In principle, Floer theory can be extended to define homotopy invariants of families of equivalent objects (eg Hamiltonian isotopic symplectomorphisms, 3-manifolds, Legendrian knots, etc.) parametrized by a smooth manifold B . The invariant of a family consists of a filtered chain homotopy type, which gives rise to a spectral sequence whose E 2 term is the homology of B with local coefficients in the Floer homology of the fibers. This filtered chain homotopy type also gives rise to a "family Floer homology" to which the spectral sequence converges. For any particular version of Floer theory, some analysis needs to be carried out in order to turn this principle into a theorem. This paper constructs the invariant in detail for the model case of finite dimensional Morse homology, and shows that it recovers the Leray-Serre spectral sequence of a smooth fiber bundle. We also generalize from Morse homology to Novikov homology, which involves some additional subtleties.
57R58Floer theory is a certain kind of generalization of Morse theory, of which there are now a number of different flavors. These give invariants of symplectomorphisms, 3-manifolds, Legendrian knots, and many other types of objects. This paper describes a fundamental structure which apparently exists in most or all versions of Floer theory. The structure in question is a homotopy invariant of families of equivalent objects parametrized by a smooth manifold B . Its different manifestations thus give invariants of families of Hamiltonian isotopic symplectomorphisms, families of 3-manifolds, etc. The invariant of a family consists of a filtered chain homotopy type, which gives rise to a spectral sequence whose E 2 term is the homology of B with local coefficients in the Floer homology of the fibers. This filtered chain homotopy type also gives rise to a "family Floer homology" to which the spectral sequence converges.The general properties of this family invariant are stated in the "Main Principle" below. This principle cannot be formulated as a general theorem, because there is no precise definition of "Floer theory" that encompasses all of its diverse variants. For any particular version of Floer theory, in order to turn the principle into a theorem, one needs to slightly extend the construction of the Floer theory in question and check that the requisite analysis goes through. The rest of this paper constructs the invariant in detail for the model version of Floer theory, namely finite-dimensional Morse homology, in language designed to carry over to other versions of Floer theory. In this model situation, a family consists a smooth fiber bundle whose fibers are closed manifolds, with a family of (generically Morse) functions of the fibers. Here it turns out that the family invariant recovers the Leray-Serre spectral sequence of the fiber bundle.The outline of this paper is as follows. The Main Principle is enunciated in Section 1. Section 2 reviews some aspects of the Morse complex that will be needed here. The spectral sequence and family Floer homol...