UNKNOTTING NUMBERS AND MINIMAL KNOT DIAGRAMS

Abstract

We show there is an infinite number of knots whose unknotting numbers can only be realized through a sequence of crossing changes on a nonminimal projection, if ambient isotopies between crossing changes are not allowed. In this process, the question arises one crossing change at a time is made, always on a minimal projection, in order to obtain the unknotting number of a knot.