Forbidden Subgraphs for Hamiltonicity of 1-Tough Graphs

Abstract

A graph G is said to be 1-tough if for every vertex cut S of G, the number of components of G − S does not exceed |S|. Being 1-tough is an obvious necessary condition for a graph to be hamiltonian, but it is not sufficient in general. We study the problem of characterizing all graphs H such that every 1-tough H-free graph is hamiltonian. We almost obtain a complete solution to this problem, leaving H = K1 ∪ P4 as the only open case.

Keywords

• forbidden subgraph
• 1-tough graph
• h-free graph
• hamiltonian graph