7 citations · 8 across the 7 of their papers we have counts for
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The first return map for planar vector fields with nilpotent linear part with a center or a focus
Rodica D. Costin
The return map for planar vector fields with nilpotent linear part (having a center or a focus and under an assumption generically satisfied) is found as a convergent power series…
The return map for a planar vector field with nilpotent linear part: a direct and explicit derivation
Rodica D. Costin
Using a direct approach the return map near a focus of a planar vector field with nilpotent linear part is found as a convergent power series which is a perturbation of the identit…
Orthogonality of Jacobi and Laguerre polynomials for general parameters via the Hadamard finite part
Rodica D. Costin
Orthogonality of the Jacobi and of Laguerre polynomials, P_n^(a,b) and L_n^(a), is established for a,b complex (a,b not negative integers and a+b different from -2,-3,...) using th…
Analytic linearization of nonlinear perturbations of Fuchsian systems
Rodica D. Costin
Nonlinear perturbation of Fuchsian systems are studied in regions including two singularities. Such systems are not necessarily analytically equivalent to their linear part (they a…
Rigorous WKB for finite order linear recurrence relations with smooth coefficients
O. Costin, R. D. Costin
We study the behavior of recurrence relations of the type $k\in \zdd$ ( fixed). The are functions in each variable…
Rigorous bounds of Stokes constants for some nonlinear ODEs at rank one irregular singularities
O. Costin, R. D. Costin, M. Kohut
A rigorous way to obtain sharp bounds for Stokes constants is introduced and illustrated on a concrete problem arising in applications.