Proceedings of the American Mathematical Society

Author(s): Tomomi Kawamura
Journal: Proc. Amer. Math. Soc. 130 (2002), 243-252.
MSC (2000): Primary 57M25
Posted: May 7, 2001
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In this paper, we estimate the unknotting number and the four-dimensional clasp number of a link, considering the greatest euler characteristic for an oriented two-manifold in the four-ball bounded by the link. Combining with a result due to Rudolph, we prove that an inequality stronger than the Bennequin unknotting inequality actually holds for any link diagram. As an application we show the equality conjectured by Boileau and Weber for a closed positive braid diagram.

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Retrieve articles in Proceedings of the American Mathematical Society with MSC (2000): 57M25

Tomomi Kawamura
Affiliation: Graduate School of Mathematical Sciences, University of Tokyo, 3-8-1 Komaba Meguro-ku, Tokyo 153-8914, Japan
Email: kawamura@ms.u-tokyo.ac.jp

DOI: 10.1090/S0002-9939-01-06000-2
PII: S 0002-9939(01)06000-2
Keywords: Unknotting number, 4-dimensional clasp number, Bennequin unknotting inequality
Received by editor(s): October 4, 1999
Received by editor(s) in revised form: May 12, 2000
Posted: May 7, 2001
Additional Notes: The author was partially supported by JSPS Research Fellowships for Young Scientists
Communicated by: Ronald A. Fintushel
Copyright of article: Copyright 2001, American Mathematical Society

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