Dear Topologists and Friends of Topology,
Elena will give the topology seminar tomorrow (Thursday).
Title: Oriented matroids and straight-edge embeddings of graphs
Abstract: Matroid theory is an abstract theory of dependence
introduced by Whitney in 1935. It is a natural generalization of
linear (in)dependence. Oriented matroids can be thought of as
combinatorial abstractions of point configurations over the reals. To
every linear (straight-edge) embedding of a graph one can associate an
oriented matroid, and the oriented matroid captures enough information
to determine which pairs of disjoint cycles in the embedded graph are
linked. In this talk, we will introduce the basics of oriented
matroids. Then we will discuss results about the type and number of
links in linear embeddings of $K_9$, the complete graph on nine
vertices, and in linear embeddings of the complete 3-partite graph
$K_{3,3,1}$. This is joint work with Ramin Naimi.