PROJECTIONS OF CODIMENSION TWO EMBEDDINGS

We consider smooth knottings of compact n-dimensional manifolds (not neces­ sarily orientable) in R (or S). We generalize to higher dimensions the classical notion of a knotting in general position with respect to projection. It is shown that any knotting is equivalent to one which is in general position with respect to pro­ jection. In higher dimensions, unlike classical knot theory, a generic projection is not necessarily an immersion. Thus we need to consider maps such that the set of non-immersion points is well behaved. The geometry of projections is exam­ ined and we use this information to show that any smooth knotting of an orientable n-manif old in R is smoothly isotopic to one whose projection into R is an im­ mersion. As corollary we obtain an elementary geometric proof that an orientable n-dimensional submanifold of R has trivial normal bundle. 1980 Mathematics Subject Classification: Primary 57R40, 57R42, 57R45, 57R52, 57Q45.