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Turrittin’s normal forms for linear systems of meromorphic ODEs over the real field. (English) Zbl 1527.34067

Summary: We establish a version of Turrittin’s result on normal forms of linear systems of meromorphic ODEs when the base field \(K\) is real and closed. Both the proposed normal forms and the transformations used have coefficients in \(K\). Our motivation comes from applications to the study of trajectories of real analytic vector fields (already treated in the literature in dimension three). For the sake of clarity and completeness, we first review Turrittin’s theorem in the case of an algebraically closed base field.

MSC:

34C20 Transformation and reduction of ordinary differential equations and systems, normal forms
34C08 Ordinary differential equations and connections with real algebraic geometry (fewnomials, desingularization, zeros of abelian integrals, etc.)
34M03 Linear ordinary differential equations and systems in the complex domain
34M25 Formal solutions and transform techniques for ordinary differential equations in the complex domain

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