Shallow-water convergence of the intermediate long wave equation in $L^2$

Fuente: arXiv
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Main Authors: Chapouto, Andreia, Li, Guopeng, Oh, Tadahiro, Zhao, Tengfei
Format: Preprint
Published: 2025
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author Chapouto, Andreia
Li, Guopeng
Oh, Tadahiro
Zhao, Tengfei
author_facet Chapouto, Andreia
Li, Guopeng
Oh, Tadahiro
Zhao, Tengfei
contents We continue our study on the convergence issue of the intermediate long wave equation (ILW) on both the real line and the circle. In particular, we establish convergence of the scaled ILW dynamics to that of the Korteweg-de Vries equation (KdV) in the shallow-water limit at the $L^2$-level. Together with the recent work by the first three authors and D. Pilod (2024) on the deep-water convergence in $L^2$, this work completes the well-posedness and convergence study of ILW on both geometries within the $L^2$-framework. Our proof equally applies to both geometries and is based on the following two ingredients: the complete integrability of ILW and the normal form method. More precisely, by making use of the Lax pair structure and the perturbation determinant for ILW, recently introduced by Harrop-Griffths, Killip, and Vişan (2025), we first establish weakly uniform (in small depth parameters) equicontinuity in $L^2$ of solutions to the scaled ILW, providing a control on the high frequency part of solutions. Then, we treat the low frequency part by implementing a perturbative argument based on an infinite iteration of normal form reductions for KdV.
format Preprint
id arxiv_https___arxiv_org_abs_2511_15905
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Shallow-water convergence of the intermediate long wave equation in $L^2$
Chapouto, Andreia
Li, Guopeng
Oh, Tadahiro
Zhao, Tengfei
Analysis of PDEs
35Q35, 35Q53, 37K10, 76B55
We continue our study on the convergence issue of the intermediate long wave equation (ILW) on both the real line and the circle. In particular, we establish convergence of the scaled ILW dynamics to that of the Korteweg-de Vries equation (KdV) in the shallow-water limit at the $L^2$-level. Together with the recent work by the first three authors and D. Pilod (2024) on the deep-water convergence in $L^2$, this work completes the well-posedness and convergence study of ILW on both geometries within the $L^2$-framework. Our proof equally applies to both geometries and is based on the following two ingredients: the complete integrability of ILW and the normal form method. More precisely, by making use of the Lax pair structure and the perturbation determinant for ILW, recently introduced by Harrop-Griffths, Killip, and Vişan (2025), we first establish weakly uniform (in small depth parameters) equicontinuity in $L^2$ of solutions to the scaled ILW, providing a control on the high frequency part of solutions. Then, we treat the low frequency part by implementing a perturbative argument based on an infinite iteration of normal form reductions for KdV.
title Shallow-water convergence of the intermediate long wave equation in $L^2$
topic Analysis of PDEs
35Q35, 35Q53, 37K10, 76B55
url https://arxiv.org/abs/2511.15905