Asymptotics of the Chromatic Index for Multigraphs
β Scribed by Jeff Kahn
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 835 KB
- Volume
- 68
- Category
- Article
- ISSN
- 0095-8956
No coin nor oath required. For personal study only.
β¦ Synopsis
For a multigraph G, let D(G) denote maximum degree and set
We show that the chromatic index /$(G) is asymptotically max[D(G), 1(G)]. The latter is, by a theorem of Edmonds (1965), the fractional chromatic index of G, and the asymptotics established here are part of a conjecture of the author predicting similar agreement of fractional and ordinary chromatic indices for more general hypergraphs. Of particular interest in the present proof is the use of probabilistic ideas and ``hard-core'' distributions to go from fractional to ordinary (integer) colorings.
π SIMILAR VOLUMES
We improve an upper bound for the chromatic index of a multigraph due to Andersen and Gol'dberg. As a corollary w e deduce that if no t w o edges of multiplicity at least t w o in G are adjacent, then ,y'(G) s A ( G ) + 1. In addition w e generalize results concerning the structure of critical graph
We show that coloring the edges of a multigraph G in a particular order often leads to improved upper bounds for the chromatic index Ο (G). Applying this to simple graphs, we significantly generalize recent conditions based on the core of G (i.e., the subgraph of G induced by the vertices of degree
The weak critical graph conjecture [1,7] claims that there exists a constant c > 0 such that every critical multigraph M with at most c β’ β(M ) vertices has odd order. We disprove this conjecture by constructing critical multigraphs of order 20 with maximum degree k for all k β₯ 5.
For a bipartite multigraph, the list chromatic index is equal to the chromatic index (which is, of course, the same as the maximum degree). This generalizes Janssen's result on complete bipartite graphs \(K_{m, n}\) with \(m \neq n\); in the case of \(K_{n, n}\) it answers a question of Dinitz. (The