Representations and Classification of the compact quantum groups $U_q(2)$ for complex deformation parameters

TL;DR

This paper provides a comprehensive classification and explicit representation theory of the quantum group U_q(2) for non-zero complex deformation parameters, including Fourier analysis and tensor product decompositions.

Contribution

It offers a complete classification of irreducible representations of U_q(2) and explicit descriptions of their matrix coefficients using little q-Jacobi polynomials.

Findings

Complete list of inequivalent irreducible representations.

Explicit Peter-Weyl decomposition of U_q(2).

Classification of the quantum groups U_q(2).

Abstract

In this article, we obtain a complete list of inequivalent irreducible representations of the compact quantum group $U_q(2)$ for non-zero complex deformation parameters $q$, which are not roots of unity. The matrix coefficients of these representations are described in terms of the little $q$-Jacobi polynomials. The Haar state is shown to be faithful and an orthonormal basis of $L^2(U_q(2))$ is obtained. Thus, we have an explicit description of the Peter-Weyl decomposition of $U_q(2)$. As an application, we discuss the Fourier transform and establish the Plancherel formula. We also describe the decomposition of the tensor product of two irreducible representations into irreducible components. Finally, we classify the compact quantum groups $U_q(2)$.