\begin{equation*}
\vec{\kappa}^{(eq)} = \Big( \rho, 0, 0, 2 \rho c_s^2, 0 \Big)^T.
\end{equation*} 

%\begin{equation*}
%\vec{\kappa}^{(eq)} = \begin{pmatrix}\rho \\
%0\\
%0\\
%2 \rho c_s^2 \\
%0 \end{pmatrix}.
%\end{equation*} 
