设H为有限群G的一个子群。称H在G中是s-半正规的,若对任意的素数p||G|,只要(p,|H|)=1,就有PH=HP,其中P∈Sylp(G);称H在G中是c-可补的,若存在G的子群N,使得G=HN且H∩N≤HG=CoreG(H)。证明了下面定理 设F是一个包含超可解群类U的饱和群系,H△G,且G/H∈F。则G∈F,若下列条件之一成立:(1)若H的每个Sylow子群的所有极大子群在G中或者s-半正规或者c-可补;(2)若F^*(H)的每个Sylow子群的所有极大子群在G中或者s-半正规或者c-可补,其中F^*(H)是H的广义Fitting子群。该定理统一了最近的一些结果。
A subgroup H of a finite group G is called s - seminormal in G if it permuts with every Sylow p - subgroup of G with(p, |H| ) = 1 ;a subgroup H of a finite group G is said to be c - supplemented in G if there exists a subgroup N of G such that and HAN≤HG = CoreG(H). In this paper we prove following:Theorem Let F be a saturated formation containing U, the class of all supersolvable groups and G a group with a normal subgroup H such that G/ H ∈ F. Then G ∈ F if one of following holds : ( 1 ) all maximal subgroups of any Sylow subgroup of H are either s - seminormal or c - supplemented in; ( 2 ) all maximal subgroups of all Sylow subgroups of F ^* ( H), the generalized Fitting Subgroup of H,are either s -seminormal or c -supplemented in G. This unifies some recent results.