2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/192139We investigate entropy production for an expanding system of particles and resonances with isospin symmetry -- in our case pions and $ρ$ mesons -- within the framework of relativistic kinetic theory. A cascade code to simulate the kinetic equations is developed and results for entropy production and particle spectra are presented.17 pages, 10 ps-figures included, only change: preprint number addedHigh Energy Physics - Phenomenologytext