## Existence of solutions to the nonstationary Stokes system in $H_{-\mu }^{2,1}$, $\mu \in (0,1)$, in a domain with a distinguished axis. Part 2. Estimate in the 3d case

### Volume 34 / 2007

#### Abstract

We examine the regularity of solutions to the Stokes system in a neighbourhood of the distinguished axis under the assumptions that the initial velocity $v_0$ and the external force $f$ belong to some weighted Sobolev spaces. It is assumed that the weight is the $(-\mu )$th power of the distance to the axis. Let $f\in L_{2,-\mu } $, $v_0\in H_{-\mu }^1$, $\mu \in (0,1)$. We prove an estimate of the velocity in the $H_{-\mu }^{2,1}$ norm and of the gradient of the pressure in the norm of $L_{2,-\mu }$. We apply the Fourier transform with respect to the variable along the axis and the Laplace transform with respect to time. Then we obtain two-dimensional problems with parameters. Deriving an appropriate estimate with a constant independent of the parameters and using estimates in the two-dimensional case yields the result. The existence and regularity in a bounded domain will be shown in another paper.