Melnikov energy-balance method (source code)

= Melnikov energy-balance method
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For a weak perturbation of a planar <Hamiltonian system>, integrate the first-order <orbital derivative> of the Hamiltonian along an unperturbed homoclinic orbit. This measures the first-order separation of stable and unstable manifolds on a transverse section. A simple zero as a parameter varies permits a nearby homoclinic connection by the implicit function theorem. The resulting leading balance is not a claim that the unperturbed separatrix remains an exact orbit after perturbation.