论文标题
两个定理用于相对论水动力学的梯度扩展
Two theorems for the gradient expansion of relativistic hydrodynamics
论文作者
论文摘要
这封信致力于提供有关相对论流体动力学梯度扩展的两个陈述的证明。第一个陈述是\ textIt {横向导数的排序与非统一流体的梯度膨胀无关。第二个陈述是\ textIt {可以在共形流体的梯度膨胀中消除Weyl协变量的纵向投影}。第二个语句不适用于曲率张量。在共形的情况下，我们知道Weyl协变量的顺序与梯度扩张无关。
This letter is dedicated to providing proof of two statements concerning the gradient expansion of relativistic hydrodynamics. The first statement is that \textit{the ordering of transverse derivatives is irrelevant in the gradient expansion of a non-conformal fluid}. The second statement is that \textit{the longitudinal projection of the Weyl covariant derivative can be eliminated in the gradient expansion of a conformal fluid}. This second statement does not apply to curvature tensors. In the conformal case, we know that the ordering of Weyl covariant derivatives is irrelevant in the gradient expansion.
