Dissipation and Elliptic Flow at Relativistic Energies

We compare elliptic flow evolution from ideal hydrodynamics and covariant parton transport theory, and show that, for conditions expected at RHIC, dissipation significantly reduces elliptic flow even for extreme parton cross sections and/or densities σgg×dN/dη(b=0)~45 mb×1000. The difference between transport and hydrodynamic elliptic flow is established rather early during the evolution of the system, but the buildup of elliptic flow is insensitive to the choice of the initial (formation or thermalization) time in both models.