Infinite-dimensional representations of $U_q(\mathfrak{sl}_2)$ and the shadow world: quantum $6j$-symbols for Verma modules
Dmitry Solovyev
TL;DR
This work extends the shadow world framework from finite-dimensional $U_q(\mathfrak{sl}_2)$ representations to Verma modules by constructing explicit $q3j$-symbols and $q6j$-symbols. It develops a graphical calculus for these infinite-dimensional objects, proves key orthogonality, Racah, BE, and Yang–Baxter identities within the shadow world, and introduces the functional ${\mathsf{SW}}_\infty$ together with the notion of polarized modules as a potential target category for a Reshetikhin–Turaev-type theory. By connecting to the Gukov–Manolescu program via $F_K(x,q)$ and studying the trefoil as a diagnostic example, the paper lays out a roadmap for a non-perturbative, functorial framework that reconciles edge- and face-state perspectives in the infinite-dimensional setting. The results offer a pathway toward a categorified, topological invariant theory that encompasses Verma-module colorings and informs the structure of the Grothendieck ring for an RT-like functor in this broader representation-theoretic context.
Abstract
This paper initiates the study of invariants of links associated to infinite-dimensional representations of $U_q(\mathfrak{sl}_2)$ using graphical representation for quantum $6j$-symbols, the shadow world. We obtain formulae for $q3j$-symbols and $q6j$-symbols for Verma modules and study their properties. This hints at the structure of the possible target category for Reshetikhin-Turaev functor for such an invariant.
