Caterpillar tolerance representations of graphs

Glenn E Faubert, University of Rhode Island

Abstract

A caterpillar, H, is a tree containing a path, P, such that every vertex of H is either in P or adjacent to P. Given a graph G, a caterpillar tolerance representation of tolerance t on a caterpillar H, is a mapping of each vertex v ∈ V(G) to a subtree H_v ⊆ H, such that uv ∈ E( G) if and only if H_u and H _v share at least t vertices. ^ Denote by cat[h,t] the set of all graphs for which there exists a tolerance t representation of G in a caterpillar of maximum degree h. Given any positive integers, h and t, it is determined for all values of n whether or not a caterpillar tolerance representations exists for a cycle of length n using a representing caterpillar of maximum degree h and tolerance t. ^ We show equivalence among various classes including cat[3,1] = cat[h,1] = cat[3,2] for h ≥ 3 and cat[4,2] = cat[3,3]. Also, for h ≥ 5 we show that cat[h,2] ⊊︀ cat[h − 1,3]. ^ A vertex, v, in a graph, G, is called simplicial if the set of neighbors of v induces a clique in G. We say that a graph G has an asimplicial asteroidal triple if there exists in G three distinct vertices v₁, v₂,v₃, none of which are simplicial, and such that for all permutations i, j, k of the indices 1,2,3 there exits a v_iv_j path which is distance at least two from v_k. We provide the characterization of cat[3,1] as the set of all chordal graphs that do not contain an asimplicial asteroidal triple. And since cat[3,1] = cat[h,1] = cat[3,2] for h ≥ 3, we get characterizations for them as well. ^

Subject Area

Mathematics

Recommended Citation

Glenn E Faubert, "Caterpillar tolerance representations of graphs" (2005). Dissertations and Master's Theses (Campus Access). Paper AAI3186904.
http://digitalcommons.uri.edu/dissertations/AAI3186904

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