论文标题
评论“具有外部压力的流体中类似Schwarzschild的几何形状”
Comment on "Analog Schwarzschild-like geometry in fluids with external pressure''
论文作者
论文摘要
在参考[1]，发现了Schwarzschild和Reissner-NordströmSpaceTimes的（不仅与共同相关的）模型。背景非相关流体流动是由不受线性波动影响的外体力量维持的。沿着不同的途径，通过将外力建模为外部压力的梯度，以〜\ cite {bilic}的形式显示出声速已显着修改。这种有效的声音速度与连续性方程式不一致。在此评论中，我们分析了这两个矛盾的结论。我们首先表明，通过参考文献中给出的各种原理引入外力的启发式理由。 [2]在概念上是不正确的。然后，通过适当地添加外力，我们表明[1]中的结论仍然有效。
In Ref. [1], exact (not only conformally related) analogue models for the Schwarzschild and Reissner-Nordström spacetimes were found. The background non-relativistic fluid flow was sustained by an external body force which is not affected by the linearised fluctuations. Following a different route, by modelling the external force as the gradient of an external pressure, it was shown in~\cite{bilic} that the speed of sound is significantly modified. This effective speed of sound turns out to be inconsistent with the continuity equation. In this comment we analyse these two contradictory conclusions. We first show that the heuristic justification for the introduction of the external force via a variational principle given in Ref. [2] is conceptually incorrect. Then, by adding the external force appropriately, we show that the conclusions in [1] remain valid.
