11/03/2005, 16:30 — 17:30 — Amphitheatre Pa2, Mathematics Building
João Faria Martins, Instituto Superior Técnico
Categorical Groups, Knots and Knotted SurfacesWe define an invariant of knots and an invariant of knotted surfaces from any finite categorical group (crossed module of groups). We illustrate its non-triviality by calculating an explicit example, namely the Spun Trefoil. The talk will be based on:
 João Faria Martins, Categorical Groups, Knots and Knotted Surfaces.