1 Kinetic equilibration from a radiative transport Bin Zhang Arkansas State University 25 th Winter Workshop on Nuclear Dynamics, Big Sky, Montana, February 1-8, 2009 Introduction Longitudinal to transverse pressure ratio Energy density evolution Summary Work supported by the U.S. National Science Foundation under grant No. PHY

String melting scenario increases faster than the default scenario There is a late time increase to above 1. It is caused by on set of transverse expansion Larger parton cross section leads to larger early pressure anisotropy and later transverse expansion Partial thermalization is achieved 2 Introduction: kinetic equilibration Momentum isotropy can be characterized by P L /P T

3 Introduction: radiative transport Initial conditions The reaction rates Isotropic in local rest frame

Longitudinal to transverse pressure ratio 4 competition between expansion and equilibration α s T scaling for elastic with dynamical screening α s T scaling broken by gg↔ggg processes. Approximate α s scaling due to chemical equilibration Evolution from thermal initial conditions

5 Longitudinal to transverse pressure ratio same asymptotic evolution from same initial ε memory effect reflected in difference larger α, smaller relaxation time larger initial ε, smaller relaxation time Comparison with transverse initial conditions

6 Energy density evolution early time power law behavior reflects initial isotropy asymptotic power law behavior reflects interactions behavior not sensitive to initial energy density Viscous corrections can not be neglected

7 Summary and outlook Equilibration dominates over expansion at large times. Approximate α s scaling of pressure isotropy with inelastic processes. Pressure isotropy follows asymptotic evolution when memory effect goes away. Energy density evolution has limiting power law behavior. Viscous corrections are present throughout evolution. What will happen with more sophisticated initial conditions? What can one learn with pQCD rates, LPM effect, etc? What are the effects of thermalization on other observables?