Hamiltonian form of extended cubic-quintic nonlinear Schrödinger equation  in a nonlinear Klein-Gordon model.

Sedletsky, Yu V; Gandzha, I S · Phys Rev E · 2022

basic_science · Level V

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Abstract

We derive an extended cubic-quintic nonlinear Schrödinger equation with Hamiltonian structure in a nonlinear Klein-Gordon model with cubic-quintic nonlinearity. We use the nonlinear dispersion relation to properly take into account the input of high-order nonlinear effects in the Hamiltonian perturbation approach to nonlinear modulation. We demonstrate that changing the balance between the cubic and quintic nonlinearities has a significant effect on the stability of unmodulated wave packets to long-wave modulations.