The Relation Between Diagrams of a Knot and Its Unknotting Number

Abstract

The unknotting number is the classical invariant of a knot. However, its determination is difficult in general. To obtain the unknotting number from definition one has to investigate all possible diagrams of the knot. We tried to show the unknotting number can be obtained from any one diagram of the knot. To do this we tried to prove the unknotting number is not changed under Riedemiester moves, but such a proposition is not correct. Reidemeister II move can change unknotting number. See Nakanishi-Bleiler example. So this article is withdrawn.