Some \(k\)-fold Edge-graceful Labelings of \((p, p-1)\)-graphs

W. C. Shiut1, Sin-Min Lee 2, Karl Schaffer3
1Department of Mathematics Hong Kong Baptist University 224 Waterloo Road, Kowloon Tong Hong Kong, China.
2Department of Mathematics and Computer Science San José State University One Washington Square, San José, CA 95192-0108, U.S.A.
3Department of Mathematics De Anza College Cupertino, CA 95014, U.S.A.

Abstract

An edge-graceful \((p, q)\)-graph \(G = (V, E)\) is a graph with \(p\) vertices and \(q\) edges for which there is a bijection \(f : E \to \{1,2,\ldots,q\}\) such that the induced mapping \(f^+ : V \to \mathbb{Z}_p\), defined by \(f^+(u) \equiv \sum\limits_{uv \in E} f(uv) \pmod{p}\), for \(u \in V\), is a bijection. In this paper, some results on edge-gracefulness of trees are extended to \(k\)-fold graphs based on graphs with \(p$ vertices and \(p – 1\) edges. A \(k\)-fold multigraph \(G[k]\) derived from a graph \(G\) is one in which each edge of \(G\) has been replaced by \(k\) parallel edges with the same vertices as the original edge. Certain classes of \(k\)-fold multigraphs derived from paths, combs, and spiders are shown to be edge-graceful, as well as other graphs constructed by combining these graphs in specified ways.