© 2009 London Mathematical Society
The almost alternating diagrams of the trivial knot
Department of Mathematics, Osaka Institute of Technology, Asahi, Osaka 535-8585, Japan, tsukamoto@ge.oit.ac.jp
| Abstract |
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Bankwitz characterized the alternating diagrams of the trivial knot. A non-alternating diagram is called almost alternating if one crossing change makes the diagram alternating. We characterize the almost alternating diagrams of the trivial knot. As a corollary, we determine the unknotting number one alternating knots with the property that the unknotting operation can be done on its alternating diagram.
Received July 3, 2007. Revised September 29, 2008.
2000 Mathematics Subject Classification 57M25