An invariant for open virtual strings
arXiv:math/0409185
Abstract
Extended Alexander groups are used to define an invariant for open virtual strings. Examples of non-commuting open strings and a ribbon-concordance obstruction are given. An example is given of a slice virtual open string that is not ribbon. Definitions are extended to open n-strings.
9 pages, 10 figures. Version 2 includes improvements to section 3. To appear in J. Knot Theory and its Ramifications