# Efficient Algorithms for Computing Rational First Integrals and Darboux Polynomials of Planar Polynomial Vector Fields

Abstract : We present fast algorithms for computing rational first integrals with bounded degree of a planar polynomial vector field. Our approach builds upon a method proposed by Ferragut and Giacomini, whose main ingredients are the calculation of a power series solution of a first order differential equation and the reconstruction of a bivariate polynomial annihilating this power series. We provide explicit bounds on the number of terms needed in the power series. This enables us to transform their method into a certified algorithm computing rational first integrals via systems of linear equations. We then significantly improve upon this first algorithm by building a probabilistic algorithm with arithmetic complexity $\~O(N^{2 \omega})$ and a deterministic algorithm solving the problem in at most $\~O(d^2N^{2 \omega+1})$ arithmetic operations, where~$N$ denotes the given bound for the degree of the rational first integral, and where $d \leq N$ is the degree of the vector field, and $\omega$ the exponent of linear algebra. We also provide a fast heuristic variant which computes a rational first integral, or fails, in $\~O(N^{\omega+2})$ arithmetic operations. By comparison, the best previous algorithm uses at least $d^{\omega+1}\, N^{4\omega +4}$ arithmetic operations. We then show how to apply a similar method to the computation of Darboux polynomials. The algorithms are implemented in a Maple package RationalFirstIntegrals which is available to interested readers with examples showing its efficiency.
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Journal articles
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https://hal.archives-ouvertes.fr/hal-00871663
Contributor : Alin Bostan <>
Submitted on : Tuesday, December 23, 2014 - 9:44:18 PM
Last modification on : Thursday, March 5, 2020 - 5:56:42 PM
Long-term archiving on: : Tuesday, March 24, 2015 - 10:06:20 AM

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### Identifiers

• HAL Id : hal-00871663, version 2
• ARXIV : 1310.2778

### Citation

Alin Bostan, Guillaume Chèze, Thomas Cluzeau, Jacques-Arthur Weil. Efficient Algorithms for Computing Rational First Integrals and Darboux Polynomials of Planar Polynomial Vector Fields. Mathematics of Computation, American Mathematical Society, 2016, 85 (299), pp.1393--1425. ⟨hal-00871663v2⟩

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