Heisenberg double H(B^*) as a braided commutative Yetter-Drinfeld module algebra over the Drinfeld double

Abstract: We study the Yetter--Drinfeld D(B)-module algebra structure on the Heisenberg double H(B^*) endowed with a "heterotic" action of the Drinfeld double D(B). This action can be interpreted in the spirit of Lu's description of H(B^*) as a twist of D(B). In terms of the braiding of Yetter--Drinfeld modules, H(B^*) is braided commutative. By the Brzezinski--Militaru theorem, H(B^*)#D(B) is then a Hopf algebroid over H(B^*). For B a particular Taft Hopf algebra at a 2p-th root of unity, the construction is adapted to yield Yetter--Drinfeld module algebras over the 2p^3-dimensional quantum group U_q(sl(2)). In particular, it follows that Mat_p(C) is a braided commutative Yetter--Drinfeld U_q(sl(2))-module algebra and Mat_p(U_q(sl(2))) is a Hopf algebroid over Mat_p(C).