As of May 9 - May 11,  2001

Noetherian Ring Seminar
Topic: Graph Homomorphisms and Coloring
Presenter: Karen L. Collins, Wesleyan University
Date: Wednesday, May 9, 2001, Time: 4:30 p.m., Location: Fine Hall 322
Abstract: A graph homomorphism F: G -> H is a map between the vertices of graphs G and H which preserves the edges of G: that is, if u~v in G, then F(u)~F(v)  in H.  Any coloring of H pulls back to a coloring of G, hence the chromatic number of G is less than or equal to the chromatic number of H.  We will discuss the relationship between graph homomorphism and graph coloring, and the No-Homomorphism Lemma.

Graduate Student Seminar
Topic: The Nilpotent Variety in its Natural Setting
Presenter: Julianna Tymoczko, Princeton University
Date: Friday, May 11, 2001, Time: 1:30 p.m., Location: Fine Hall 214
Abstact: The nilpotent variety lies at the crossroads of many different mathematical paths, including geometry, representation theory, combinatorics, even numerical analysis.  It is defined as follows: first, a flag in an n-dimensional complex vector space V is a nested collection of vector subspaces $V_1 \subseteq V_2 \subseteq\ldots \subseteq V_n = V$ -- namely, a line contained in a plane contained in a three-dimensional subspace contained in a ...  Given a nilpotent operator N, the collection of flags whose subspaces are each preserved by the action of N, so that $N V_i \subseteq V_i$ for each i, is called the nilpotent variety.  We will provide an introduction to this and certain closely related varieties, placing them in their context and, if time permits, discussing some recent results.

Geometry Seminar
Topic:  Equivariant de Rham torsions
Presenter: Sebastian Goette, Tuebingen
Date:  Friday, May 11, 2001, Time:  4:00 pm,  Location:  Fine Hall 314