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This Week at Physics

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Events on Tuesday, November 13th, 2012

Chaos & Complex Systems Seminar
Role of biofuels in meeting our future energy demands
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Natalie Hunt, UW Department of Forest Ecology and Management
Abstract: The Renewable Fuels Standards (RFS) set out in the 2007 Energy Independence and Security Act call for an increase in the use of renewable transportation fuels to 36 billion gallons per year by the year 2022. In order to meet these standards, there will be increased demand for cellulosic feedstocks such as agricultural residues and dedicated bioenergy crops. This could result in increased production intensity on existing cropland or expansion of production into environmentally sensitive lands, which will impact soil carbon and nutrient content of agricultural soils. Some of the major questions surrounding biofuels feedstock production include what the long-term impacts of these changed production practices on soil fertility will be and whether or not farmers are willing to manage their land for bioenergy feedstocks. There is much uncertainty around the complex interactions among biophysical crop characteristics, agronomic practices, and the socioeconomic factors of the farmers who will manage the bioenergy feedstocks. The research of these system intersections will determine the role of biofuels in meeting our future energy demands.
Host: Sprott
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Theory Seminar (High Energy/Cosmology)
Cosmological Perturbations: Isocurvature, Vorticity and Magnetic Fields
Time: 4:00 pm
Place: 5280 Chamberlin
Speaker: Adam Christopherson, University of Nottingham
Abstract: In this talk I will discuss some recent, complementary work that I have undertaken using cosmological perturbation theory, a powerful technique for modeling inhomogeneities in the universe. After a brief review of the basics, I introduce isocurvature, or non-adiabatic pressure perturbations, and calculate their spectrum in the settings of standard, concordance cosmology, and inflationary models involving two scalar fields. I then extend the discussion beyond linear perturbations, and show that vorticity can be sourced at second order with only scalar perturbations, the source term being quadratic in the gradients of first order energy density and non-adiabatic pressure perturbations. I present a first estimate of this vorticity's power spectrum, and highlight some potential observational consequences. One of these is the possible sourcing of sizeable magnetic fields, and I briefly sketch some current work on including magnetic fields in perturbation theory in a consistent way. I close with some ideas for future work.
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