提问于：
浏览数：
3452
I see a latex code
```latex{
~~~~a) squared difference:
\begin{equation}
\label{eq.square_diff}
\Phi(q_{\mathbf{p}'}, k_{\mathbf{p}}) = -( q_{\mathbf{p}'} - k_{\mathbf{p}})^2.
\end{equation}
```
But I don't know the meaning of "\~\~\~\~" in the code?
