Two-loop scalar diagrams from string theory

Abstract

We show how to obtain correctly normalized expressions for the Feynman diagrams of Φ 3 theory with an internal U( N) symmetry group, starting from tachyon amplitudes of the open bosonic string, and suitably performing the zero-slope limit by giving an arbitrary mass m to the tachyon. In particular we present explicit results for the two-loop amplitudes of Φ 3 theory, in preparation for the more interesting case of multiloop amplitudes of non-abelian gauge theories.