Kurkela Aleksi, Mazeliauskas Aleksas, Paquet Jean-François, Schlichting Sören, Teaney Derek
Theoretical Physics Department, CERN, Geneva, Switzerland and Faculty of Science and Technology, University of Stavanger, 4036 Stavanger, Norway.
Institut für Theoretische Physik, Universität Heidelberg, 69120 Heidelberg, Germany and Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA.
Phys Rev Lett. 2019 Mar 29;122(12):122302. doi: 10.1103/PhysRevLett.122.122302.
High-energy nuclear collisions produce a nonequilibrium plasma of quarks and gluons which thermalizes and exhibits hydrodynamic flow. There are currently no practical frameworks to connect the early particle production in classical field simulations to the subsequent hydrodynamic evolution. We build such a framework using nonequilibrium Green's functions, calculated in QCD kinetic theory, to propagate the initial energy-momentum tensor to the hydrodynamic phase. We demonstrate that this approach can be easily incorporated into existing hydrodynamic simulations, leading to stronger constraints on the energy density at early times and the transport properties of the QCD medium. Based on (conformal) scaling properties of the Green's functions, we further obtain pragmatic bounds for the applicability of hydrodynamics in nuclear collisions.
高能核碰撞产生由夸克和胶子组成的非平衡等离子体，该等离子体热化并呈现流体动力学流动。目前尚无实用框架可将经典场模拟中的早期粒子产生与随后的流体动力学演化联系起来。我们利用在量子色动力学动力学理论中计算出的非平衡格林函数构建了这样一个框架，以便将初始能量 - 动量张量传播到流体动力学阶段。我们证明，这种方法可以很容易地纳入现有的流体动力学模拟中，从而对早期的能量密度和量子色动力学介质的输运性质产生更强的约束。基于格林函数的（共形）标度性质，我们进一步获得了流体动力学在核碰撞中适用性的实用界限。
