Transverse fundamental group and projected embeddings
arXiv:1505.00505
Abstract
For a generic degree d smooth map f: N^n -> M^n we introduce its "transverse fundamental group" π(f), which reduces to π_1(M) in the case where f is a covering, and in general admits a monodromy homomorphism π(f) -> S_{|d|}; nevertheless, we show that π(f) can be non-trivial already for rather simple degree 1 maps S^n -> S^n. We apply π(f) to the problem of lifting f to an embedding N -> M x R^2: for such a lift to exist, the monodromy π(f) -> S_{|d|} must factor through the group of concordance classes of |d|-component string links. At least if |d|<7, this requires π(f) to be torsion-free.
14 pages, 1 figure; minor changes (figure redrawn, etc.)