关于一般引力理论中的视超光速驱动
About apparent superluminal drives in generic gravity theories
摘要：
众所周知，在GR中存在翘曲驱动器，例如Alcubierre气泡，其实现了明显快于光速的\cite{alcubierre}。由高和瓦尔德\cite{gaowald}得出的结果表明，对于既满足能量守恒条件又满足能量守恒条件的物质来说，这样的旅行是不可能的。由于加洛韦的观点，这一结论有一个推广，它确保了高-瓦尔德的结果是正确的，而不管潜在的引力模型如何，除非在时空中存在至少一条不可扩展的零测地线（零线）。这个命题的证明是基于因果理论的技术，从未被公布。在目前的工作中，这一结果的独立证明，提出了使用Raychaudhuri方程，并避免了几个技术并发症沿文字描述。最后一节讨论了这些断言的一些后果，特别是它们在因果关系问题中的潜在用途。
英文摘要：
As is well known, there exists warp drives in GR, such as the Alcubierre bubbles, which achieve an apparent faster than light travel \cite{alcubierre}. A result due to Gao and Wald \cite{gaowald} suggests that such a travel is unlikely for GR with matter satisfying both the Null Energy and the Null Generic Conditions. There exists a generalization of this statement due to Galloway, that ensures that the Gao-Wald result is true regardless the underlying gravity model, unless there exists at least one inextendible null geodesic with achronal image in the space time (a null line). The proof of this proposition is based on techniques of causal theories, and has never been released. In the present work an independent proof of this result is presented by use of the Raychaudhuri equation, and avoiding several technical complications described along the text. Some consequences of these affirmations are discussed at last section, in particular their potential use in problems of causality.
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