Abstract. The first two authors have recently defined RabinowitzFloer homology groups RF H * (M, W ) associated to an exact embedding of a contact manifold (M, ξ) into a symplectic manifold (W, ω). These depend only on the bounded component V of W \ M . We construct a long exact sequence in which symplectic cohomology of V maps to symplectic homology of V , which in turn maps to Rabinowitz-Floer homology RF H * (M, W ), which then maps to symplectic cohomology of V . We compute RF H * (ST * L, T * L), where ST * L is the unit cosphere bundle of a closed manifold L. As an application, we prove that the image of an exact contact embedding of ST * L (endowed with the standard contact structure) cannot be displaced away from itself by a Hamiltonian isotopy, provided dim L ≥ 4 and the embedding induces an injection on π1. In particular, ST * L does not admit an exact contact embedding into a subcritical Stein manifold if L is simply connected. We also prove that Weinstein's conjecture holds in symplectic manifolds which admit exact displaceable codimension 0 embeddings.
IntroductionLet (W, λ) be a complete convex exact symplectic manifold, with symplectic form ω = dλ (see Section 3 for the precise definition). An embedding ι : M ֒→ W of a contact manifold (M, ξ) is called exact contact embedding if there exists a 1-form α on M such that such that ker α = ξ and α − λ| M is exact. We identify M with its image ι(M ). We assume that W \ M consists of two connected components and denote the bounded component of W \ M by V . One can classically [25] associate to such an exact contact embedding the symplectic (co)homology groups SH * (V ) and SH * (V ). We The first two authors have recently defined for such an exact contact embedding Floer homology groups RF H * (M, W ) for the Rabinowitz action functional [9]. We refer to Section 3 for a recap of the definition and of some useful properties. We will show in particular that these groups do not depend on W , but only on V (the same holds for SH * (V ) and SH * (V )). We shall use in this paper the notation RF H * (V ) and call them Rabinowitz Floer homology groups. Remark 1.1. All (co)homology groups are taken with field coefficients. Without any further hypotheses on the first Chern class c 1 (V ) of the tangent bundle, the symplectic (co)homology and Rabinowitz Floer homology groups are Z 2 -graded. If c 1 (V ) = 0 they are Z-graded, and if c 1 (V ) vanishes on π 2 (V ) the part constructed from contractible loops is Z-graded. This Zgrading on Rabinowitz Floer homology differs from the one in [9] (which takes values in 1 2 + Z) by a shift of 1/2 (see Remark 3.2).Our purpose is to relate these two constructions. The relevant object is a new version of symplectic homology, denotedŠH * (V ), associated to " -shaped" Hamiltonians like the one in Figure 1 on page 20 below. This version of symplectic homology is related to the usual ones via the long exact sequence in the next theorem. Theorem 1.2. There is a long exact sequence (1). . .The long exact sequence (1) can be seen ...