强作用量子系统的非平衡输运及流体力学集体模式研究

The non-equilibrium transport properties and hydrodynamic collective modes of strongly interacting quantum systems are the central topics in contemporary physic community. Different from the weakly interacting quasi-particle viewpoint of the perturbative QCD, the matter produced in ultra-relativistic heavy ion collisions manifests a strongly interacting near-ideal liquid characteristic. As an indication of strong interaction, the ratio of shear viscosity to entropy density can be very small and has attracted much attention. Based on the string theory-AdS/CFT, the low bound conjecture 1/(4\pi) has been proposed. Due to the scale invariance and universal properties, it is expected the cold Fermi atomic gas experiments can explore the common physics hidden in the relativistic heavy ion collisions. Especially, the interaction strength between the atoms can be artificially controlled by tuning the extra magnetic field. The non-relativistic ultra-cold atomic strongly interacting Fermi gas can be used to model the relativistic nuclear matter produced in the heavy ion collisions. .We will study the non-equilibrium transport properties of low viscous strongly interacting fermions. Hydrodynamic behavior of strongly interacting fermions and the effects of shear viscosity on the collective excitation modes will be investigated. Meanwhile, we will further explore the effects of viscosity on the nonlinear Landau damping and dispersion transport, which is related with the strongly interacting quantum many-body systems.

强作用量子系统的非平衡输运性质、流体力学激发模式相关物理是当今国际物理学界关注的焦点问题。与弱作用准粒子图象的微扰QCD 理论预言不同，相对性重离子碰撞（RHIC）实验揭示产生了低粘滞的强耦合物质，剪切粘滞系数与熵密度之比非常小，即系统体现近"理想流体"的性质。基于弦论的Ads/CFT 对应关系，国际物理学界给出了强作用量子液体的低粘滞下限1/(4\pi)。由于标度不变性和普适规律的要求，理论界认为可用非相对论性的冷原子气体探索近理想流体系统的流体力学行为。本课题紧密地与当前超冷费米原子气实验、理论的研究前沿相结合，分析低粘滞强作用费米子系统的非平衡输运；研究与普适性相关的强作用量子系统的流体力学激发模式；并探索与非线性物理相关的朗道阻尼及扩散输运的低粘滞效应。

按项目申请书进行了研究，并取得了预期的研究成果。.主要研究内容是探索强相互作用物质的非平衡输运及低粘滞流体的流体力学性质。核物质是典型的强作用物质，探索介子σ-ω混合耦合项对非对称性及对称性核物质的热力学性质及相图的重要影响[1]。.察了幺正费米子气体中的剪刀模式，用理论推导及数值方法结果分析了速度场的涡旋形分布特征，提示粘滞性质对其重要作用[2]。基于粘滞色流体力学框架推导出了包含剪切粘滞系数的夸克胶子等离子体的胶子极化张量，考察了粘滞性质对穿过夸克胶子等离子体的快速部分子的能量损失情况[3]。重部分子穿过夸克胶子等离子体会激发介质极化及色场涨落，这种效应反过来会对部分子产生拖拽力。在粘滞流体力学框架下考察了色场涨落效应的影响[4]。在动理论的框架下，利用Bhatnagar-Gross-Krook (BGK) 碰撞核推导出了夸克胶子等离子体的介电容率及磁导率，并进一步得到了夸克胶子等离子体的介电常数。结果表明，与无碰撞情况相反，在一些频率范围里可能存在负折射率[5]。