No Arabic abstract
We rederive a popular nonsemisimple fusion algebra in the braided context, from a Nichols algebra. Together with the decomposition that we find for the product of simple Yetter-Drinfeld modules, this strongly suggests that the relevant Nichols algebra furnishes an equivalence with the triplet W-algebra in the (p,1) logarithmic models of conformal field theory. For this, the category of Yetter-Drinfeld modules is to be regarded as an textit{entwined} category (the one with monodromy, but not with braiding).
Let $(R^{vee},R)$ be a dual pair of Hopf algebras in the category of Yetter-Drinfeld modules over a Hopf algebra $H$ with bijective antipode. We show that there is a braided monoidal isomorphism between rational left Yetter-Drinfeld modules over the bosonizations of $R$ and of $R^{vee}$, respectively. As an application of this very general category isomorphism we obtain a natural proof of the existence of reflections of Nichols algebras of semisimple Yetter-Drinfeld modules over $H$. Key words: Hopf algebras, quantum groups, Weyl groupoid
Given a Hopf algebra $H$ and a projection $Hto A$ to a Hopf subalgebra, we construct a Hopf algebra $r(H)$, called the partial dualization of $H$, with a projection to the Hopf algebra dual to $A$. This construction provides powerful techniques in the general setting of braided monoidal categories. The construction comprises in particular the reflections of generalized quantum groups, arxiv:1111.4673 . We prove a braided equivalence between the Yetter-Drinfeld modules over a Hopf algebra and its partial dualization.
For a Hopf algebra B with bijective antipode, we show that the Heisenberg double H(B^*) is a braided commutative Yetter--Drinfeld module algebra over the Drinfeld double D(B). The braiding structure allows generalizing H(B^*) = B^{*cop}braid B to Heisenberg n-tuples and chains ...braid B^{*cop}braid B braid B^{*cop}braid Bbraid..., all of which are Yetter--Drinfeld D(B)-module algebras. 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_qsl(2).
We describe a Nichols-algebra-motivated construction of an octuplet chiral algebra that is a W_3-counterpart of the triplet algebra of (p,1) logarithmic models of two-dimensional conformal field theory.
Haisheng Li showed that given a module (W,Y_W(cdot,x)) for a vertex algebra (V,Y(cdot,x)), one can obtain a new V-module W^{Delta} = (W,Y_W(Delta(x)cdot,x)) if Delta(x) satisfies certain natural conditions. Li presented a collection of such Delta-operators for V=L(k,0) (a vertex operator algebra associated with an affine Lie algebras, k a positive integer). In this paper, for each irreducible L(k,0)-module W, we find a highest weight vector of W^{Delta} when Delta is associated with a miniscule coweight. From this we completely determine the action of these Delta-operators on the set of isomorphism equivalence classes of L(k,0)-modules.