基于耗散相对论流体动力学的QCD临界点附近的动力学密度涨落-临界点处马赫锥的可能命运-
Dynamical Density Fluctuations around QCD Critical Point Based on Dissipative Relativistic Fluid Dynamics-possible fate of Mach cone at the critical point-
摘要：
本文件有两个目的。首先，我们利用耗散相对论流体动力学研究了量子色动力学（QCD）临界点（CP）附近的动力学密度涨落，其中考虑了密度涨落与其它守恒量涨落的耦合。结果表明，在QCD CP中，与密度涨落直接耦合的声模被衰减，而热模则成为真正的软模。在此基础上，我们对QCD CP附近的马赫锥作为CP存在的信号的可能命运进行了推测。其次，我们澄清了所谓的一阶相对论流体动力学方程一般没有问题，以描述流体动力学现象与长波长相反，一个天真的怀疑，而即使是Israel-Stewart方程，一个流行的二阶方程，可能无法描述的流体动力学模式一般取决于弛豫时间的值。
英文摘要：
The purpose of this paper is twofold. Firstly, we study the dynamical density fluctuations around the critical point(CP) of Quantum Chromodynamics(QCD) using dissipative relativistic fluid dynamics in which the coupling of the density fluctuations to those of other conserved quantities is taken into account. We show that the sound mode which is directly coupled to the mechanical density fluctuation is attenuated and in turn the thermal mode becomes the genuine soft mode at the QCD CP. We give a speculation on the possible fate of a Mach cone in the vicinity of the QCD CP as a signal of the existence of the CP on the basis of the above findings. Secondly, we clarify that the so called first-order relativistic fluid dynamic equations have generically no problem to describe fluid dynamic phenomena with long wave lengths contrary to a naive suspect whereas even Israel-Stewart equation, a popular second-order equation, may not describe the hydrodynamic mode in general depending on the value of the relaxation time.
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