The bichromaticity of a bipartite graph B is defined as the maximum value of r + s for which B has the complete bipartite graph K,, as a homomorphic image We determine the bichromaticity of any bipartite cylinder graph C2,, x P, or torus graph CZn x C , , In the process, w e disprove a conjecture of
Bichromaticity of bipartite graphs
β Scribed by Dan Pritikin
- Publisher
- John Wiley and Sons
- Year
- 1985
- Tongue
- English
- Weight
- 312 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
β¦ Synopsis
Let 8 be a bipartite graph with edge set β¬and vertex bipartition M, N.
The bichromaticity p ( 6) is defined as the maximum number p such that a complete bipartite graph on p vertices is obtainable from 5 by a sequence of identifications of vertices of M or vertices of N. Let p = max{lMI, IN}. Harary, Hsu, and Miller proved that P(8) 2 p + 1 and that p(T) = p + 1 for Tan arbitrary tree. We prove that P(B) I p + l β¬ / / p yielding a simpler proof that p(T) = p + 1. We also characterize graphs for which KP.2 is obtainable by such identifications. For OK, the graph of the K-dimensional cube, we obtain the inequality 2K-' + 2tlog2 ' J 9 ( w ) = W ' .
π SIMILAR VOLUMES
For two integers a and b, we say that a bipartite graph G admits an (a, b)bipartition if G has a bipartition (X, Y ) such that |X| = a and |Y | = b. We say that two bipartite graphs G and H are compatible if, for some integers a and b, both G and H admit (a, b)-bipartitions. In this paper, we prove
## Abstract Matrix symmetrization and several related problems have an extensive literature, with a recurring ambiguity regarding their complexity and relation to graph isomorphism. We present a short survey of these problems to clarify their status. In particular, we recall results from the litera