A note on injectivity of monomial algebras
We show that a monomial algebra $Λ$ over an algebraically closed field $K$ is self-injective if and only if each map $\mathrm{soc}(_ΛΛ)\to \ _ΛΛ$ can be extended to an endomorphism of $_ΛΛ$, and provide a complete classification of such algebras. As a consequence, we show that the class of self-injective monomial algebras is a subclass of Nakayama algebras.