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Events on Tuesday, April 18th, 2017

Council Meeting
Place: 2314 Chamberlin hall
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Chaos & Complex Systems Seminar
Life inside the black box: Soil microbes, climate change, and fire
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Thea Whitman, UW Department of Soil Science
Abstract: 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.<br>
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.<br>
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. <br>
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.
Host: Clint Sprott
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Theory Seminar (High Energy/Cosmology)
Ubiquity of non-geometry in heterotic string compactifications
Time: 3:30 pm
Place: 5280 Chamberlin
Speaker: Stefano Massai, University of Chicago
Abstract: I will address the problem of classifying supersymmetric string compactifications in regions of moduli space where the supergravity approximation breaks down. I will show evidence that, in the heterotic string, quantum effects generically turns a Calabi-Yau manifold into a T-fold, a non-geometric space defined by T-duality transition functions. I will describe a non-geometric version of ADE singularities, and show a full classification of the six-dimensional super-conformal field theories that describe the low energy physics on such defects.
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