Singular Perturbation of Nonlinear Systems with Regular Singularity

We extend Balser-Kostov method of studying summability properties of a singularly perturbed inhomogeneous linear system with regular singularity at origin to nonlinear systems of the form εzf′=Fε,z,f with F a Cν-valued function, holomorphic in a polydisc D-ρ×D-ρ×D-ρν. We show that its unique formal...

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Main Authors: Domingos H. U. Marchetti, William R. P. Conti
Format: Article
Language:English
Published: Wiley 2018-01-01
Series:Discrete Dynamics in Nature and Society
Online Access:http://dx.doi.org/10.1155/2018/5163492
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author Domingos H. U. Marchetti
William R. P. Conti
author_facet Domingos H. U. Marchetti
William R. P. Conti
author_sort Domingos H. U. Marchetti
collection DOAJ
description We extend Balser-Kostov method of studying summability properties of a singularly perturbed inhomogeneous linear system with regular singularity at origin to nonlinear systems of the form εzf′=Fε,z,f with F a Cν-valued function, holomorphic in a polydisc D-ρ×D-ρ×D-ρν. We show that its unique formal solution in power series of ε, whose coefficients are holomorphic functions of z, is 1-summable under a Siegel-type condition on the eigenvalues of Ff(0,0,0). The estimates employed resemble the ones used in KAM theorem. A simple lemma is applied to tame convolutions that appear in the power series expansion of nonlinear equations. Applications to spherical Bessel functions and probability theory are indicated. The proposed summability method has certain advantages as it may be applied as well to (singularly perturbed) nonlinear partial differential equations of evolution type.
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issn 1026-0226
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spelling doaj-art-7821b856aaa54b6783080db07e0002822025-08-20T02:07:08ZengWileyDiscrete Dynamics in Nature and Society1026-02261607-887X2018-01-01201810.1155/2018/51634925163492Singular Perturbation of Nonlinear Systems with Regular SingularityDomingos H. U. Marchetti0William R. P. Conti1Instituto de Física, Universidade de São Paulo, Rua do Matão, 1371, 05508-090 São Paulo, SP, BrazilDepartamento de Ciências do Mar, Universidade Federal de São Paulo, Rua Dr. Carvalho de Mendonça 144, 11070-100 Santos, SP, BrazilWe extend Balser-Kostov method of studying summability properties of a singularly perturbed inhomogeneous linear system with regular singularity at origin to nonlinear systems of the form εzf′=Fε,z,f with F a Cν-valued function, holomorphic in a polydisc D-ρ×D-ρ×D-ρν. We show that its unique formal solution in power series of ε, whose coefficients are holomorphic functions of z, is 1-summable under a Siegel-type condition on the eigenvalues of Ff(0,0,0). The estimates employed resemble the ones used in KAM theorem. A simple lemma is applied to tame convolutions that appear in the power series expansion of nonlinear equations. Applications to spherical Bessel functions and probability theory are indicated. The proposed summability method has certain advantages as it may be applied as well to (singularly perturbed) nonlinear partial differential equations of evolution type.http://dx.doi.org/10.1155/2018/5163492
spellingShingle Domingos H. U. Marchetti
William R. P. Conti
Singular Perturbation of Nonlinear Systems with Regular Singularity
Discrete Dynamics in Nature and Society
title Singular Perturbation of Nonlinear Systems with Regular Singularity
title_full Singular Perturbation of Nonlinear Systems with Regular Singularity
title_fullStr Singular Perturbation of Nonlinear Systems with Regular Singularity
title_full_unstemmed Singular Perturbation of Nonlinear Systems with Regular Singularity
title_short Singular Perturbation of Nonlinear Systems with Regular Singularity
title_sort singular perturbation of nonlinear systems with regular singularity
url http://dx.doi.org/10.1155/2018/5163492
work_keys_str_mv AT domingoshumarchetti singularperturbationofnonlinearsystemswithregularsingularity
AT williamrpconti singularperturbationofnonlinearsystemswithregularsingularity