Fuchs' problem for endomorphisms of nonabelian groups

Abstract: In 1960, L\'{a}szl\'{o} Fuchs posed the problem of determining which groups $G$ are realizable as the group of units in some ring $R$. In \cite{chebolu2022fuchs}, we investigated the following variant of Fuchs' problem, for abelian groups: which groups $G$ are realized by a ring $R$ where every group endomorphism of $G$ is induced by a ring endomorphism of $R$? Such groups are called fully realizable. In this paper, we answer the aforementioned question for several families of nonabelian groups: symmetric, dihedral, quaternion, alternating, and simple groups; almost cyclic $p$-groups; and groups whose Sylow $2$-subgroup is either cyclic or normal and abelian. We construct three infinite families of fully realizable nonabelian groups using iterated semidirect products.