The space of surface shapes, and some applications to biology

The problem of comparing the shapes of different surfaces turns up in different guises in numerous fields. I will discuss a way to put a metric on the space of smooth Riemannian 2-spheres (i.e. shapes) that allows for comparing their geometric similarity. The metric is based on a distortion energy defined on the space of conformal mappings between a pair of spheres. I'll also discuss a related idea based on hyperbolic orbifold metrics. I will present results of experiments on applying these techniques to biological data. This involves comparing the similarity of surfaces obtained from collections of teeth, bones and brain cortices. This is joint work with Patrice Koehl.