Exact combinatorics of Bern-Kosower-type amplitudes for two-loop φ3 theory Original Research Article

Counting the contribution rate of a world-line formula to Feynman diagrams in (φ3 theory, we explain the idea of how to determine precise combinatorics of Bern-Kosower-like amplitudes derived from a bosonic string theory for N-point two-loop Feynman amplitudes. In this connection we also present a method to derive simple and compact world-line forms for the effective action.