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Blow-up and strong instability of standing waves for the NLS-$δ$ equation on a star graph (1908.07122v2)
Published 20 Aug 2019 in math.AP and math.SP
Abstract: We study strong instability (by blow-up) of the standing waves for the nonlinear Schr\"odinger equation with $\delta$-interaction on a star graph $\Gamma$. The key ingredient is a novel variational technique applied to the standing wave solutions being minimizers of a specific variational problem. We also show well-posedness of the corresponding Cauchy problem in the domain of the self-adjoint operator which defines $\delta$-interaction. This permits to prove virial identity for the $H1$- solutions to the Cauchy problem. We also prove certain strong instability results for the standing waves of the NLS-$\delta'$ equation on the line.