Seminar - Katherine Naismith

Extensions of Signed Graphs

Abstract: 

A signed graph is a pair (G, S), where S is a subset of E(G). We can extend a signed graph by adding (i.e. un-deleting) edges, or by splitting vertices (i.e. un-contracting edges). This talk will address two main questions about extensions of signed graphs. The rst is: How can we minimally extend an embedded signed graph so as to "break" its embedding? The second question is related: When does an embedded signed graph extend uniquely? These results represent a step toward a characterization theorem for signed graphs with no odd-K5minor.