**Thời gian:** 9h00 thứ 6 ngày 09/10/2015,

**Báo cáo viên;** TS. Đoàn Thái Sơn (Viện Toán học).

**Tên báo cáo:** Gevrey normal form for unfoldings of nilpotent contact points of planar slow fast systems.

**Tóm tắt:** We present normal forms for unfoldings of regular nilpotent contact points of slow-fast systems in the plane. The normal forms are useful in the treatment of non-generic jump points and non-generic turning points. For non-generic jump points, we prove a normal form of Li enard type, while for non-generic turning points, the normal form is of Li enard type up to exponentially small error. The techniques being used are based on Gevrey estimates on formal power series, summation up to exponentially small error and a Gevrey version of the preparation theorem for right equivalences. This extension of earlier results is based on a Gevrev version of Levinson's preparation theorem, which we prove.