An improved Representative Particle Monte Carlo method for the simulation of particle growth

Context. A rocky planet is formed out of the agglomeration around 10 40 cosmic dust particles. As aggregates grow by coagulation, their number decreases. But until they have grown to hundreds kilometres, still remains well above particles a computer model can handle directly. The growth from micrometres planetesimal-sized objects therefore has be modelled using statistical methods, often size distribution functions or Monte Carlo methods. However, when reach planetary masses, must treated individually. This done defining two classes objects: class many small bodies in way, and individual such as one more planets. introduces separation between big objects, but it leaves open how transition treat intermediate sizes. Aims. We aim improve Representative Particle (RPMC) method, which used for study able smoothly many-particle limit into single-particle limit. Results. Our new version RPMC method allows variable swarm making possible refine mass resolution where needed. It swarms consist few numbers particles, includes treatment correctness simplified two-component test case validated with an analytical argument. found retain balance accurately describe runaway growth, confirmed standard constant kernel, linear product kernel tests comparison fiducial non-representative simulation.