Theory of dissipative fluid dynamics (B01)

流体力学可以表示为克努森数Kn的幂次展开，即微观长度尺度与宏观长度尺度之比。然而，由于重离子碰撞产生的体系体积小，流体动力场梯度大，因此存在Kn不小的区域，限制了流体动力学的适用性。我们使用矩量方法系统地改进了耗散流体动力学理论，并通过在Kn的幂展开中加入高阶项和使用各向异性参考状态来扩展其适用范围。我们通过比较玻尔兹曼方程的解来控制我们的近似。

Fluid dynamics can be formulated as an expansion in powers of the Knudsen number Kn, the ratio of a microscopic to a macroscopic length scale. However, since the systems created in heavy-ion collisions are small and feature large gradients of the fluid-dynamical fields, there are regions where Kn is not small, limiting the applicability of fluid dynamics. We use the method of moments to systematically improve the theory of dissipative fluid dynamics and extend its range of applicability, by including higher-order terms in, and by using an anisotropic reference state for, the expansion in powers of Kn. We control our approximations by comparison to solutions of the Boltzmann equation.