From Heun Class Equations to Painlevé Equations

Jan Dereziński ; Artur Ishkhanyan ; Adam Latosiński

Symmetry, integrability and geometry: methods and applications, Tome 17 (2021)

Résumé

In the first part of our paper we discuss linear 2nd order differential equations in the complex domain, especially Heun class equations, that is, the Heun equation and its confluent cases. The second part of our paper is devoted to Painlevé I–VI equations. Our philosophy is to treat these families of equations in a unified way. This philosophy works especially well for Heun class equations. We discuss its classification into 5 supertypes, subdivided into 10 types (not counting trivial cases). We also introduce in a unified way deformed Heun class equations, which contain an additional nonlogarithmic singularity. We show that there is a direct relationship between deformed Heun class equations and all Painlevé equations. In particular, Painlevé equations can be also divided into 5 supertypes, and subdivided into 10 types. This relationship is not so easy to describe in a completely unified way, because the choice of the “time variable” may depend on the type. We describe unified treatments for several possible “time variables”.

Détail

Keywords: linear ordinary differential equation
Mots-clés : Heun class equations, isomonodromy deformations, Painlevé equations.

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