15:45
The asymptotic geometry of mapping class groups and application
Abstract
I shall describe the asymptotic geometry of the mapping class
group, in particular its tree-graded structure and
its equivariant embedding in a product of trees.
This can be applied to study homomorphisms into mapping class
groups defined on groups with property (T) and on lattices in semisimple groups.
The talk is based upon two joint works with J. Behrstock, Sh. Mozes and M. Sapir.
Anthony Lock and Becky Shipley
Abstract
Anthony Lock will speak on "A Column Model of Moist Convection".
Universal moduli of parabolic bundles on stable curves
Abstract
A parabolic bundle on a marked curve is a vector bundle with extra structure (a flag) in each of the fibres over the marked points, together with data corresponding to a choice of stability condition Parabolic bundles are natural generalisations of vector bundles when the base comes with a marking (for example, they partially generalise the Narasimhan-Seshadri correspondence between representations of the fundamental group and semistable vector bundles), but they also play an important role in the study of pure sheaves on nodal curves (which are needed to compactify moduli of vector bundles on stable curves). Consider the following moduli problem: pairs $(C,E)$ of smooth marked curves $C$
and semistable parabolic bundles $E\rightarrow C$. I will sketch a construction of projective moduli spaces which compactify the above moduli problem over the space of stable curves. I'll discuss further questions of interest, including strategies for understanding the cohomology of these moduli spaces, generalisations of the construction to higher-dimensional base schemes, and possible connections with Torelli theorems for parabolic vector bundles on marked curves.
15:45