Formula_12907

\[S=\sum_{n=0}^{\infty} \frac{(-i)^{n}}{n !} \int d x_{1} \ldots d x_{n} \Phi^{n}\left(x_{1}, \ldots, x_{n}\right): \varphi\left(x_{1}\right) \ldots \varphi\left(x_{n}\right):\]