Existence of multi-solitons with any parameters for the 5D energy critical wave equation
Yvan Martel, Frank Merle
TL;DR
This work proves the existence of multi-soliton solutions for the energy-critical focusing wave equation in dimension five with arbitrary numbers of solitons and parameter choices, addressing the challenge of algebraic soliton decay through a dimension-aware energy method. A refined approximate solution, together with a modulation and bootstrap framework, yields precise control of soliton interactions and the asymptotic behavior $\nabla u(t) \to \sum_k \nabla W_k^\infty$ as $t\to+\infty$. The authors also extend inelasticity results to general multi-soliton configurations under a non-vanishing interaction condition, employing a channel-of-energy analysis for the radial linear wave equation to show non-purity of the solution backward in time. Together, these results advance the understanding of multi-soliton dynamics, stability, and potential soliton-resolution phenomena in high-dimensional critical wave equations.
Abstract
For the focusing, energy critical wave equation in dimension 5, we construct multi-solitons with any number of solitons, any choice of signs, speeds, scaling parameters and translation parameters. This requires to revisit in depth previous constructions of multi-solitons based on a unidirectional approach, to fully take into account the dimension of the space and the possibility for solitons to move in any direction. Then, as a consequence of this more general construction and of the arguments developed in a previous article, the inelastic nature of any collision of solitons is proved under a non-cancellation assumption on the parameters.
