Erdélyi-type integrals for $F_K$ function and their $q$-analogues
Liang-Jia Guo, Min-Jie Luo
TL;DR
The paper addresses Erdélyi-type integrals for Saran's multivariate $F_K$-function by delivering a new direct proof of a key Erdélyi-type integral and deriving a novel integral for Appell's $F_2$. It generalizes the framework to the $L$-variable $F_K$ (relevant in physics) and develops several $q$-analogs, including a Joshi–Vyas type theorem, a discrete $q$-analog, and a $q$-analogue of the main theorem, all supported by Dirichlet-type measures and basic hypergeometric functions. An Appendix catalogs known Erdélyi-type integrals across diverse hypergeometric functions, highlighting the historical and methodological landscape. Collectively, the results expand analytic tools for multivariate hypergeometric integrals and their $q$-deformations, with potential implications in mathematical physics, fractional calculus, and special function theory.
Abstract
In this paper, we revisit the recent result of Luo, Xu, and Raina [Fractal Fract. 6 (3) (2022)] on an Erdélyi-type integral for Saran's three-variable hypergeometric function $F_K$. We provide a new proof of this integral and derive an attractive new integral related to Appell's function $F_2$. A further extension on the $L$-variable $F_K$ function, which appears in physics, is also discussed. Furthermore, we prove various $q$-Erdélyi-type integrals for the $q$-analogue of the $F_K$-function. An interesting discrete analogue is also included. We also provide a valuable compilation of the sources for known Erdélyi-type integrals of many different hypergeometric functions in the Appendix.
