Double point self-intersection surfaces of immersions

Abstract

A self-transverse immersion of a smooth manifold M^{k+2} in R^{2k+2} has a double point self-intersection set which is the image of an immersion of a smooth surface, the double point self-intersection surface. We prove that this surface may have odd Euler characteristic if and only if k is congruent to 1 modulo 4 or k+1 is a power of 2. This corrects a previously published result by Andras Szucs. The method of proof is to evaluate the Stiefel-Whitney numbers of the double point self-intersection surface. By earier work of the authors these numbers can be read off from the Hurewicz image h(α) in H_{2k+2}Ω^{\infty }Σ^{\infty }MO(k) of the element αin π_{2k+2}Ω^{\infty }Σ^{\infty }MO(k) corresponding to the immersion under the Pontrjagin-Thom construction.

22 pages. Published copy, also available at http://www.maths.warwick.ac.uk/gt/GTVol4/paper4.abs.html