Unsolvable problems about higher-dimensional knots and related groups
arXiv:0908.4009
Abstract
We consider classes of fundamental groups of complements of various kinds of codimension 2 embeddings and show that, in general, the problem of deciding whether or not a group in one class belongs to a smaller class is algorithmically unsolvable.
20 pages, AMSLaTeX, accepted for publication in L'Enseignement Mathematique