Construction of periodic solutions of multi-dimensional nonlinear wave equations with unbounded perturbation
Huining Xue, Zuhong You, Xiaoping Yuan
TL;DR
The paper advances the persistence theory for nonlinear wave equations by extending the Craig-Wayne-Bourgain framework to multi-dimensional NLW with unbounded, derivative-type perturbations. It combines a lattice formulation with a Lyapunov-Schmidt decomposition into P- and Q-equations, and develops a Newton-type analytic scheme for the P-equations while deriving precise Q-equation amplitudes and frequency corrections. A key technical contribution is a separation lemma for unbounded perturbations under generalized Diophantine conditions, together with finite- and infinite-step measure estimates that yield a Cantor-type set of parameters with full asymptotic measure as the perturbation parameter vanishes. The results provide Gevrey-smooth periodic solutions with explicit frequency shifts $\lambda^{2}=|m_{0}|^{2}+\rho+\tfrac{3}{4}\langle m_{0}\rangle^{\alpha} p_{0}^{2}\varepsilon^{2}+O(\varepsilon^{17/8})$, establishing robustness of periodic responses in higher-dimensional NLW under fractional-derivative perturbations.
Abstract
By applying the Craig-Wayne-Bourgain (CWB) method, we establish the persistence of periodic solutions to multi-dimensional nonlinear wave equations (NLW) with unbounded perturbation.
