Search Talks

A very close supernova explosion could have caused a mass extinction

of life in Earth. In 1996, Brian Fields, the late Dave Schramm and the
speaker proposed looking for unstable isotopes such as Iron 60 that could
have been deposited by a recent nearby supernova explosion. A group from
the Technical University of Munich has discovered Iron 60 in deep-ocean
sediments and ferromanganese crusts due to one or more supernovae that
exploded O(100) parsecs away about 2.5 million years ago. These results
have recently been confirmed by a group from the Australian National
University, and the Munich group has also discovered supernova Iron 60 in
lunar rock samples and in microfossils of magnetotactic bacteria. 
This colloquium will discuss the data and their interpretation
in terms of supernova models, and the possible implications for
life on Earth.

Representations of the fundamental groups of surfaces appear so often in geometry that it's tempting to see them primarily as geometric structures. In recent years, however, researchers have uncovered beautiful new features of these representations by thinking of them instead as dynamical systems. As an invitation to the dynamical point of view, I'll describe how geometric tools from the study of billiards can be used to build invariants of surface group representations.

Confomal transformations and conformal algebras in D=2 Recap Lecture Six