COLORING DECOMPOSITIONS OF COMPLETE GEOMETRIC GRAPHS

A decomposition of a non-empty simple graph G is a pair [G, P] such that P is a set of non-empty induced subgraphs of G, and every edge of Gbelongs to exactly one subgraph in P. The chromatic index chi'([G, P]) of a decomposition [G, P] is the smallest number k for which there exists a k-coloring of the elements of P in such a way that for every element of P all of its edges have the same color, and if two members of P share at least one vertex, then they havedifferent colors. A long standing conjecture of Erdos-Faber-Lovasz states that every decomposition [K-n, P] of the complete graph K-n satisfies chi'([K-n, P]) <= n. In this paper we work with geometric graphs, and inspired by this formulation of the conjecture, we introduce the concept of chromatic index of a decomposition of the complete geometric graph. We present bounds for the chromatic index of several types of decompositions when the vertices of the graph are in general position. We also consider the particular case when the vertices are in convex position and present bounds for the chromatic index of a few types of decompositions.