Quantum shuffles and quantum supergroups of basic type

Abstract

We initiate the study of several distinguished bases for the positive half of a quantum supergroup $U_q$ associated to a general super Cartan datum $(\mathrm{I},(\cdot ,\cdot ))$ of basic type inside a quantum shuffle superalgebra. The combinatorics of words for an arbitrary total ordering on $\mathrm{I}$ is developed in connection with the root system associated to $\mathrm{I}$. The monomial, Lyndon, and PBW bases of $U_q$ are constructed, and moreover, a direct proof of the orthogonality of the PBW basis is provided within the framework of quantum shuffles. Consequently, the canonical basis is constructed for $U_q$ associated to the standard super Cartan datum of type $\mathfrak{gl}(n|1)$, $\mathfrak{osp}(1|2n)$, or $\mathfrak{osp}(2|2n)$ or an arbitrary non-super Cartan datum. In the non-super case, this refines Leclerc's work and provides a new self-contained construction of canonical bases. The canonical bases of $U_q$, of its polynomial modules, as well as of Kac modules in the case of quantum $\mathfrak{gl}(2|1)$ are explicitly worked out.