1. 1 Isotropization of an equilibrating Quark-Gluon Plasma Bin Zhang a, Lie-Wen Chen b, Che-Ming Ko c a Arkansas State University, b Shanghai Jiaotong University, c Texas A&M University 24 th Winter Workshop on Nuclear Dynamics, South Padre Island, April 5-12, 2008 The AMPT model Evolution of bulk properties in the AMPT model Pressure Anisotropy in the AMPT model Summary Work supported by the National Science Foundation under Grant PHY-0554930 (B.Z.) PHY- 0457265, the Welch Foundation Grant No. A-1358 (C.M.K.), the NNSF of China Grant Nos. 10575071 and 10675082, MOE of China project NCET-05-0392, Shanghai Rising-Star Program Grant No. 06QA14024, and the SRF for ROCS, SEM of China (L.W.C.).

2. 2 The AMPT model Lin et al, PRC 72, 064901 (2005)

3. 3 The AMPT model Chen et al.,PLB605,95(2005) Chen et al.,PRC69,031901(2004) Good description of light hadron low p T spectra and elliptic flow

4. 4 Bulk properties in the AMPT model Equation of state can be characterized by P/ε as a function of ε. Active particle contributions are evaluated. default model hadronizes earlier than the string melting model equation of state depends on the parton scattering cross section

5. 5 Bulk properties in the AMPT model hadron / increasesStrange percentage increases

6. 6 Pressure anisotropy in the AMPT model Momentum isotropy can be characterized by P L /P T 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 late transverse expansion Partial thermalization is achieved

7. 7 Summary and Outlook Pressure to energy density ratio in default model is much smaller than the string melting model over a wide range of energy density. Pressure to energy density ratio in the string melting model depends on the partonic cross section. Both longitudinal expansion and transverse expansion can affect pressure anisotropy evolution. The hot and dense matter in the AMPT model does not reach full isotropization. Effects of parton number changing processes, plasma instabilities, hadronization at fixed time, mean field deserve further study.

8. 8 The AMPT model String melting is needed for the description of elliptic flow

9. 9 The AMPT model Rapidity distributions HBT radii

10. 10 Pressure anisotropy in the AMPT model Comoving frame is necessary even for |η s |<0.5 Mid-space-time rapidity region is boost invariant

11. 11 Pressure anisotropy in the AMPT model Parton recombination can introduce dependence on space-time rapidity range

12. 12 Bulk Properties including free streaming hadrons