In this work, it has been indicated that the key features requisite for preserving causality and stability of the popularly existing relativistic hydrodynamic theories, can be translated into each other. It has been shown here, that a generic ‘fluid frame transformation’ including all orders of gradient corrections can recast a stable-causal hydrodynamic theory that (i) only includes fundamental fluid variables (velocity and temperature) but requires to be in a general hydrodynamic frame other than the Landau or Eckart, to a theory that is (ii) pathology free in Landau frame but needs newer degrees of freedom. Since frame choice provides the first principle field definitions and degrees of freedom indicate the number of conserved quantities, the causality and stability of a theory seem to require a consensus between the two unless the derivative correction goes to infinity. The key finding of this work is to indicate a connection between these different formalisms, that lead to a causal and stable hydrodynamic theory.

中文翻译：

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相对论流体力学理论中的因果关系和稳定性——一个必须忍受的选择


在这项工作中，已经表明，保持普遍存在的相对论流体动力学理论的因果关系和稳定性所必需的关键特征可以相互转化。这里已经表明，包括所有阶次梯度校正的通用“流体框架变换”可以重塑稳定因果流体动力学理论，该理论（i）仅包括基本流体变量（速度和温度），但需要处于一般流体动力学中兰道或埃卡特以外的框架，到一种理论，该理论在兰道框架中是无病理学的，但需要更新的自由度。由于框架选择提供了第一主域定义，而自由度表示守恒量的数量，因此理论的因果关系和稳定性似乎需要两者之间达成共识，除非导数校正达到无穷大。这项工作的主要发现是指出这些不同形式之间的联系，从而产生因果且稳定的流体动力学理论。