Testing ...
Ignore this post. I just want to see if MathJax is working.
$$
\mathcal{G}_{\mathbb{D}_x}(S) =
\begin{cases}
[\:\widehat{a}\,] & \text{ when } S = [\,]\\
S + [\:\widehat{a}\,] & \text{ otherwise}
\end{cases}
$$
Ignore this post. I just want to see if MathJax is working.
$$
\mathcal{G}_{\mathbb{D}_x}(S) =
\begin{cases}
[\:\widehat{a}\,] & \text{ when } S = [\,]\\
S + [\:\widehat{a}\,] & \text{ otherwise}
\end{cases}
$$