Analytic continuation and fixed points of the Poincare mapping for a polynomial Abel equation

Abstract

We consider an Abel polynomial differential equation. For two given points a and b, the "Poincare mapping" of the equation transforms the values of its solution at a into their values at b. In this article, we study global analytic properties of the Poincare mapping, in particular, its analytic continuation, its singularities and its fixed points. On one side, we give a general description of singularities of the Poincare mapping, and of its analytic continuation. On the other side, we study in detail the structure of the Poincare mapping for a local model near a simple fixed singularity, where an explicit solution can be written. Yet, the global analytic structure (in particular the ramification) of the solutions and of the Poincare mapping in this case is fairly complicated, and, in our view highly instructive. For a given degree of the coefficients we produce examples with an infinite number of complex periodic solutions and analyze their mutual position and branching. Let us remind that Pugh's problem, which is closely related to the classical Hilbert's 16th problem, asks for the existence of a bound to the number of real isolated periodic solutions.