Multiscalar amplitudes to all orders in perturbation theory

Abstract

A method for calculating loop amplitudes at the multiboson threshold is presented, based on Feynman-diagram techniques. We explicitly calculate the one-loop amplitudes in both ${\varphi }^4$-symmetric and broken symmetry cases, using dimensional regularization. We argue that, to all orders in the perturbation expansion, the unitarity-violating behaviour of the tree-order amplitudes persists.

Comments: 7 pages, Latex, CERN-TH.6852/93