Fall semester in full swing, we resume our lunchtime seminar series.

The first meeting of the seminar is, as usual, in **Grainger Library**, *room 335*.

We start the semester with talks by *Bruce Reznick*, Math, talking on Non-negative polynomials and sums of squares in theory and (theoretically) in practice,

We will talk about real polynomials in many variable with the

property that they only take non-negative values; obvious candidates are

sums of squares of real polynomials, but these aren’t enough. The subject

ties in with Hilbert’s 17th Problem and semidefinite programming. There

will be lots of examples.

*David Lebauer*, Energy Biosciences Institute, reporting on What we know and what we don't know about ecosystems.

Our objective is to quantify and predict ecosystem functions such as crop production, pollution control, and water use. We use Bayesian meta-analysis and data assimilation to synthesize heterogeneous data and knowledge. Mechanistic ecosystem models are used

to scale across data collected from different scales and resolutions. This talk will describe some of the methods we use to quantify what we know and identify gaps in our knowledge that can be addressed through data collection and model development. The result

is more comprehensive and precise ecological forecasts and reanalysis.

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