= Rate of strain and vorticity of a Stokeslet
{title2=$e_{ij}=\frac{\mathbf F\cdot\mathbf x}{8\pi\mu r^3}(\delta_{ij}-3x_ix_j/r^2),\quad\boldsymbol\omega=\frac{\mathbf F\times\mathbf x}{4\pi\mu r^3}$}
Differentiating the <Stokeslet> gives its <rate-of-strain tensor> and <vorticity>, displayed above for $r=|\mathbf x|>0$. The pressure is $p=\mathbf F\cdot\mathbf x/(4\pi r^3)$. Integrating the <Newtonian fluid stress tensor> over a sphere enclosing the origin gives traction resultant $-\mathbf F$, fixing the point-force normalization.
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