On geometric bases for A-polynomials II: $\mathfrak{su}_3$ and Kuberberg bracket

Abstract

We continue the study of quantum A-polynomials -- equations for knot polynomials with respect to their coloring (representation-dependence) -- as the relations between different links, obtained by hanging additional ``simple'' components on the original knot. Depending on the choice of this ``decoration'', the knot polynomial is either multiplied by a number or decomposes into a sum over ``surrounding'' representations by a cabling procedure. What happens is that these two of decorations, when complicated enough, become dependent -- and this provides an equation. Remarkably it can be made independent of the representation. However, the equivalence of links is not a topological property -- it follows from the properties of $R$-matrices, and strongly depends on the choice the gauge group and particular links. The relatively well studied part of the story concerns $\mathfrak{su}_2$, where $R$-matrices can be chosen in an especially convenient Kauffman form, what makes the derivation of equations rather geometrical. To make these geometric methods somewhat simpler we suggest to use an arcade formalism/representation of the braid group to simplify decorating links universally. Here we attempt to extend this technique to the next case, $\mathfrak{su}_3$, where the Kauffman rule is substituted by a more involved Kuberberg rule, still remains more geometric than generic analysis of MOY-diagrams, needed for higher ranks. Already in this case we encounter a classification problem for possible ``decorations'' and emergence of two-lined Young diagrams in enumeration of representations.