Title: The shear viscosity of parton matter under two-body scatterings

Speaker: 林子威教授(美国东卡罗来纳大学)

  Prof, Lin received a B.S. in Theoretical Physics from the University ofScience and Technology of China and a Ph,D. in Theoretical Nuclear Physics fromColumbia University. After that he did research at the Lawrence Berkeley NationaLab, Texas A&M University, The Ohio State University, and the NASA MarshalSpace Flight Center. He joined East Carolina University in 2007 and is now aprofessor of physics. His recent research has focused on using Monte Carlotransport models and kinetic theory to study the dynamics of nuclear collisions.

Abstract:

  The shear viscosity of a quark-gluon plasma can be calculated numericallyusing the Green-Kubo relation or analytically using several methods, including theIsrael-Stewart, Navier-Stokes, relaxation time approximation, and Chapman-Enskogmethods. Here we first examine these analytical methods for two-body isotropic andanisotropic scatterings and confirm that the Chapman-Enskog method is the mostaccurate.We then apply the Chapman-Enskog method to study the shear viscosity ofthe parton matter in the center cell of central and mid-central Au+Au collisions at200AGeV and Pb+Pb collisions at 2.76ATeV from a multi-phase transport (AMPTmodel, At the parton scattering cross section of 3 mb that enables the model toreproduce bulk observables including the elliptic fow, the average n/s of the partonmatter is found to be very small, between one to three times 1/(4n). On the otherhand,as a result of using a constant cross section or Debye mass for partorscatterings, the n/s ratio from the AMPT model increases with time (as temperaturedecreases), contrary to the pOCD results that use temperature-dependent Debyemasses. Finally, I show our recent results on improving the parton transport modewith finite-temperature pOCD cross sections, including our new Chapman-Enskocresults for the shear viscosity of a parton matter after including inelastic two-bodyscattetings.

2025-06-03, 15:00

物理学院322