The Genus of Edge Amalgamations of a Type of Graph

Zeling Shao1, Yanpei Liu2, Zhiguo Li1
1Department of Mathematics, Hebei University of Technology, Tianjin 300401, China
2Department of Mathematics, Beijing Jiaotong University, Beijing 100044, China

Abstract

If \( G_1 \) and \( G_2 \) are two graphs, then the edge amalgamation \( G_1 *_e G_2 \) is defined to be the graph obtained by identifying some given edge of \( G_1 \) with some given edge of \( G_2 \). In this paper, it is shown that \( \gamma(G_1 *_e G_2 *_e \ldots *_e G_n) = \lceil \frac{n}{2} \rceil \) where \( G_i \) (\( 1 \leq i \leq n \)) is a critical graph of minimum genus \( 1 \).

Keywords: genus, joint tree, edge amalgamation, orientable surface, embedding