Corrected the definition of the Balsara switch in the theory file.

The old one (coming from the gadget-2 paper) had the wrong numerator.



Former-commit-id: 963ef8e0320b242e5452877a65039a0d2f5a05c0

theory/latex/swift.tex

@@ -684,7 +684,7 @@ usually takes value in the range $[0.5, 2]$. The Balsara switch $(f_i+f_j)$ is b
 pre-computed in the density loop:
 
 \begin{eqnarray*}
- f_i &=& \frac{|\vec\nabla \times \vec{v}_i|}{|\vec\nabla \cdot \vec{v}_i| + |\vec\nabla \times \vec{v}_i| +
+ f_i &=& \frac{|\vec\nabla \cdots \vec{v}_i|}{|\vec\nabla \cdot \vec{v}_i| + |\vec\nabla \times \vec{v}_i| +
 10^{-4}\frac{c_j}{h_j}} \\
  \vec\nabla \times \vec{v}_i &=& -\frac{1}{\rho_i}\sum_j m_j (\vec{v}_j - \vec{v}_i)\times
 \vec{\nabla_r}W(\vec{r}_{ij}, h_i) \\