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arXiv · 2010.00814

Stability of the multi-solitons of the modified Korteweg-de Vries equation

Stefan Le Coz·Zhong Wang
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Abstract

We establish the nonlinear stability of $N$-soliton solutions of the modified Korteweg-de Vries (mKdV) equation. The $N$-soliton solutions are global solutions of mKdV behaving at (positive and negative) time infinity as sums of $1$-solitons with speeds $0<c_1<\cdots< c_N$.The proof relies on the variational characterization of $N$-solitons. We show that the $N$-solitons realize the local minimum of the $(N+1)$-th mKdV conserved quantity subject to fixed constraints on the $N$ first conserved quantities.To this aim, we construct a functional for which $N$-solitons are critical points, we prove that the spectral properties of the linearization of this functional around a $N$-soliton are preserved on the extended timeline, and we analyze the spectrum at infinity of linearized operators around $1$-solitons. The main new ingredients in our analysis are a new operator identity based on a generalized Sylvester law of inertia and recursion operators for the mKdV equation.

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Stefan Le Coz, Zhong Wang. 2020-10-02. Stability of the multi-solitons of the modified Korteweg-de Vries equation. https://doi.org/10.1088/1361-6544%2Fac20a7

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