Classification of radial solutions of energy-critical wave systems
Thomas Duyckaerts, Tristan Roy
TL;DR
This paper advances the understanding of energy-critical, radial, vector-valued wave systems in $\mathbb{R}^3$ by establishing a soliton-resolution framework. It proves that any radial solution with bounded energy along a time sequence decomposes into a linear radiation part plus a finite sum of rescaled stationary states, with the scales well-ordered and stationary-state energies obeying a Pythagorean-type relation. Under an additional structural assumption on the nonlinearity (potential-type case with a finite stationary-set energy spectrum), the authors upgrade this to a continuous-in-time soliton resolution, providing a robust decomposition at all times and a finite-energy conservation principle for the asymptotic states. The approach combines the channels of energy method, a rigidity theorem for nonradiative solutions, nonlinear profile decompositions, and compactness arguments, extending scalar results to vector-valued systems and clarifying the long-time dynamics of energy-critical wave interactions. The work has implications for stability and asymptotic analysis of coupled nonlinear waves and offers a roadmap for investigating higher-dimensional analogs and potential-type nonlinearities in more complex settings.
Abstract
This work concerns a general system of energy-critical wave equations in the Minkowski space of dimension $1+3$. The wave equations are coupled by the nonlinearities, which are homogeneous of degree 5. We prove that any radial solution of the system can be written asymptotically as a sum of rescaled stationary solutions plus a radiation term, along any sequence of times for which the solution is bounded in the energy space. With an additional structural assumption on the nonlinearity, we prove a continuous in time resolution result for radial solutions. The proof of the sequential resolution uses the channel of energy method, as in the scalar case treated by Duyckaerts, Kenig and Merle (Cambridge Journal of Mathematics 2013 and arXiv 1204.0031). The proof of the continous in time resolution is based on new compactness and localization arguments.
