MIT Combinatorics Seminar

On the freeness of truncated affine Weyl arrangements

Masahiko Yoshinaga  (RIMS, Kyoto, Japan)

Friday, October 22, 2004    4:15 pm    Room 2-338


Freeness of a hyperplane arrangement is defined algebraically using module of derivations. And it has an interesting combinatorial property: Terao's factorization theorem for characteristic polynomial. I will talk about the freeness of extended Catalan/Shi arrangements and its combinatorial corollaries. In the proof, I will discuss a characterization for freeness.

And a possible relation between algebraic properties of the derivation module and combinatorics of characteristic polynomial, such as ``positions of zeros'', will also be discussed.