On Clifford's ramification index for Abelian chief factors of finite groups (Q1904237)

As the author states, the ramification index \(e\) which appears in Clifford's theorem concerning the restriction \(V_N\) of an irreducible \(KG\)-module \(V\), where \(N\) is a normal subgroup of a finite group \(G\), is well understood when the field \(K\) is the complex field \(\mathbb{C}\). In his earlier work, the author [Proc. Edinb. Math. Soc., II. Ser. 30, 153-167 (1987; Zbl 0601.20009); ibid. 31, 469-474 (1988; Zbl 0657.20005)] has made some progress in dealing with the case where \(K\) is a finite field and \(G/N\) is cyclic of order \(p^t\), \(p\) prime and \(V_N=eW_1\), with \(W_1\) an irreducible \(KN\)-module. Here, he deals with the more general case `by passing step by step through the chief factors of \(G\) lying above \(N\).' As expected, the results are too technical to be explained in a short review.