Differential Equations for Approximate Solutions of Painlev\'e Equations: Application to the Algebraic Solutions of the Painlev\'e-III $({\rm D}_7)$ Equation

Autor: Buckingham, Robert J., Miller, Peter D.
Rok vydání: 2023
Předmět:
Zdroj: SIGMA 20 (2024), 008, 27 pages
Druh dokumentu: Working Paper
DOI: 10.3842/SIGMA.2024.008
Popis: It is well known that the Painlev\'e equations can formally degenerate to autonomous differential equations with elliptic function solutions in suitable scaling limits. A way to make this degeneration rigorous is to apply Deift-Zhou steepest-descent techniques to a Riemann-Hilbert representation of a family of solutions. This method leads to an explicit approximation formula in terms of theta functions and related algebro-geometric ingredients that is difficult to directly link to the expected limiting differential equation. However, the approximation arises from an outer parametrix that satisfies relatively simple conditions. By applying a method that we learned from Alexander Its, it is possible to use these simple conditions to directly obtain the limiting differential equation, bypassing the details of the algebro-geometric solution of the outer parametrix problem. In this paper, we illustrate the use of this method to relate an approximation of the algebraic solutions of the Painlev\'e-III (D$_7$) equation valid in the part of the complex plane where the poles and zeros of the solutions asymptotically reside to a form of the Weierstrass equation.
Databáze: arXiv