Madison Chaos and Complex Systems Seminar

Spring 2017 Seminars

All seminars are Tuesday at 12:05 pm in 4274 Chamberlin Hall except as noted. Refreshments will be served.

Short List
Join us for lunch during the summer on the Memorial Union Terrace at noon each Tuesday, starting May 9th!


January 17, 2017

How worried should we be about congenital Zika virus?

Dave O'Connor, UW Department of Pathology and Laboratory Medicine

I will talk about Zika as an example of what happens when a new virus that we know little about emerges, discuss what we've learned about Zika, and then talk about what factors might govern the emergence of such viruses that could threaten human health in the future.

January 24, 2017

The Lyapunov exponent

George Hrabovsky, Madison Area Science and Technology

The Lyapunov exponent is one of the fundamental measures of chaos. What is it? Where does it come from? What does it actually do for us? Can we predict its value? I will explore these ideas in a non-rigorous way.

January 31, 2017

Climate change science, impacts, and mitigation strategies

Susan Nossal, UW Department of Physics

Deep reductions in greenhouse gas emissions are required to avert catastrophic impacts of climate change.  This presentation will briefly overview some of the complexities associated with climate change science and impacts.  One example is the influence on the upper atmosphere of increases in greenhouse gases and of the solar cycle, a major source of natural variability in this region.  The talk will also include discussion of climate change mitigation strategies.

February 7, 2017

Child poverty in the United States

Julia Isaacs, Urban Institute

I will talk about poverty, concentrating on poverty among children.  Who is poor? And how has poverty changed over time? I also will compare child poverty and well-being in the United states with child poverty and well-being in other countries. Finally, I will summarize what is known about the effects of poverty on child development.

February 14, 2017

Functional integration and split in the brain

Shun Sasai, UW Department of Psychiatry

We often engage in two concurrent but unrelated activities, such as driving on a quiet road while talking over the phone. When the conversation is unrelated to driving, how does the brain manage these two concurrent flows? I will present our recent work showing that a brain may functionally split into two separate 'driving' and 'listening' systems when a listening task is unrelated to concurrent driving, but not when the two tasks are related.

February 21, 2017

Nonlinear lives

Robin Chapman, UW Department of Communicative Disorders

Mathematical equations or their visualizations are one way to capture nonlinear trajectories. Poems are another. Three poets who have recently released books of memoir illustrate the devices of metaphor, metonymy, and story that poet use. Robin Chapman will read from Six True Things. Alice D'Alessio will read from Walking the Tracks. Catherine Jagoe will read from Bloodroot.

February 28, 2017

The future of nuclear energy in a carbon constrained world

Mike Corradini, UW Department of Engineering Physics

A study is underway sponsored by the Sloan Foundation investigating the future of nuclear energy. The main goal of the study is to evaluate the prospects for innovative nuclear technologies, policy and business models, and regulatory governance mechanisms to accelerate the transition to a lower-carbon global energy system in the United States and around the world.  The study investigates time periods from the present thru 2050, and the talk will review the major questions being addressed with a special focus on the opportunities presented by considering advanced nuclear technologies to displace fossil fuels.

March 7, 2017

Bach's integration of complexity and simplicity

Trevor Stephenson, Harpsicord

Part of the miracle of Bach’s music is that no matter how contrapuntally layered and complex a piece becomes, the idea and the meaning are never lost. Using several examples from Bach’s The Well-tempered Clavier, I will bring play and discuss how Bach achieves clarity within extremely complex systems. I'll also look at how Bach deals with near-chaotic material, such as the fugue subjects that approach a-tonality; we'd look at how he breaks down a sense of key, and then rebuilds it. I’ll also show how the unique tuning (tempering) method for the The Well-tempered Clavier assists in giving each piece a unique acoustic color. I’ll bring my 17th-century Flemish harpsichord for the presentation.

March 14, 2017

The complexity of the U.S. tax system and the consequences for reform

John Witte, UW La Follette School of Public Affairs

This talk will review the changing status of “tax expenditures” (loopholes) from 1975 to 2015 based on data from a new book by the author.  It will be argued that after a brief respite produced by the 1986 Tax Reform Act, tax expenditures have again grown precipitously to the point that classical tax reform is very improbable. Part of the problem is that tax loophole growth and expansion are a policy mechanism for both political parties and both the legislative and executive branches of government.  Thus, unlike an earlier suggestion by the author for reforming the tax code, he will propose that perhaps it is best now to simply accept tax expenditures as inevitable and try to establish guidelines for which should be supported and which cut back or eliminated.

March 28, 2017

2016 Polling in Nation and State: A scorecard

Charles Franklin, Law and Public Policy and Director of the Marquette University Law School Poll

How did the pre-election polls of 2016, at both national and state levels, perform? What did we learn about the dynamics of the campaign and the issues affecting public polling? How accurate were the polls and were some methods better than others?

