标题： 关于完美能量张量的流动 显示英文标题

标题： On the flow of perfect energy tensors

摘要： 获得了一个单位类时矢量场$u$成为散度为零的理想流体能量张量的单位速度的必要且充分条件。 这种对保守理想流体的明显运动学描述需要考虑由$u$的微分伴随量定义的十八个类别。 对于这些类别中的每一个，我们得到标记保守能量张量流动的附加约束条件，并得到完成守恒方程解的函数对$\{\rho,p\}$，即能量密度和压强。 显示英文摘要

摘要： The necessary and sufficient conditions are obtained for a unit time-like vector field $u$ to be the unit velocity of a divergence-free perfect fluid energy tensor. This plainly kinematic description of a conservative perfect fluid requires considering eighteen classes defined by differential concomitants of $u$. For each of these classes, we get the additional constraints that label the flow of a conservative energy tensor, and we obtain the pairs of functions $\{\rho,p\}$, energy density and pressure, which complete a solution to the conservation equations.