Geometry and Topology Seminar —— Ribbon knots and Symmetric unions
报告人：Michel Boileau （Aix-Marseille University）
时间：2026-05-13 15:10-17:00
地点：智华楼四元厅（225）
【摘要】
The symmetric union is a construction introduced by Kinoshita-Terasaka in 1957 and extended by Lamm in 2000, which gives an efficient method to produce ribbon knots. Up to 12 crossings, all but 15 prime ribbon knots are known to admit a symmetric union presentation. Whether every ribbon knot can be presented as a symmetric union is a basic question in the study of ribbon knots, as it would provide a diagrammatic characterization of being ribbon. The main purpose of this talk is to give a negative answer to this question by exhibiting a ribbon knot which does not admit a symmetric union presentation. This is a joint work with Teruaki Kitano and Yuta Nozaki.
