Hopf monads are identified with monads in the 2-category Opmon of monoidal categories, opmonoidal functors and transformations. Using Eilenberg-Moore objects, it is shown that for a Hopf monad $S$, the categories Alg(Coalg($S$)) and Coalg(Alg($S$)) are canonically isomorphic. The monadic arrows Opmon are then characterized. Finally, the theory of multicategories and a generalization of structure and semantics are used to identify the categories of algebras of Hopf monads.
Theory and Applications of Categories, Vol. 10, 2002, No. 19, pp 469-485 http://www.tac.mta.ca/tac/volumes/10/19/10-19.dvi http://www.tac.mta.ca/tac/volumes/10/19/10-19.ps http://www.tac.mta.ca/tac/volumes/10/19/10-19.pdf ftp://ftp.tac.mta.ca/pub/tac/html/volumes/10/19/10-19.dvi ftp://ftp.tac.mta.ca/pub/tac/html/volumes/10/19/10-19.psTAC Home