Order One Invariants of Immersions

Abstract

We classify all order one invariants of immersions of a closed orientable surface F into R^3, with values in an arbitrary Abelian group G. We show that for any F and G and any regular homotopy class A of immersions of F into R^3, the group of all order one invariants on A is isomorphic to G^\aleph_0 \oplus B \oplus B where G^\aleph_0 is the group of all functions from a set of cardinality \aleph_0 into G and B={x\in G : 2x=0}. Our work includes foundations for the study of finite order invariants of immersions of a closed orientable surface into R^3, analogous to chord diagrams and the 1-term and 4-term relations of knot theory.