C^0-generic properties of boundary operators in Novikov Complex
Résumé
One of the basic objects in the Morse theory of circle-valued maps is Novikov complex - an analog of the Morse complex of Morse functions. Novikov complex is defined over the ring of Laurent power series with finite negative part. The main aim of this paper is to present a detailed and self-contained exposition of the author's theorem saying that C^0-generically the Novikov complex is defined over the ring of rational functions. The paper contains also a systematic treatment of the topics of the classical Morse theory related to Morse complexes (Chapter 2). We work with a new class of gradient-type vector fields, which includes riemannian gradients. In Ch.3 we suggest a purely Morse-theoretic (not using triangulations) construction of small handle decomposition of manifolds. In the Ch.4 we deal with the gradients of Morse functions on cobordisms. Due to the presence of critical points the descent along the trajectories of such gradient does no define in general a continuous map from the upper component of the boundary to the lower one. We show that for C^0-generic gradients there is an algebraic model of "gradient descent map". This is one of the main tools in the proof of the main theorem (Chapter 5). We give also the generalizations of the result for the versions of Novikov complex defined over completions of group rings (non commutative in general).