Parametric Centers for Trigonometric Abel Equations
Résumé
his article is devoted to one-dimensional perturbative theory on R × S1. There is a recursive formula for the successive obstructions to parametric center at any order of the perturbation parameter. The first obstruction is studied by means of complex analysis techniques. This extends to the trigonometric case what was done previously for the polynomial case (Israel J. Math. 142, 273–283, 2004).