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arXiv · 2610.16564

Long-time asymptotics for the focusing coupled Kundu-Eckhaus equation

Tianwei Qiu·Zhen Wang
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Abstract

The focusing coupled Kundu-Eckhaus (CKE) equation extends the coupled nonlinear Schrödinger (CNLS) equation by adding quintic and derivative nonlinearities. We study the Cauchy problem for the focusing CKE equation with Schwartz initial data under the assumption of no discrete spectrum and no spectral singularities on the real axis. Based on the gauge equivalence between the focusing CKE and CNLS equations, we analyze the associated $3\times3$ matrix Riemann-Hilbert problem by the Deift-Zhou nonlinear steepest descent method. By establishing joint error estimates for the CNLS solution and the gauge phase, we obtain a uniform long-time asymptotic formula for the dispersive radiation of the CKE equation with an $O(t^{-1}\log t)$ remainder in bounded velocity cones.

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Tianwei Qiu, Zhen Wang. 2026-10-12. Long-time asymptotics for the focusing coupled Kundu-Eckhaus equation. https://arxiv.org/abs/2610.16564

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