Combinatorics Seminar- Symmetric Spherical Grids

Speaker: Lowell Abrams, George Washington University
Date and time: Wednesday, October 25, 4-5pm
Place: Rome 771
Title: Symmetric Spherical Grids
Abstract: If an embedding of a graph G in the sphere is a quadrangulation of the sphere, then G is necessarily bipartite. Assuming that G has minimum vertex degree 3 and that all vertices in one block of V(G) have degree 4, we refer to G as a spherical grid. We discuss general structural properties in spherical grids, then use these to completely characterize rotationally symmetric spherical grids having two vertices of degree n, 2n vertices of degree 3, and all other vertices of degree 4. Furthermore, we show how to represent all possible examples as nets. The talk will feature pictures and props.