The quotient of a Kauffman bracket skein algebra by the square of an augmentation ideal

Abstract

We give an explicit basis $\mathcal{B}$ of the quotient of the Kauffman bracket skein algebra $\mathcal{S} (\Sigma)$ on a surface $\Sigma$ by the square of an augmentation ideal. As an application, it induces two kinds of finite type invariants of links in a handle body in the sense of Le. Moreover, we construct an embedding of the mapping class group of a compact connected surface of genus $0$ into the Kauffman bracket skein algebra on the surface completed with respect to a filtration coming from the augmentation ideal.