Abstract
Let Xbe a category with a given(E,M)-factorization structure for morphisms, M ⫆ Mono X. In general, an arbitrary endofunctor T of X fails badly to preserve the E-class. If T carries a monad structure, then T(E) ⫆ E implies that the corresponding category of Eilenberg–Moore-algebras admits (E,M)-factorizations and vice versa. In order to get T as close as possible to this nice algebraic behaviour, a couniversal modification T↪ T with (E) ⫆ E is constructed in two different ways using mild and natural assumptions on E and M, respectively. T inherits its monad structure from T. In case of T = U F, F ⊣ U, the Eilenberg–Moore-category of T contains a universal (E,M-algebraic hull (completion) of U [2, 3]. There are further applications to varietal hulls [4] and to function spaces.
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Richter, G. Coreflectivity of E-Monads and Algebraic Hulls. Applied Categorical Structures 8, 161–173 (2000). https://doi.org/10.1023/A:1008606215120
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DOI: https://doi.org/10.1023/A:1008606215120