Pauli–Villars regularization

Pauli–Villars regularization consists of introducing a fictitious mass term. For example, we would replace a photon propagator \frac{1}{k^2 + i \epsilon} , by \frac{1}{k^2 + i \epsilon} - \frac{1}{k^2 - \Lambda^2+ i \epsilon} , where \Lambda can be thought of as the mass of a fictitious heavy photon, whose contribution is subtracted from that of an ordinary photon. == See also ==