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Immersions of non-orientable surfaces
Authors:Tahl Nowik
Institution:Department of Mathematics, Bar-Ilan University, Ramat-Gan 52900, Israel
Abstract:Let F be a closed non-orientable surface. We classify all finite order invariants of immersions of F into R3, with values in any Abelian group. We show they are all functions of a universal order 1 invariant which we construct as TPQ, where T is a Z valued invariant reflecting the number of triple points of the immersion, and P,Q are Z/2 valued invariants characterized by the property that for any regularly homotopic immersions View the MathML source, P(i)−P(j)∈Z/2 (respectively, Q(i)−Q(j)∈Z/2) is the number mod 2 of tangency points (respectively, quadruple points) occurring in any generic regular homotopy between i and j.For immersion View the MathML source and diffeomorphism View the MathML source such that i and ih are regularly homotopic we show:
P(ih)−P(i)=Q(ih)−Q(i)=(rank(h−Id)+ε(deth∗∗))mod2
Keywords:Immersions of surfaces  Finite order invariants
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