Anderson localized states for the nonlinear Maryland model on $\mathbb{Z}^d$
Shihe Liu, Yunfeng Shi, Zhifei Zhang
TL;DR
This work addresses nonlinear Anderson localization for a Maryland quasi-periodic model on $\mathbb{Z}^d$ by diagonalizing the linear Maryland operator and applying a Craig–Wayne–Bourgain (CWB) framework. The authors construct time-quasi-periodic, spatially exponentially decaying localized states for the nonlinear Schrödinger equation $i\partial_t u=Hu+\delta|u|^{2p}u$ in the regime of small $\varepsilon$ and $\delta$ with Diophantine frequency $\alpha$, starting from a finite set of localized linear eigenfunctions. Key contributions include a large deviation theorem for Green's functions across multiple scales, precise eigenvalue separation estimates for the unbounded Maryland potential, and a nonlinear Lyapunov–Schmidt/Nash–Moser scheme that yields quasi-periodic localized solutions with frequencies near the linear eigenvalues. This work extends Anderson localization to nonlinear Maryland-type models in higher dimensions and provides a robust analytical framework that blends spectral analysis with multi-scale probabilistic techniques, delivering both existence and quantitative decay properties of nonlinear localized states. The results have potential implications for understanding interacting quantum systems in quasi-periodic disordered media and for the broader study of nonlinear dynamics in almost-periodic settings.
Abstract
In this paper, we investigate Anderson localization for a nonlinear perturbation of the Maryland model $H=\varepsilonΔ+\cotπ(θ+j\cdotα)δ_{j,j'}$ on $\mathbb{Z}^d$. Specifically, if $\varepsilon,δ$ are sufficiently small, we construct a large number of time quasi-periodic and space exponentially decaying solutions (i.e., Anderson localized states) for the equation $i\frac{\partial u}{\partial t}=Hu+δ|u|^{2p}u$ with a Diophantine $α$. Our proof combines eigenvalue estimates of the Maryland model with the Craig-Wayne-Bourgain method, which originates from KAM theory for Hamiltonian PDEs.
