Early time evolution of high-energy heavy-ion collisions

We solve the Yang - Mills equations in the framework of the McLerran - Venugopalan model for small times tau after a collision of two nuclei. An analytic expansion around tau = 0 leads to explicit results for the field strength and the energy - momentum tensor of the gluon field at early times. We then discuss constraints for the energy density, pressure and flow of the plasma phase that emerges after thermalization of the gluon field.