On the $L^2-$Poincar\'e duality for incomplete riemannian manifolds: a general construction with applications

Abstract

Let $(M,g)$ be an open, oriented and incomplete riemannian manifold of dimension $m$. Under some general conditions we show that it is possible to build a Hilbert complex $(L^2\Omega^i(M,g),d_{\mathfrak{M},i})$ such that its cohomology groups, labeled with $H^i_{2,\mathfrak{M}}(M,g)$, satisfy the following properties: \begin{itemize} \item $H^i_{2,\mathfrak{M}}(M,g)=ker(d_{max,i})/\im(d_{min,i})$ \item $H^i_{2,\mathfrak{M}}(M,g)\cong H^{m-i}_{2,\mathfrak{M}}(M,g)$ (Poincar\'e duality holds) \end{itemize} Finally in the rest of the paper we study some properties of this complex with particular attention to the sufficient conditions which make it a Fredholm complex.