A simplification functor for coalgebras

For an arbitrary-type functor F , the notion of split coalgebras, that is, coalgebras for which the canonical projections onto the simple factor split, generalizes the well-known notion ofsimple coalgebras. In case F weakly preserves kernels, the passage from a coalgebra to its simple factor is functorial. This is the simplification functor . It is left adjoint to theinclusion of the subcategory of simple coalgebras into the category S e t F of F -coalgebras, making it an epireflective one. If a product of split coalgebras exists, then this is split and preserved by the simplification functor. Inparticular, if a product of simple coalgebras exists, this is simple too.