  Two-parameter sets of solutions to the classical field equations in the
massless $\phi^4$ model and SU(2) gauge theory are found, each solution
presumably describing a multi-particle instanton-like transition at high
energy. In the limit of small number of initial particles, the probability of
the transition is suppressed by $\exp(-2S_0)$, where $S_0$ is the instanton
action.

High Energy Physics - Phenomenology