Srednicki — Quantum Field Theory · Problem 14.1

Canonical Quantization of Scalar Fields — Mark Srednicki

Physics — QFT · feynman-parameter-formula

Problem

Prove Feynman's formula

\frac{1}{A_1 \cdots A_n} = \int dF_n\,(x_1 A_1 + \cdots + x_n A_n)^{-n} , \tag{14.9}

where the integration measure over the Feynman parameters

x_i

\int dF_n = (n-1)!\int_0^1 dx_1 \cdots dx_n\, \delta(x_1 + \cdots + x_n - 1) . \tag{14.10}