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Stream: learning: questions

Topic: morphisms of monads and Kleisli categories


view this post on Zulip Paolo Perrone (Jan 20 2022 at 15:43):

It is well known that there is a bijection between morphisms of monads and (backward) functors between the Eilenberg-Moore categories commuting with the forgetful functors.
Is a similar statement known for Kleisli categories, does anyone know?

view this post on Zulip Nathanael Arkor (Jan 20 2022 at 16:27):

Yes. Monads morphisms are in bijection with functors between Kleisli categories commuting with the inclusion functors.

view this post on Zulip Nathanael Arkor (Jan 20 2022 at 16:27):

It's formally dual to the statement about EM categories.

view this post on Zulip Nathanael Arkor (Jan 20 2022 at 16:29):

The earliest reference is most likely Maranda's On fundamental constructions and adjoint functors, though it's also implicit in Linton's work.

view this post on Zulip Oscar Cunningham (Jan 20 2022 at 16:46):

BY 'inclusion' functors here do you mean the free functors? I think that's what it would be if it was dual to the EM result.

view this post on Zulip Nathanael Arkor (Jan 20 2022 at 16:53):

The functors CKl(T)\mathbf C \to \mathbf{Kl}(T) into the Kleisli categories, yes.

view this post on Zulip Paolo Perrone (Jan 21 2022 at 09:03):

Thank you!