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We use the criteria of Lalonde and McDuff to show that a path that is
generated by a generic autonomous Hamiltonian is length minimizing with
respect to the Hofer norm among all homotopic paths provided that it
induces no non-constant closed trajectories in M. This generalizes a
result of Hofer for symplectomorphisms of Euclidean space. The proof
for general M uses Liu–Tian's construction of S1–invariant
virtual moduli cycles. As a corollary, we find that any semifree action
of S1 on M gives rise to a nontrivial element in the fundamental
group of the symplectomorphism group of M. We also establish a version
of the area-capacity inequality for quasicylinders.
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