标题： 从弗拉姆-爱因斯坦-罗森桥到可穿越虫洞的现代复兴 显示英文标题

标题： From the Flamm-Einstein-Rosen bridge to the modern renaissance of traversable wormholes

摘要： 我们研究了多重连接时空的可能性，包括从Flamm-Einstein-Rosen桥、几何子（geons）到可穿越虫洞的现代复兴。 虫洞物理中的一个基本性质是喉部的扩张条件，它通过爱因斯坦场方程暗示了零能条件的违反。 在修正引力理论的背景下，也已经证明普通物质可以满足能量条件，而支撑这些非标准虫洞几何结构的是高阶曲率项，它们被解释为一种引力流体，从根本上不同于广义相对论中的对应物。 我们探讨了这些几何结构的有趣特性，特别是这些‘奇异时空’的物理属性和特征。 显示英文摘要

摘要： We consider the possibility of multiply-connected spacetimes, ranging from the Flamm-Einstein-Rosen bridge, geons, and the modern renaissance of traversable wormholes. A fundamental property in wormhole physics is the flaring-out condition of the throat, which through the Einstein field equation entails the violation of the null energy condition. In the context of modified theories of gravity, it has also been shown that the normal matter can be imposed to satisfy the energy conditions, and it is the higher order curvature terms, interpreted as a gravitational fluid, that sustain these non-standard wormhole geometries, fundamentally different from their counterparts in general relativity. We explore interesting features of these geometries, in particular, the physical properties and characteristics of these `exotic spacetimes'.