How do you prove the following commutation relation for the lattice QFT
\begin{equation} [\phi(X),\Pi(y)]=\text{i}a^{-d}\delta_{x,y}\mathbb{I}? \end{equation}
How do you prove the following commutation relation for the lattice QFT
\begin{equation} [\phi(X),\Pi(y)]=\text{i}a^{-d}\delta_{x,y}\mathbb{I}? \end{equation}