$M$-subgroups and normal-subgroup lattices of finite groups

Annesh Nag, Pronay Biswas, Amartya Goswami

Let $G$ be a group. A normal subgroup $E$ is an $M$-subgroup if $E\cap N_1\cap N_2\ne 1$ whenever $N_1\cap N_2$, $E\cap N_1$, and $E\cap N_2$ are non-trivial for normal subgroups $…