Finite-dimensional irreducible modules of the universal DAHA of type $(C_1^\vee,C_1)$

Abstract: Assume that $\mathbb F$ is an algebraically closed field and let $q$ denote a nonzero scalar in $\mathbb F$ that is not a root of unity. The universal DAHA (double affine Hecke algebra) $\mathfrak H_q$ of type $(C_1^\vee,C_1)$ is a unital associative $\mathbb F$-algebra defined by generators and relations. The generators are ${t_i^{\pm 1}}_{i=0}^3$ and the relations assert that \begin{gather*} t_it_i^{-1}=t_i^{-1} t_i=1 \quad \hbox{for all $i=0,1,2,3$}; \ \hbox{$t_i+t_i^{-1}$ is central} \quad \hbox{for all $i=0,1,2,3$}; \ t_0t_1t_2t_3=q^{-1}. \end{gather*} In this paper we describe the finite-dimensional irreducible $\mathfrak H_q$-modules from many viewpoints and classify the finite-dimensional irreducible $\mathfrak H_q$-modules up to isomorphism. The proofs are carried out in the language of linear algebra.