April 4, 2017

“Wet chaos”: Characteristics of extreme rains in a changing climate

John Young, UW Department of Atmospheric and Oceanic Science
Edward Lorenz (1917- 2008) produced a series of theoretical papers on the predictability of idealized weather systems which led him to be known as a “Father of Chaos”. He concentrated on weather circulation models which yielded non-periodic behavior. Since “climate” is simply the long-term statistics of weather variability, it also reflects chaos properties which include irregularity of extreme states.

The implication for real weather systems is that precipitation, an important climate variable and by-product of rising moist air, possesses some form of chaos. This is made more complex because precipitating weather releases condensational heating, a positive feedback on the circulation. The properties of chaotic precipitation necessarily depend on the wide varieties space and time scales, ranging from local transient torrential thunderstorms to regional monthly heavy rain totals.

The edges of the attractor basin of precipitation are important because of their impact on ecology and human activities. Examples show how the probability distributions of heavy rain differ greatly from those of temperature, wind, etc. These empirical distributions are uncertain due to limited data length (e.g., 120 years) and improbability of extreme events.  

Some questions of interpretation for power law-like relations and dependence on duration will be discussed.  Finally, the implications of a temperature-dependent water vapor constraint suggest how global warming may lead to increasing limits of extreme precipitation.

April 11, 2017

The influence of spatial connectivity on landscape regime shifts and pattern formation after external pulses

Zak Ratajczak and Paolo D’Odorico, UW Department of Zoology

Ecosystems are often exposed to driver pulses, such as climate oscillations or consumer outbreaks. We currently lack robust theoretical predictions for when a driver pulse will elicit regime shifts, which are instances when an ecosystem no longer recovers to its essential form, functions, and feedbacks. We used a spatially extended vegetation model where increases in grazing pressure can force patches of the landscape to undergo a regime shift from a high productivity state to a self-reinforcing low-productivity state. We considered a factorial combination of driver pulses that increase grazing pressure by differing intensities and for differing durations. These pulses were applied to simulated landscapes with high underlying spatial heterogeneity and differing levels of spatial connectivity between adjacent patches. We considered two scales of resistance to regime shifts: landscape integrity, defined as when >95% of the landscape returned to a high biomass state and refugia potential, defined as the ability to keep >5% of the landscape in the high biomass state. High connectivity landscapes had greater landscape integrity, meaning that they could withstand more intense and longer pulses, and still have a majority of the landscape return to a high biomass state. Low connectivity systems, in contrast, had greater refugia potential, meaning that at least a small portion of the landscape was able to return to a high biomass state, even after more intense or longer pulses. Systems with intermediate connectivity had a more balanced combination of landscape integrity and refugia potential. These landscapes also tended to form coherent spatial patterns after driver pulses that nearly forced a landscape-scale regime shift. Such pattern formation could potentially be used as a warning sign for adaptive management. Ensemble, these simulations suggest that underlying landscape characteristics can greatly alter the landscape and patch-scale potential for regime shifts in response to various external pulses.

April 18, 2017

Life inside the black box: Soil microbes, climate change, and fire

Thea Whitman, UW Department of Soil Science

Although charcoal is renowned for its persistence and stability in soils, it is actually a dynamic and heterogeneous material. Today, pyrolyzed organic matter is important not only in fire-affected ecosystems, but also in managed systems, where it may be produced intentionally as an agricultural soil amendment or for carbon management / climate change mitigation. How soil microbes respond to these inputs is critical for determining the net climate impact, and is only just being revealed, through advances in stable isotope and high-throughput sequencing techniques.

April 25, 2017

Scenarios, simulations, and sustainability science:  Planning for the future of complex systems

Chris Kucharik, UW Nelson Institute

Cleaning up the Yahara lakes is difficult because they are part of a complex system, where the needs of humans and ecosystems compete and long-term challenges, such as climate change and land use planning have many possible consequences and solutions. How can we better prepare for the future given this complexity and uncertainty? We can start with scenarios, or provocative and plausible stories that guide numerical simulations of the future.  Together, these tools can help us understand how our decision-making today could impact our lakes and landscapes in the future. This presentation will cover the process and new model results that are a part of Yahara 2070, a set of scenarios created for the Yahara River watershed by the Water Sustainability and Climate Project at UW-Madison.

May 2, 2017

Year-end celebration

Following the tradition of recent years in which we had a delightful discussion of where we have come and where we might go with the seminars, this last seminar of the semester will be devoted to a continuation of that discussion without any formal speaker. We will also discuss what we want to do during our informal weekly lunches on the Memorial Union Terrace which begin on May 9th. This celebration will include expanded refreshments, to which your own culinary contribution is welcome.