  Consider the cotangent bundle of a closed Riemannian manifold and an almost
complex structure close to the one induced by the Riemannian metric. For
Hamiltonians which grow for instance quadratically in the fibers outside of a
compact set, one can define Floer homology and show that it is naturally
isomorphic to singular homology of the free loop space. We review the three
isomorphisms constructed by Viterbo (1996), Salamon-Weber (2003) and
Abbondandolo-Schwarz (2004).
  The theory is illustrated by calculating Morse and Floer homology in case of
the euclidean n-torus. Applications include existence of noncontractible
periodic orbits of compactly supported Hamiltonians on open unit disc cotangent
bundles which are sufficiently large over the zero section.
