|Affiliation||Tokyo Institute of Technology|
|Time||Jan 11 16:00~16:20|
|Title||Finite negative unknotting number and Heegaard Floer homology|
If a knot can be transformed into the unknot by transforming finitely many positive crossings into negative crossings, we say this knot has finite negative unknotting number. Note that the sign of a crossing does not depend on the orientation of the knot. In particular, positive knots have finite negative unknotting number. In this talk, we give an obstruction for a knot to having finite negative unknotting number. This obstruction is derived from Heegaard Floer homology. We show some applications.