Universal quantum dimensions: $\gamma$-dependent factors

Abstract

We develop an approach for computing the universal, in Vogel's sense, quantum dimensions. In a previous work a method for calculating the $\gamma$-independent part of these dimensions for universal multiplets with nonzero associated members for classical algebras was proposed. In the present paper, this approach is extended to the $\gamma$-dependent factors. In particular, we derive these contributions for the $E$ universal multiplet, which appears in the universal decomposition of the fourth power of the adjoint representation, thereby obtaining its universal quantum dimension for the first time. The analysis requires knowledge of the quantum dimensions of the classical and $E_8$ members of the multiplet; for the remaining exceptional algebras, the corresponding quantum dimensions are recovered automatically, providing an additional consistency check of the approach. We also partially extend a previously conjectured relation between the $sl$ and $so, sp$ members - formulated in terms of vertical and horizontal sums of Young diagrams - to the exceptional case. Finally, we present an explicit algorithm implementing the proposed method, which enables the derivation of universal formulae for higher-dimensional representations. The universal quantum dimensions provide, in some cases, a unified description of Chern-Simons observables, including knot invariants and partition functions, in a form valid simultaneously for all gauge algebras.