q-Witt Algebras, q-Virasoro algebra, q-Lie Algebras, q-Holomorph Structure and Representations

For q generic or a primitive l-th root of unity, q-Witt algebras are described by means of q-divided power algebras. The structure of the universal q-central extension of the q-Witt algebra, the q-Virasoro algebra, is also determined. q-Lie algebras are investigated and the q-PBW theorem for the universal enveloping algebras of q-Lie algebras is proved. A realization of a class of representations of the q-Witt algebras is given. Based on it, the q-holomorph structure for the q-Witt algebras is constructed, which interprets the realization in the context of representation theory.Comment: 18 page

Double-bosonization and Majid's Conjecture, (II): cases of irregular RR-matrices and type-crossings of F4F_4, G2G_2

The purpose of the paper is to build up the related theory of weakly quasitriangular dual pairs suitably for non-standard $R$-matrices (irregular), and establish the generalized double-bosonization construction theorem for irregular $R$, which generalize Majid's results for regular $R$ in \cite{majid1}. As an application, the type-crossing construction for the exceptional quantum groups of types $F_{4}$, $G_{2}$ is obtained. This affirms the Majid's expectation that the tree structure of nodes diagram associated with quantum groups can be grown out of the node corresponding to $U_q(\mathfrak{sl}_2)$ by double-bosonization procedures. Notably from a representation perspective, we find an effective method to get the minimal polynomials for the non-standard $R$-matrices involved.Comment: 42 page

Double-bosonization and Majid's Conjecture, (III): type-crossing and inductions of E6E_6 and E7E_7, E8E_8

Double-bosonization construction in Majid \cite{majid1} is expectedly allowed to generate a tree of quantum groups. Some main branches of the tree in \cite{HH1, HH2} have been depicted how to grow up. This paper continues to elucidate the type-crossing and inductive constructions of exceptional quantum groups of types $E_6$ and $E_7$, $E_8$, respectively, based on the generalized double-bosonization Theorem established in \cite{HH2}. Thus the Majid's expectation for the inductive constructions of $U_q(\mathfrak g)$'s for all finite-dimensional complex simple Lie algebras is completely achieved.Comment: 24 page

Double-bosonization and Majid's Conjecture, (IV): Type-Crossings from AA to BCDBCD

Both in Majid's double-bosonization theory and in Rosso's quantum shuffle theory, the rank-inductive and type-crossing construction for $U_q(\mathfrak g)$'s is still a remaining open question. In this paper, working with Majid's framework, based on our generalized double-bosonization Theorem proved in \cite{HH2}, we further describe explicitly the type-crossing construction of $U_q(\mathfrak g)$'s for $(BCD)_n$ series direct from type $A_{n-1}$ via adding a pair of dual braided groups determined by a pair of $(R, R')$-matrices of type $A$ derived from the respective suitably chosen representations. %which generalize the lower rank cases constructed in \cite{HH1}. Combining with our work in \cite{HH1,HH2,HH3}, this solves Majid's conjecture, that is, any quantum group $U_q(\mathfrak g)$ associated to a simple Lie algebra $\mathfrak g$ can be grown out of $U_q({\mathfrak {sl}}_2)$ inductively by a series of suitably chosen double-bosonization procedures.Comment: 26 pages, 1 figure, Sci. China Ser A (2016) (to appear

Double-bosonization and Majid's conjecture, (I): rank-induction of ABCDABCD

Majid developed in \cite{majid3} his double-bosonization theory to construct $U_q(\mathfrak g)$ and expected to generate inductively not just a line but a tree of quantum groups starting from a node. In this paper, the authors confirm the Majid's first expectation (see p. 178 \cite{majid3}) through giving and verifying the full details of the inductive constructions of $U_q(\mathfrak g)$ for the classical types, i.e., the $ABCD$ series. Some examples in low ranks are given to elucidate that any quantum group of classical type can be constructed from the node corresponding to $U_{q}(\mathfrak{sl}_2)$.Comment: 22 page

