Extending immersed circles in the sphere to immersed disks in the ball
The author considers a general position immersion of a circle into the 2- sphere with an even number of double points. Then between all immersions of the 2-disk in the 3-ball having the given curve as boundary, there is one with a minimum number of triple points. This minimum is obtained algorithmically in terms of a number that is associated to the Gauss word defined by the double point set of the immersed circle.
general position immersion of a circle into the 2-sphere with an even number of double points
scientific article; zbMATH DE number 86172