Transverse fundamental group and projected embeddings

TL;DR

This paper introduces the transverse fundamental group for generic maps, explores its properties, and applies it to determine conditions for lifting maps to embeddings, revealing new algebraic-topological obstructions.

Contribution

It defines the transverse fundamental group for generic maps and demonstrates its use in analyzing embedding liftability, a novel approach in topology.

Findings

  can be non-trivial for simple degree 1 maps.

Lifting maps to embeddings requires the monodromy to factor through string link concordance classes.

For degrees less than 7,  must be torsion-free for such lifts to exist.

Abstract

For a generic degree d smooth map f: N^n -> M^n we introduce its "transverse fundamental group" \pi(f), which reduces to \pi_1(M) in the case where f is a covering, and in general admits a monodromy homomorphism \pi(f) -> S_{|d|}; nevertheless, we show that \pi(f) can be non-trivial already for rather simple degree 1 maps S^n -> S^n. We apply \pi(f) to the problem of lifting f to an embedding N -> M x R^2: for such a lift to exist, the monodromy \pi(f) -> S_{|d|} must factor through the group of concordance classes of |d|-component string links. At least if |d|<7, this requires \pi(f) to be torsion-free.