本文研究了一类原点为幂零奇点的五次微分系统,通过计算系统的前7个Lyapunov常数,得到了系统的原点为中心的充要条件,并证明了系统在原点至多能够分支出5个极限环.同时研究了系统其余四个奇点(±1,0),(0,±1)的中心焦点问题,分别得到了系统存在5个中心、3个中心的条件.
In this paper,a class of quinic polynomial differential system with nilpotent critical point are investigated.The first 7 quasi Lyapunov constants are deduced with the help of computer algebra system mathematica.As a result,the sufficient and necessary conditions of the center in the system are derived.There exist 5 small amplitude limit cycles created from the three order nilpotent critical point is also proved.Others critical points(±1,0),(0,±1) are researched at the same condition,the sufficient and necessary conditions of existing five or three centers in the system are obtained respectively.