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We use Floer homology to study the Hofer–Zehnder capacity of neighborhoods near a
closed symplectic submanifold M of a geometrically bounded and symplectically
aspherical ambient manifold. We prove that, when the unit normal bundle of M is
homologically trivial in degree dim(M) (for example, if codim(M) > dim(M)), a
refined version of the Hofer–Zehnder capacity is finite for all open sets close enough
to M. We compute this capacity for certain tubular neighborhoods of M by using a
squeezing argument in which the algebraic framework of Floer theory is used to
detect nontrivial periodic orbits. As an application, we partially recover some
existence results of Arnold for Hamiltonian flows which describe a charged particle
moving in a nondegenerate magnetic field on a torus. Following an earlier paper, we
also relate our refined capacity to the study of Hamiltonian paths with minimal Hofer
length.
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