Transport coefficients of a unitarized pion gas

The latest experimental results in relativistic heavy-ion collisions show that the matter there produced requires transport coefficients because of the important collective properties found. We review the theoretical calculation of these transport coefficients in the hadron side at low temperatures by computing them in a gas composed of low energy pions. The interaction of these pions is taken from an effective chiral theory and further requiring scattering unitarity. The propagation of D and D ∗ mesons in the thermalized pion gas is also studied in order to extract the heavy quark diffusion coefficients in the system.