Twisted Morse complexes

Abstract: In this paper we study Morse homology and cohomology with local coefficients, i.e. "twisted" Morse homology and cohomology, on closed finite dimensional smooth manifolds. We prove a Morse theoretic version of Eilenberg's Theorem, and we prove isomorphisms between twisted Morse homology, Steenrod's CW-homology with local coefficients for regular CW-complexes, and singular homology with local coefficients. By proving Morse theoretic versions of the Poincare Lemma and of the de Rham Theorem, we show that twisted Morse cohomology with coefficients in a local system determined by a closed 1-form is isomorphic to the Lichnerowicz cohomology obtained by deforming the de Rham differential by the 1-form. We demonstrate the effectiveness of twisted Morse complexes by using them to compute Lichnerowicz cohomology, to compute obstructions to spaces being associative H-spaces, and to compute Novikov numbers.