Gauss decomposition and $q$-difference equations for Jackson integrals of symmetric Selberg type

Abstract: We provide explicit expressions for two types of first order $q$-difference systems for the Jackson integral of symmetric Selberg type. One is the $q$-difference system known to be the $q$-KZ equation and the other is the $q$-difference system for parameters different from the $q$-KZ equation. We use a basis of the systems introduced by Matsuo in his study of the $q$-KZ equation. As a result, the similarity of these two systems is discussed by concrete calculations. Intermediate calculations are made use of the Riemann-Hilbelt method for $q$-difference equation from connection matrix established by Aomoto.