On generalized winding numbers

Abstract

Let $M^m$ be an oriented manifold, let $N^{m-1}$ be an oriented closed manifold, and let $p$ be a point in $M^m$. For a smooth map $f:N^{m-1} \to M^m, p \not\in Im f,$ we introduce an invariant $awin_p(f)$ that can be regarded as a generalization of the classical winding number of a planar curve around a point. We show that $awin_p$ estimates from below the number of times a wave front on $M$ passed through a given point $p\in M$ between two moments of time. Invariant $awin_p$ allows us to formulate the analogue of the complex analysis Cauchy integral formula for meromorphic functions on complex surfaces of genus bigger than one.