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Events on Tuesday, March 11th, 2014

Chaos & Complex Systems Seminar
Variability, uncertainty, and vulnerability in our chaotic climate
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: John Young, UW Department of Atmospheric and Oceanic Sciences
Abstract: Climate and weather are part of a chaotic continuum which impact our world through variability, predictive and statistical uncertainty, and damaging extremes. In this talk I will illustrate these issues with examples from observed atmospheric temperature and precipitation patterns and time behavior.

Weather chaos naturally extends to slow variations and often power-law spectra. The probability distributions of temperature differ strongly from those for precipitation, which yield power law distributions at the extreme range. Impacts often result from extreme states which exceed threshold values. Since extremes are typically estimated with large uncertainty, ecological impacts are similarly estimated for a finite range of probability. An example of a physical constraint on extreme precipitation will be given: the "1,000 year flooding rain".
Host: Clint Sprott
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Faculty Candidate Seminar
Photonic topological insulators and pseudomagnetism
Time: 4:00 pm
Place: 4274 Chamberlin Hall
Speaker: Mikael Rechtsman, Technion - Israel Institute of Technology,
Abstract: I will present two examples in which aEuro~fictitious fieldsaEuroTM lead to surprising photonic effects that would be difficult (if not impossible) to achieve with real fields. Firstly, I will present the first observation of the topological protection of light - a aEuro~Photonic Floquet Topological InsulatoraEuroTM [1]. The structure is an array of coupled helical waveguides (the helicity generates a fictitious circularly-polarized electric field that leads to the TI behavior). Second, I will demonstrate artificial magnetic fields (aEuro~pseudomagnetismaEuroTM) in photonic lattices [2]. The pseudomagnetic field is generated by inhomogeneously straining the system (thus breaking periodicity), and leads to photonic Landau levels with very high photonic density of states. Potential applications include robust photonic devices and strong light-matter interaction over large areas.

[1] Rechtsman, M. C. et al. Nature 496, 196aEuro"200 (2013).

[2] Rechtsman, M. C. et al. Nature Photon. 7, 153aEuro"158 (2013).
Host: Thad Walker/Sue Coppersmith
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