Two-parameter Quantum Group of Exceptional Type G_2 and Lusztig's Symmetries

We give the defining structure of two-parameter quantum group of type G_2 defined over a field {\Bbb Q}(r,s) (with r\ne s), and prove the Drinfel'd double structure as its upper and lower triangular parts, extending an earlier result of [BW1] in type A and a recent result of [BGH1] in types B, C, D. We further discuss the Lusztig's Q-isomorphisms from U_{r,s}(G_2) to its associated object U_{s^{-1},r^{-1}}(G_2), which give rise to the usual Lusztig's symmetries defined not only on U_q(G_2) but also on the centralized quantum group U_q^c(G_2) only when r=s^{-1}=q. (This also reflects the distinguishing difference between our newly defined two-parameter object and the standard Drinfel'd-Jimbo quantum groups). Some interesting (r,s)-identities holding in U_{r,s}(G_2) are derived from this discussion.Comment: 34 pages. Pacific J. Math. (to appear in its simplified version

The Green rings of the 2-rank Taft algebra and its two relatives twisted

In the paper, the representation rings (or the Green rings) for a family of Hopf algebras of tame type, the 2-rank Taft algebra (at $q=-1$) and its two relatives twisted by 2-cocycles are explicitly described via a representation theoretic analysis. It turns out that the Green rings can serve to detect effectively the twist-equivalent Hopf algebras here.Comment: J. Algebra (to appear), 34 pages (revised the noncommutativity of Green ring of 2-rank Taft algebra \bar A, rewrote the proofs of Jacobson radicals of the three Green algebras, added some remarks and updated references, etc.

Two-parameter Quantum Affine Algebra of Type Cn(1),{\mathrm C_n^{(1)}}, Drinfeld Realization and Vertex Representation

The two-parameter quantum vertex operator representation of level-one is explicitly constructed for $U_{r,s}(C^{(1)}_n)$ based on its two-parameter Drinfeld realization we give. This construction will degenerate to the one-parameter case due to Jing-Koyama-Misra (\cite{JKM2}) when $rs=1$.Comment: 28 pages. arXiv admin note: text overlap with arXiv:math/9802123 by other author

Universal Central Extensions of the Matrix Leibniz Superalgebras sl(m, n, A)

The universal central extensions and their extension kernels of the matrix Lie superalgebra sl(m, n, A), the Steinberg Lie superalgebra st(m, n, A) in category {\bf SLeib} of Leibniz superalgebras are determined under a weak assumption (compared with \cite{MP}) using the first Hochschild homology and the first cyclic homology group.Comment: 8 pages. Communications in Algebra (to appear

Loewy filtration and quantum de Rham cohomology over quantum divided power algebra

The paper explores the indecomposable submodule structures of quantum divided power algebra $\mathcal{A}_q(n)$ defined in \cite{HU} and its truncated objects $\mathcal{A}_q(n, \bold m)$. An "intertwinedly-lifting" method is established to prove the indecomposability of a module when its socle is non-simple. The Loewy filtrations are described for all homogeneous subspaces $\mathcal{A}^{(s)}_q(n)$ or $\mathcal{A}_q^{(s)}(n, \bold m)$, the Loewy layers and dimensions are determined. The rigidity of these indecomposable modules is proved. An interesting combinatorial identity is derived from our realization model for a class of indecomposable $\mathfrak{u}_q(\mathfrak{sl}_n)$-modules. Meanwhile, the quantum Grassmann algebra $\Omega_q(n)$ over $\mathcal{A}_q(n)$ is constructed, together with the quantum de Rham complex $(\Omega_q(n), d^\bullet)$ via defining the appropriate $q$-differentials, and its subcomplex $(\Omega_q(n,\bold m), d^\bullet)$. For the latter, the corresponding quantum de Rham cohomology modules are decomposed into the direct sum of some sign-trivial $\mathfrak{u}_q(\mathfrak{sl}_n)$-modules.Comment: 26 page