits and limitations of the reductionist experimental approach in complex plant-pathogen systems.



March 31, 2009

The origins of emergent behavior in bacterial communities
 
Douglas B. Weibel, UW Department of Biochemistry
 
Bacteria sense surfaces and undergo physiological changes, which programs their growth and motility and coordinates their behavior. The resulting bacterial communities display ‘emergent’ properties in which the coordination of the behavior of cells is not predictable from the sum of the individual components (e.g. cells). The resulting structures behave as multicellular organisms and collectively colonize niches in search of nutrients and other growth factors. The transition of a group of ‘individual’ bacterial cells to collective, multicellular behavior is accompanied by the upregulation of pathogenic factors, suggesting that in this state the organisms are preparing to invade a host. An understanding of the mechanisms that control and regulate the switch from individual behavior to multicellular behavior will identify mechanisms and targets that may play a role in preventing and treating microbial pathogenesis.
 
We are particularly fascinated by the mechanisms that cells use to coordinate their movement on surfaces. In contrast to our understanding of the biophysics involved in the motility of bacterial cells (e.g. Escherichia coli) in bulk fluids, almost nothing is known about the mechanisms that play a role in cell motility on surfaces. We are exploring two physical mechanisms that may play a role in the coordination of cellular movement on surfaces based on: i) physical interactions between cells mediated by bundling between flagella on adjacent cells; and ii) physical interactions between cells in close proximity to each other that are produced by the disturbance in the local fluid field by the rotation of the cells during motility. In this talk I present recent work from our group on both mechanisms and demonstrate that bacterial ‘swarming’ may be one of the most tractable experimental systems for identifying the mechanisms that drive systems toward emergent behavior. These experiments may shed light on systems that extend far beyond microbial systems, and include financial markets, weather, and population dynamics.



April 7, 2009

A search for the simplest chaotic partial differential equation

Charlie Brummitt, UW Department of Physics

A search for the simplest chaotic partial differential equation (PDE) concludes that the Kuramoto-Sivashinsky equation is likely the simplest chaotic PDE. We enumerate all of the equations with one quadratic or cubic nonlinearity that are "simpler" than the Kuramoto-Sivashinsky equation and test them for chaos, but none appear to be chaotic. Nevertheless, the search finds a strikingly simple PDE that is chaotic in the discrete limit of finitely many, coupled ordinary differential equations (ODEs). Analysis of this finite system indicates why the chaos vanishes in the limit of infinitely many ODEs.



April 14, 2009

Taking the pulse of the geodynamo

Brad S. Singer, UW  Department of Geoscience

During the past 2.6 million years Earth's outer core geodynamo has produced at least 18 geomagnetic excursions and 5 full polarity reversals.  This record has been compiled from terrestrial volcanic rocks, including mainly basaltic lava flow sequences, but also two silicic ash beds, that have been analyzed using modern paleomagnetic techniques and dated using the 40Ar/39Ar variant of the K-Ar radio-isotopic clock.  Several brief periods of field instability associated with excursions correlate with lows in paleointensity or directional changes recorded globally in marine sediments that are dated using astronomically-forced oxygen isotope signals or ice layer-counting. However, the lack of correlation of several excursions between marine and terrestrial records indicates that neither sediments, nor lava flows, are ideal recording media.  Another factor complicating correlation is that some excursions may be geographically localized and not expressed globally.  Despite decades of observation, these records remain fragmentary, especially when periods of millions of years are considered.  Recent 40Ar/39Ar dating in our laboratory, that includes age determinations for the Mono Lake, Laschamp, Blake, Pringle Falls, Big Lost, West Eifel excursions, as well as the Halawa (C2r.2r-1) cryptochron, prompt us to critically review the terrestrial record of geodynamo instability and propose a Geomagnetic Instability Time Scale (GITS) for the Quaternary period.  Both the ca. 4:1 ratio of excursions to reversals during the past 2.6 Ma as well as the temporal pattern of occurrence of these events provide fundamental input as to the long‑term behavior and, possibly, the structure of the core dynamo.  On the one hand, intervals of significant temporal clustering of excursions have highlighted a relatively stable period of high field strength lasting >250,000 years in the middle of the Brunhes chron during which time few, or no, excursions took place.  On the other hand, successive paleomagnetic excursion records may be critical in regard to understanding the behaviors and interactions between the mantle‑influenced field source in the shallow core (the hypothesized SCOR‑field) and the deeper‑held source of the axial dipole.  If in fact a successful reversal attempt requires the axial dipole field source to be weakened below some threshold strength for substantial duration (ca. 10,000 ‑20,000 years), times of grouped excursions may also be the most probable times for a change in polarity.



