【摘要】 设G为n阶简单图,λ2(G)为G的第二大特征根．我们给出了所有使λ2(G)<1 的偶图,以及使λ2(G)<1、围长不小于4的非偶图．更多还原

【Abstract】 Let G be a simple graph with n vertices, and let λ1(G)≥λ2(G)≥…≥λn(G) be the eigenvalues of the adjacency matrix of G. We call λ2(G) the second largest eigenvalue of G. In this paper, all the non-bipartite graphs with girth g≥4 and all the bipartite graphs whose second largest eigenvalue is less than 1 have been determined.更多还原