One-loop scalar effective action
= One-loop scalar effective action
{title2=$\Gamma_1[\phi]$}
For a canonically normalized <real scalar field> with potential $V$, the one-loop <quantum effective action> is $\Gamma_1[\phi]=\tfrac12\operatorname{Tr}\log[-\partial^2+V''(\phi)]$, with a suitable <regularization in quantum field theory>. Expanding this <functional determinant> generates <one-particle-irreducible Feynman diagrams> with arbitrarily many external fields.