$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.12
\begin{equation} \begin{gathered}\label{equation:thin-in-correspondence2} \xymatrix@R =50pt@C=50pt{ \operatorname{\partial \Delta }^{n} \ar [r] \ar [d] & \operatorname{\mathcal{C}}_{\varphi /} \ar [d] \\ \Delta ^{n} \ar@ {-->}[ur] \ar [r] & \operatorname{\mathcal{C}}_{\varphi _0/} } \end{gathered} \end{equation}