The Monotonicity of Period Function for Codimension Four Quadratic System Q4

In this paper, we study the codimension four quadratic system Q4 : =−iz+4z2+2 z 2+(b+ic)2, where b and c are real constants, i2=−1, z=x+iy, b+ic =2. It is proved that the period function of periodic trajectories for Q4 is monotone. The content of this paper can be viewed as a contribution to the proof of Chiconeʹs conjecture (cf. MR: 94h:58072).