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\begin{document}\end{document}
Let
\begin{align}
\mathcal{L}[x]\equiv\mathcal{L}(\phi_{\alpha}(x), \partial_{\mu}\phi_{\alpha}(x)) \label{eq:1}
\end{align}
be Lagrangian density. And let
\begin{align}
\mathcal{H}[x]\equiv\dot{\phi_{\alpha}}(x)\pi_{\alpha}(x)-\mathcal{L}[x] \label{eq:2}
\end{align}
be Hamiltonian density.
\end{document}
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お手数ですが、どこがいけないのか教えてください。