Geometry of free products
The rank of the free factor of a subgroup \(\Phi\) of a free product \(\Gamma =\prod^{*}_{i\in I}\Gamma_ i\) given by Kurosh's theorem is a well-defined invariant of \(\Phi\) as a subgroup of \(\Gamma\) and it has some analogies with the genus and the number of cusps of a subgroup of a fuchsian group. We explain these analogies by means of the diagrams and their thickenings introduced in an earlier paper and give extensions of a number of results by Greenberg, Millington, Newman, Rosenberger, Zieschang....
scientific article; zbMATH DE number 3935297
scientific article