The partial null conditions and global smooth solutions of the nonlinear wave equations on $\mathbb{R}^d\times\mathbb{T}$ with $d=2,3$

TL;DR

This paper proves the global existence of smooth solutions for certain nonlinear wave equations on product spaces, under partial null conditions, using Fourier analysis, decay estimates, and energy methods, with applications to fluid dynamics and membrane equations.

Contribution

It introduces a novel approach combining Fourier mode decomposition and energy estimates to analyze nonlinear wave equations on product spaces with partial null conditions.

Findings

Global smooth solutions under partial null conditions

Almost global solutions when conditions are violated

Applications to fluid and membrane equations

Abstract

In this paper, we investigate the fully nonlinear wave equations on the product space $\mathbb{R}^3\times\mathbb{T}$ with quadratic nonlinearities and on $\mathbb{R}^2\times\mathbb{T}$ with cubic nonlinearities, respectively. It is shown that for the small initial data satisfying some space-decay rates at infinity, these nonlinear equations admit global smooth solutions when the corresponding partial null conditions hold and while have almost global smooth solutions when the partial null conditions are violated. Our proof relies on the Fourier mode decomposition of the solutions with respect to the periodic direction, the efficient combinations of time-decay estimates for the solutions to the linear wave equations and the linear Klein-Gordon equations, and the global weighted energy estimates. In addition, an interesting auxiliary energy is introduced. As a byproduct, our results can be applied to the 4D irrotational compressible Euler equations of polytropic gases or Chaplygin gases on $\mathbb{R}^3\times\mathbb{T}$, the 3D relativistic membrane equation and the 3D nonlinear membrane equation on $\mathbb{R}^2\times\mathbb{T}$.