Hebrew University Colloquium Time and Place: Thursday January 3rd, 14:30-15:30, Mathematics Building, Lecture Hall 2 Speaker: Dror Bar Natan (Toronto) Title: Meta-Groups, Meta-Bicrossed-Products, and the Alexander Polynomial Abstract: The a priori expectation of first year elementary school students who were just introduced to the natural numbers, if they would be ready to verbalize it, must be that soon, perhaps by second grade, they'd master the theory and know all there is to know about those numbers. But they would be wrong, for number theory remains a thriving subject, well-connected to practically anything there is out there in mathematics. I was a bit more sophisticated when I first heard of knot theory. My first thought was that it was either trivial or intractable, and most definitely, I wasn't going to learn it is interesting. But it is, and I was wrong, for the reader of knot theory is often lead to the most interesting and beautiful structures in topology, geometry, quantum field theory, and algebra. Today I will talk about just one minor example, mostly having to do with the link to algebra: A straightforward proposal for a group-theoretic invariant of knots fails if one really means groups, but works once generalized to meta-groups (to be defined). We will construct one complicated but elementary meta-group as a meta-bicrossed-product (to be defined), and explain how the resulting invariant is a not-yet-understood yet potentially significant generalization of the Alexander polynomial, while at the same time being a specialization of a somewhat-understood "universal finite type invariant of w-knots" and of an elusive "universal finite type invariant of v-knots". <http://www.math.toronto.edu/~drorbn/Talks/Israel-1301/;> Light refreshments will be served after the colloquium in the faculty lounge at 15:30. YOU ARE CORDIALLY INVITED --------------------------------------------------------- Technion Math Net-2 (TECHMATH2) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Yulia <yulia_g@math.huji.ac.il>