In this work, we exhibit abstract conditions on a functional space E who insure the existence of a global mild solution for small data in E or the existence of a local mild solution in absence of size constraints for a class of semi-linear parabolic equations, which contains the incompressible Navier-Stokes system as a fundamental example. We also give an abstract criterion toward regularity of the obtained solutions. These conditions, given in terms of Littlewood-Paley estimates for products of spectrally localized elements of $E$, are simple to check in all known cases: Lebesgue, Lorents, Besov, Morrey... spaces. These conditions also apply to non-invariant spaces E and we give full details in the case of some 2-microlocal spaces. The following comments did not show on the first version: This article was written around 1998-99 and never published, because at that time, Koch and Tataru announced their result on well-posedness of Navier-stokes equations with initial data in $BMO^{-1}$. We believe though that some results and counterexamples here are of independent interest and we make them available electronically.
@article{hal-00344728,
author = {Auscher, Pascal and Tchamitchian, Philippe},
title = {Espaces critiques pour le syst\`eme des equations de Navier-Stokes incompressibles},
journal = {HAL},
volume = {1999},
number = {0},
year = {1999},
language = {fr},
url = {http://dml.mathdoc.fr/item/hal-00344728}
}
Auscher, Pascal; Tchamitchian, Philippe. Espaces critiques pour le système des equations de Navier-Stokes incompressibles. HAL, Tome 1999 (1999) no. 0, . http://gdmltest.u-ga.fr/item/hal-00344728/