# Blow-up of arbitrarily rough critical Besov norms at any Navier-Stokes singularity

18 November 2013
17:00
Gabriel Koch
Abstract
We show that the spatial norm in any critical homogeneous Besov space in which local existence of strong solutions to the 3-d Navier-Stokes equations is known must become unbounded near a singularity. In particular, the regularity of these spaces can be arbitrarily close to -1, which is the lowest regularity of any Navier-Stokes critical space. This extends a well-known result of Escauriaza-Seregin-Sverak (2003) concerning the Lebesgue space $L^3$, a critical space with regularity 0 which is continuously embedded into the spaces we consider. We follow the critical element'' reductio ad absurdum method of Kenig-Merle based on profile decompositions, but due to the low regularity of the spaces considered we rely on an iterative algorithm to improve low-regularity bounds on solutions to bounds on a part of the solution in spaces with positive regularity. This is joint work with I. Gallagher (Paris 7) and F. Planchon (Nice).
• Partial Differential Equations Seminar