\LARGE(\int\prod_{{\bf R}}d\bar{{\bf u}}({\bf R})d\bar{{\bf P}}({\bf R})
\nonumber\\
&&\times \exp\left[
- -\sum\frac{1}{2M}{\bf P}({\bf R})^2
+ -\sum\frac{1}{2M}\bar{{\bf P}}({\bf R})^2
-\frac{1}{4}\sum
[\bar{u}_{\mu}({\bf R})-\bar{u}_{\mu}({\bf R'})]
\Phi_{\mu v}({\bf R}-{\bf R'})