答案1
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\dot{\overline{\int_{\mathcal{P}_t} \rho\,dv}} = 0
\]
\end{document}
要按照 OP 所示调整限制,根据 egreg 的提醒,使用\limits
:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\dot{\overline{\int\limits_{\mathcal{P}_t} \rho\,dv}} = 0
\]
\end{document}