A system of particles hopping on a line, singly or as merged pairs, and annihilating in groups of three on encounters, is solved exactly for certain symmetrical initial conditions. The functional form of the density is nearly identical to that found in two-body annihilation, and both systems show ∼1/ √t decrease of particle density for large times.

• Received 19 June 1992

DOI:https://doi.org/10.1103/PhysRevA.46.R6140