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Let N be a closed manifold satisfying a mild homotopy assumption. Then for
any exact Lagrangian L ⊂ T*N the map π2(L) → π2(N) has finite index.
The homotopy assumption is either that N is simply connected, or more
generally that πm(N) is finitely generated for each m ≥ 2. The manifolds
need not be orientable, and we make no assumption on the Maslov class of
L.
We construct the Novikov homology theory for symplectic cohomology, denoted
SH*(M;Lα), and we show that Viterbo functoriality holds. We prove that the
symplectic cohomology SH*(T*N;Lα) is isomorphic to the Novikov homology of the
free loopspace. Given the homotopy assumption on N, we show that this Novikov
homology vanishes when α in H1(L0N) is the transgression of a nonzero class in
H2(Ñ). Combining these results yields the above obstructions to the existence of
L.
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