We prove a Poincar\'e duality theorem with products between Rabinowitz Floer
homology and cohomology, for both closed and open strings. This lifts to a
duality theorem between open-closed TQFTs. Specializing to the case of
cotangent bundles, we define extended loop homology and cohomology and explain
from a unified perspective pairs of dual results which have been observed over
the years in the context of the search for closed geodesics. These concern
critical levels, relations to the based loop space, manifolds all of whose
geodesics are closed, Bott index iteration, level-potency, and homotopy
invariance. We extend the loop cohomology product to include constant loops. We
prove a relation conjectured by Sullivan between the loop product and the
extended loop homology coproduct as a consequence of associativity for the
product on extended loop homology.Comment: 87 pages, 14 figure