Uniform Approach to Double Shuffle and Duality Relations of Various q-Analogs of Multiple Zeta Values via Rota–Baxter Algebras

Abstract

The multiple zeta values (MZVs) have been studied extensively in recent years. Currently there exist a few different types of $q$-analogs of the MZVs ($q$-MZVs) defined and studied by mathematicians and physicists. In this paper, we give a uniform treatment of these $q$-MZVs by considering their double shuffle relations (DBSFs) and duality relations. The main idea is a modification and generalization of the one used by Castillo Medina et al. who have considered the DBSFs of a special type of $q$-MZVs. We generalize their method to a few other types of $q$-MZVs including the one defined by the author in 2003. With different approach, Takeyama has already studied this type by "regularization" and observed that there exist $\mathbb Q$-linear relations which are not consequences of the DBSFs. He also discovered a new family of relations which we call the duality relations in this paper. This deficiency of DBSFs occurs among other types, too, so we generalize the duality relations to all of these values and find that there are still some missing relations. This leads to the most general type of $q$-MZVs together with a new kind of relations called $\bf P$-$\bf Q$ relations which are used to lower the deficiencies further. As an application, we will confirm a conjecture of Okounkov on the dimensions of certain $q$-MZV spaces, either theoretically or numerically, for the weight up to 12. Some relevant numerical data are provided at the end.