“…There is an abundant literature on boundary layer associated with incompressible flows and the related question of vanishing viscosity (see for instance [2,7,47,48,10,40,14,22,46,19,20,8,27,71,31,3,4,32,29,68,1,69,21,57,58,53,55,56,62,23,9,24,18,25,18,25,38,6,15,33,62,39,36,35,12,13,67,61] among many others). We will refrain from surveying the literature here, but emphasize that the boundary layer problem associated with the Navier-Stokes equation is still open and that there is a need to develop tools and methods to tackle it.…”