Conductor, projectivity and injectivity
Conductor, projectivity and injectivity
Here we discuss the role of the conductor of a ring extension vis-a-vis the descent of projectivity and injectivity.Regarding the former, the first result says that an injective homomorphism of commutative rings descends projectivity if it does so modulo the conductor.The cheap version-that with noetherian hypotheses-of the descent of projectivity …