Error analysis of the Lie splitting for semilinear wave equations with finite-energy solutions
Maximilian Ruff, Roland Schnaubelt
TL;DR
The paper addresses rigorous time-integration error analysis for the semilinear wave equation on $\mathbb{R}^3$ with finite-energy data, covering energy-subcritical to energy-critical nonlinearities $\alpha\in[3,5]$. It introduces frequency-filtered Lie splitting and new time-discrete Strichartz estimates, including endpoint results with logarithmic losses, to obtain provable convergence rates in weak norms. For subcritical powers ($\alpha<5$), first-order convergence in $L^2\times\dot H^{-1}$ is shown; at the energy-critical power ($\alpha=5$) a forward-error bound is established, reflecting the dispersive-dominated regime. Additionally, a corrected Lie splitting for the cubic case ($\alpha=3$) with $K=\tau^{-3/2}$ achieves $\tfrac{3}{2}$-order convergence, highlighting the benefit of the correction term and endpoint estimates. Overall, the work provides the first error analysis for scaling-critical dispersive problems with finite-energy data and introduces a robust framework combining discrete Strichartz theory with frequency filtering for NLW time-stepping.
Abstract
We study time integration schemes for $\dot H^1$-solutions to the energy-(sub)critical semilinear wave equation on $\mathbb{R}^3$. We show first-order convergence in $L^2$ for the Lie splitting and convergence order $3/2$ for a corrected Lie splitting. To our knowledge this includes the first error analysis performed for scaling-critical dispersive problems. Our approach is based on discrete-time Strichartz estimates, including one (with a logarithmic correction) for the case of the forbidden endpoint. Our schemes and the Strichartz estimates contain frequency cut-offs.
