Optimal blowup stability for three-dimensional wave maps
Roland Donninger, David Wallauch
TL;DR
The paper proves the asymptotic stability of the explicit corotational self-similar blowup $U_*^T$ for the 3+1 dimensional wave maps equation into $b S^3$, under perturbations small in the fractional Sobolev norm at the critical level. It achieves this by recasting the problem in similarity coordinates, linearizing around the self-similar profile, and developing a spectral/semigroup framework for the resulting radial equation in five dimensions. A detailed resolvent construction and a suite of Strichartz estimates in fractional Sobolev spaces, together with a projection that isolates the unstable eigenmode, enable a fixed-point argument to control the nonlinear evolution in a norm that captures the self-similar blowup profile. The work advances the understanding of blowup stability in energy-supercritical geometric wave equations by obtaining optimal, fractional-regularity Strichartz estimates in the corotational setting. These techniques provide a robust analytic blueprint for addressing similar stability problems in dispersive geometric PDEs with self-similar blowup.
Abstract
We study corotational wave maps from $(1+3)$-dimensional Minkowski space into the three-sphere. We establish the asymptotic stability of an explicitly known self-similar wave map under perturbations that are small in the critical Sobolev space. This is accomplished by proving Strichartz estimates for a radial wave equation with a potential in similarity coordinates. Compared to earlier work, the main novelty lies with the fact that the critical Sobolev space is of fractional order.
