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Decomposing \(\lambda K_{v}\), into the Graphs with Seven Vertices, Seven Edges and one 5-Cycle for any Index \(\lambda\)

Yanfang Zhang1, Qingde Kang2
1College of Mathematics and Statistics Hebei University of Economics and Business Shijiazhuang 050061, P.R. Chi
2Institute of Mathematics, Hebei Normal University Shijiazhuang 050016, P.R. China

Abstract

Let \(\lambda K_{v}\) be the complete multigraph of order \(v\) and index \(\lambda\), where any two distinct vertices \(x\) and \(y\) are joined exactly by \(\lambda\) edges \(\{x,y\}\). Let \(G\) be a finite simple graph. A \(G\)-design of \(\lambda K_{v}\), denoted by \((v, G, \lambda)\)-GD, is a pair \((X, \mathcal{B})\), where \(X\) is the vertex set of \(K_v\) and \(\mathcal{B}\) is a collection of subgraphs of \(K_{v}\), called blocks, such that each block is isomorphic to \(G\) and any two distinct vertices in \(K_{v}\) are joined in exactly \(\lambda\) blocks of \(\mathcal{B}\). There are four graphs with seven vertices, seven edges, and one 5-cycle, denoted by \(G_i\), \(i=1,2,3,4\). In \cite{9}, we have solved the existence problems of \((v, G_i, 1)\)-GD. In this paper, we obtain the existence spectrum of \((v, G_i, \lambda)\)-GD for any index \(\lambda\).

Keywords: G-design, G-holey design, G-incomplete design.