RPMC simulations for the coagulation test with the runaway kernel (Eq. (70)) using the bucketing scheme. The RPMC simulation runs use n = 2048 and n = 65 536 representative particles, respectively, and a particle regime threshold of N_th = 10. The dimensionless threshold mass of m_th = 10⁷, marking the point where runaway growth ensues, is indicated by the dotted red horizontal lines, and the dashed orange lines indicates the representative particle mass M/(nN_th) at which swarms are split up into individual particles. The plots show time series of histograms of the mass-weighted particle number density with bin counts colour-encoded on a logarithmic scale. The runaway particle is shown separately (red curve). Results have been averaged over 10 runs; the shaded surroundings of the red curve indicate the error bounds of the runaway particle mass.