Four five-parametric and five four-parametric independent confluent Heun potentials for the stationary Klein-Gordon equation

TL;DR

This paper introduces fifteen solvable potentials for the stationary Klein-Gordon equation using confluent Heun functions, highlighting their parametric diversity and the role of hypergeometric sub-potentials.

Contribution

It identifies and classifies fifteen independent confluent Heun potentials for the Klein-Gordon equation, including new multi-parametric cases with hypergeometric sub-potentials.

Findings

Nine independent potentials due to symmetry considerations.

Four five-parametric potentials with hypergeometric sub-potentials.

Five four-parametric potentials with solutions in irreducible confluent Heun functions.

Abstract

We present in total fifteen potentials for which the stationary Klein-Gordon equation is solvable in terms of the confluent Heun functions. Because of the symmetry of the confluent Heun equation with respect to the transposition of its regular singularities, only nine of the potentials are independent. Four of these independent potentials are five-parametric. One of them possesses a four-parametric ordinary hypergeometric sub-potential, another one possesses a four-parametric confluent hypergeometric sub-potential, and one potential possesses four-parametric sub-potentials of both hypergeometric types. The fourth five-parametric potential has a three-parametric confluent hypergeometric sub-potential, which is, however, only conditionally integrable. The remaining five independent Heun potentials are four-parametric and have solutions only in terms of irreducible confluent Heun functions.