Generalizing a theorem of P. Hall on finite-by-nilpotent groups

Gustavo Fernandez Alcobér, Marta Morigi

Let ${\gamma }_i(G)$ and $Z_i(G)$ denote the $i$-th terms of the lower and upper central series of a group $G$, respectively. P. Hall showed that if ${\gamma }_{i+1}(G)$ is finite then the index $…