图的广义字典序积的不可收缩性

Unretractive property of generalized lexicographic product of graphs

研究图X与一簇图 { Yx x∈V(X) }的广义字典序积X〔Yx x∈V(X)〕的自同态幺半群 ,得到当所有Yx 的团数都相等时 ,C2n + 1〔Yx x∈V(C2n + 1)〕是不可收缩的当且仅当每一个Yx

Endomorphism monoid of generalized lexicographic product of graphs is discussed.If the clique numbers of all graphs Y x are the same,C 2n+1 〔Y xx∈V( C 2n+1 )〕 is unretractive if and only if every Y x is unretractive.