Abstract

A chordal graph is the intersection graph of a family of subtrees of a host tree. In this paper we generalize this. A graph G=(V,E) has an (h,s,t)-representation if there exists a host tree T of maximum degree at most h, and a family of subtrees S_{v vV} of T, all of maximum degree at most s, such that uvE if and only if |S_u∩S_v|t. For given h,s, and t, there exist infinitely many forbidden induced subgraphs for the class of (h,s,t)-graphs. On the other hand, for fixed hs3, every graph is an (h,s,t)-graph provided that we take t large enough. Under certain conditions representations of larger graphs can be obtained from those of smaller ones by amalgamation procedures. Other representability and non-representability results are presented as well.

Keywords: Intersection graph; Tolerance; Chordal graph; k-simplicial vertex; Subtree representation; Regular tree

Article Outline

1. Introduction

2. Preliminaries

3. Chordal graphs

4. Representability

5. Amalgamation

6. Non-representability

7. The case of complete bipartite graphs

References