Bimodules in bordered heegaard floer homology

Bordered Heegaard Floer homology is a three-manifold invariant which associates to a surface F an algebra A.F/ and to a three-manifold Y with boundary identified with F a module over A.F/. In this paper, we establish naturality properties of this invariant. Changing the diffeomorphism between F and the boundary of Y tensors the bordered invariant with a suitable bimodule over A.F/. These bimodules give an action of a suitably based mapping class group on the category of modules over A.F/. The Hochschild homology of such a bimodule is identified with the knot Floer homology of the associated open book decomposition. In the course of establishing these results, we also calculate the homology of A.F/. We also prove a duality theorem relating the two versions of the 3–manifold invariant. Finally, in the case of a genus-one surface, we calculate the mapping class group action explicitly. This completes the description of bordered Heegaard Floer homology for knot complements in terms of the knot Floer homology.