Linear estimate for the number of zeros of Abelian integrals with cubic Hamiltonians

An explicit upper boundZ.3;n/6 5nC15 is derived for the number of the zeros of the integral h!I.h/D R HDhg.x;y/dx f.x;y/dy of degreen polynomialsf;g, on the open interval 6 for which the cubic curvefHDhg contains an oval. The proof exploits the properties of the Picard-Fuchs system satisfied by the four basic integrals RR H<hx i y j dx dy ,i;jD 0; 1; generating the module of complete Abelian integrals I.h/ (over the ring of polynomials in h).