报告题目: The Maximal Number of Limit Cycles of a Class of Quadratic Vector Field With Nilpotent elliptic point
演讲人： Prof. Huaiping Zhu (York University)
时间： 2010年6月10日（星期四）下午3：30--4：30
地点： 华东师大闵行校区数学系102报告厅

Abstract.
In this talk, I will introduce the study of the exact cyclicity (maximal number of limit cycles) in a class of quadratic vector fields with a center and a family of nilpotent graphics. By using global blow-up technique, I will show you that the bifurcation of the graphics with a nilpotent point will gives rise to at most two limit cycles. Iliev proved that the bifurcation of the center in such family can generate at most three limit cycles, thus we can conclude that this family of quadratic vector fields have at most 4 limit cycles.