2025/08/15 by Chen, Gong, Liu, Jiaqi, Tian, Yuanhong
#Analysis of PDEs (math.AP) #FOS: Mathematics
paper · doi:10.48550/arxiv.2508.11463
We revisit the perturbative theory of infinite dimensional integrable systems developed by P. Deift and X. Zhou \citeDZ-2, aiming to provide new and simpler proofs of some key L^∞ bounds and Lp \empha priori estimates. Our proofs emphasizes a further step towards understanding focussing problems and extends the applicability to other integrable models. As a concrete application, we examine the perturbation of the one-dimensional defocussing cubic nonlinear Schrödinger equation by a localized higher-order term. We introduce improved estimates to control the power of the perturbative term and demonstrate that the perturbed equation exhibits the same long-time behavior as the completely integrable nonlinear Schrödinger equation.