A note on separable functors and monads with an application to equivariant derived categories

Abstract

For an adjoint pair \((F, U)\) of functors, we prove that \(U\) is a separable functor if and only if the defined monad is separable and the associated comparison functor is an equivalence up to retracts. In this case, under an idempotent completeness condition, the adjoint pair \((F, U)\) is monadic. This applies to the comparison between the derived category of the category of equivariant objects in an abelian category and the category of equivariant objects in the derived category of the abelian category.