Isotropization in heavy ion collisions in the 2PI formalism

An important question in heavy-ion collisions is how the initial far-from-equilibrium medium evolves and thermalizes while it undergoes a rapid longitudinal expansion. In this presentation, we show how to use the two-particle irreducible (2PI) effective action to address this question, focusing on ${\phi }^4$ scalar theory truncated at three loops. We present numerical results for quantities such as the occupation number, the thermal mass, and the number density.