A constructive proof of the Cauchy–Kovalevskaya theorem for ordinary differential equations

S. Kepley, T. Zhang

Research output: Contribution to JournalArticleAcademicpeer-review


© 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG part of Springer Nature.We give a constructive proof of the classical Cauchy–Kovalevskaya theorem for ordinary differential equations which provides a sufficient condition for an initial value problem to have a unique, analytic solution. Our proof is inspired by a modern numerical technique for rigorously solving nonlinear problems known as the radii polynomial approach. The main idea is to recast the existence and uniqueness of analytic solutions as a fixed point problem on an appropriately chosen Banach space, and then prove a fixed point exists via a constructive version of the Banach fixed point theorem. A key aspect of this method is the use of an approximate solution which plays a crucial role in the theoretical proof. Our proof is constructive in the sense that we provide an explicit recipe for constructing the fixed point problem, an approximate solution, and the bounds necessary to prove the existence of the fixed point.
Original languageEnglish
Article number7
JournalJournal of Fixed Point Theory and Applications
Issue number1
Publication statusPublished - 1 Mar 2021
Externally publishedYes


The authors wish to thank Konstantin Mischaikow for helpful discussions. S.K. was partially supported by NSF grant 1839294, by NIH-1R01GM126555-01 as part of the Joint DMS/NIGMS Initiative to Support Research at the Interface of the Biological and Mathematical Science and DARPA contract HR001117S0003-SD2-FP-011. T.Z. was partially supported by the Training Program for Top Students in Mathematics from Zhejiang University.

FundersFunder number
National Science FoundationNIH-1R01GM126555-01
Directorate for Mathematical and Physical Sciences1839294
Defense Advanced Research Projects AgencyHR001117S0003-SD2-FP-011
Zhejiang University


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