, Volume 118, Issue 1, pp 83-108

Center conditions III: Parametric and model center problems

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


We consider an Abel equation (*)y’=p(x)y 2 +q(x)y 3 withp(x), q(x) polynomials inx. A center condition for (*) (closely related to the classical center condition for polynomial vector fields on the plane) is thaty 0=y(0)≡y(1) for any solutiony(x) of (*).

Folowing [7], we consider a parametric version of this condition: an equation (**)y’=p(x)y 2 +εq(x)y 3 p, q as above, ε ∈ ℂ, is said to have a parametric center, if for any ɛ and for any solutiony(ɛ,x) of (**)y(ɛ, 0)≡y(ɛ, 1)..

We give another proof of the fact, shown in [6], that the parametric center condition implies vanishing of all the momentsm k (1), wherem k (x)=∫ 0 x pk (t)q(t)(dt),P(x)=∫ 0 x p(t)dt. We investigate the structure of zeroes ofm k (x) and generalize a “canonical representation” ofm k (x) given in [7]. On this base we prove in some additional cases a composition conjecture, stated in [6, 7] for a parametric center problem.