A CONCRETE EXAMPLE OF THE EXISTENCE OF FOUR LIMIT CYCLES FOR PLANE QUADRATIC SYSTEMS

Abstract

This paper gives a positive answer to an unknown problem as to whether a plane vector field, given by two polynomials of 2nd degree, can have more than 3 limit cycles. This problem was put forward at the symposium on the mathematical consequences of the Hilbert problems, sponsored by the American Mahematical Society in May, 1974.