April 21, 2009

Metabolic tales: Saga of human drug metabolism and metabolic imprinting

Olga Trubetskoy, UW Departments of Pharmacy and Comparative Biosciences

Drug metabolizing enzymes are considered to be a weapon in a war of eaten versus eater (or plant-animal warfare) evolved to detoxify and quickly eliminate potent plant toxins from the animal organisms. This highly complex and coordinated system of enzymes and drug transporters is unique for each organism and its overall response is determined by a combination of genetic and epigenetic factors and can be also influenced by changes in the environment.
 
I am going to present a series of “Metabolic Tales” about correlation and co-evolution of changes in the human drug metabolizing system with nutritional, therapeutic, behavioral, social and environmental changes happening in a modern human society both locally and globally. Some of the questions I will try to raise are:
 
- What defines our personal and environmental “metabolic signature” in a context of a personal “metabolic tale”?  What does it tell about our genetically “pre-recorded” or imprinted interactions with environment? To what degree changes in your personal metabolic signature can affect and cause environmental changes? Can you change your personal “metabolic record” similar to changing your carbon footprints? What happens to our metabolic signature if our environment changes?  To what degree we can serve as our own sensors of future environmental changes?



April 28, 2009

Applications of neural networks in time-series analysis

Adam Maus, UW Department of Computer Science

Artificial neural networks are mathematical models that emulate biological neural systems.  They have been used in classification, pattern recognition, and time-series analysis.  In time-series analysis, neural networks can be used for forecasting but also to determine how many and which past values are required to predict the future.  Determination of this 'lag space' sheds light on the nature of the dynamics and permits development of minimal models capable of replicating the dynamics. I will highlight applications of neural networks in the real world as models that classify, forecast, and analyze data while emphasizing their use in determining the lag space.

This talk is available as a PowerPoint  Presentation.



May 5, 2009

Earthquakes beneath the sea: Understanding the mechanics of fault zones through subsurface imaging and scientific drilling

Harold Tobin, UW Department of Geology and Geophysics

Understanding of the processes by which earthquakes occur remains one of the great challenges of geophysics. The complex interplay among frictional processes, stress, pore fluid pressure, temperature, and other factors means that a comprehensive model for fault physics has not been achieved. One reason for this is the lack of in situ observations and samples from within the faults deep beneath the earth's surface. To address this problem, several major projects have been launched to drill into fault zones. The massive subduction earthquakes which occur at the boundary between two tectonic plates at subduction zones are especially of interest because they cause devastating tsunami, and occur with repeating characteristics. Off the Pacific coast of Japan, the NanTroSEIZE (Nankai Trough Seismogenic Zone Experiment) project targets a subduction zone for drilling to sample and place instruments into and around the fault zone responsible for these tsunami-generating earthquakes. Three-dimensional seismic reflection surveys image the plate boundary zone and provide evidence for fault properties. Drilling provides evidence on the rock composition, chemistry, stress, and other parameters. These unique new datasets are helping to test theoretical and laboratory-derived models for fault physics. I will discuss the overall challenge and present results from the first phase of drilling in 2007-2008.