An extension of Zassenhaus' theorem on endomorphism rings
An extension of Zassenhaus' theorem on endomorphism rings
Let $R$ be a ring with identity such that $R^{+}$, the additive group of $R$, is torsion-free. If there is some $R$-module $M$ such that $R\subseteq M\subseteq\mathbb{Q}R\ (=\mathbb{Q}\otimes_{\mathbb{Z}}R)$ and ${\rm End}_{\mathbb{Z} }(M)=R$, we call $R$