利用一阶Melnikov函数,考虑一类具有不变曲线1-x2=0的平面三次多项式微分系统的极限环个数问题。通过对该系统的中心进行分段光滑三次多项式扰动,证明了从该系统中心的周期环域可以分支出5个极限环。
This paper studies the number of the limit cycles bifurcating from the periodic annulus of the center for a class of cubic polynomial differential systems and having invariant curves 1-x^2=0, using the first order Melnikov functions. By piecewise smooth cubic polynomial perturbations, we prove that five limit cycles can bifurcate from the periodic orbits.