Title: Possible existence of time machines in a five-dimensional spacetime Show Chinese title

Title: 五维时空内时间机器可能存在的问题

Abstract: The idea of constructing a time machine is not new and even received a boost thanks to the realization that a traversable wormhole could be converted to a time machine. It was shown in a recent paper that the time-travel paradoxes can be avoided by assuming the existence of two or more histories or parallel timelines. Accordingly, we start with a physically acceptable model, a spacetime that is anti-de Sitter due to an extra time-like dimension. This model allows the existence of closed time-like curves, as well as two different histories, thereby suggesting a possible avoidance of the time-travel paradoxes. By assuming that the extra dimension is independent of the radial coordinate, the wormhole retains its basic geometric properties regardless of its location. Show Chinese abstract

Abstract: 构造时间机器的想法并不新鲜，甚至由于实现了可以通过虫洞转换为时间机器而得到了推动。 最近的一篇论文表明，通过假设存在两个或多个历史或平行时间线，可以避免时间旅行悖论。 因此，我们从一个物理上可接受的模型开始，即由于额外的时间维度导致的反德西特时空。 该模型允许闭合类时曲线的存在，以及两个不同的历史，从而暗示了可能避免时间旅行悖论。 通过假设额外维度独立于径向坐标，无论虫洞位于何处，虫洞都会保留其基本几何特性。