Published online by Cambridge University Press: 22 January 2016
In this paper we prove the fundamental exact sequence in (co)homology for non-normal subgroups announced in our previous note [8]: Let H be a subgroup of a group G. If M is a G-module and if, for a natural number n, Hm(U, M) = 0 for m = 1, …, n - 1 and for every subgroup U of H which is an intersection of conjugates of H in G, then we have an exact sequence
the significance of the maps and the group Hn(H, M, M)1 will be explained below. (We have a dual result for cohomology groups).