English

Examples of cyclically-interval non-colorable bipartite graphs

Combinatorics 2013-05-30 v1 Discrete Mathematics

Abstract

For an undirected, simple, finite, connected graph GG, we denote by V(G)V(G) and E(G)E(G) the sets of its vertices and edges, respectively. A function φ:E(G){1,2,,t}\varphi:E(G)\rightarrow\{1,2,\ldots,t\} is called a proper edge tt-coloring of a graph GG if adjacent edges are colored differently and each of tt colors is used. An arbitrary nonempty subset of consecutive integers is called an interval. If φ\varphi is a proper edge tt-coloring of a graph GG and xV(G)x\in V(G), then SG(x,φ)S_G(x,\varphi) denotes the set of colors of edges of GG which are incident with xx. A proper edge tt-coloring φ\varphi of a graph GG is called a cyclically-interval tt-coloring if for any xV(G)x\in V(G) at least one of the following two conditions holds: a) SG(x,φ)S_G(x,\varphi) is an interval, b) {1,2,,t}SG(x,φ)\{1,2,\ldots,t\}\setminus S_G(x,\varphi) is an interval. For any tNt\in \mathbb{N}, let Mt\mathfrak{M}_t be the set of graphs for which there exists a cyclically-interval tt-coloring, and let Mt1Mt.\mathfrak{M}\equiv\bigcup_{t\geq1}\mathfrak{M}_t. Examples of bipartite graphs that do not belong to the class M\mathfrak{M} are constructed.

Keywords

Cite

@article{arxiv.1305.6866,
  title  = {Examples of cyclically-interval non-colorable bipartite graphs},
  author = {R. R. Kamalian},
  journal= {arXiv preprint arXiv:1305.6866},
  year   = {2013}
}

Comments

4 pages

R2 v1 2026-06-22T00:24:40.960Z