Exponentiation of Multiparticle Amplitudes in Scalar Theories

Abstract

It is argued that the amplitudes of the production of $n$ soft scalar particles by one or a few energetic ones in theories like $λϕ^4$ has the exponential form, $A_n\propto\sqrt{n!}\exp[{1\overλ}F(λn,ε)]$, in the regime $λ\to 0$, $λn={fixed}$, $ε={fixed}$, where $ε$ is the typical kinetic energy of outgoing particles. Existing results support this conjecture. Several new analytical and numerical results in favor of the exponential behavior of multiparticle amplitudes are presented.