标题： 在宇宙常数非负的情况下，无限远处的引力辐射 显示英文标题

标题： Gravitational radiation at infinity with non-negative cosmological constant

摘要： 在存在非负宇宙常数$\Lambda\geq 0$的情况下，到达类光无限的引力辐射的存在性得到了解决——即从物理系统中逃逸出来的引力辐射。对于$\Lambda$为零的情况已经得到很好的理解，并且依赖于在无限远处定义的新闻张量场（或新闻函数）的性质。当$\Lambda>0$时，情况截然不同，因为目前尚无具有类似良好性质的“新闻”概念。在本文中，从{\em 潮汐}的观点出发，同时考虑了这两种情况，即考虑到曲率张量的强度（或能量）。为此目的，在{\em 逐渐（辐射）超动量}中使用的基本对象是一个在无限处定义的具有显著性质的因果向量。这导致了一种适用于一般情况且具有$\Lambda\geq 0$的引力辐射的新表征，该表征已被证明在$\Lambda =0$时与基于新闻的标准表征等价。 此结果的含义在$\Lambda >0$时被详细分析。当$\Lambda >0$时，描述了一种构造“新闻张量”的一般方法，提出了渐近对称性的建议，并展示了一个可能在无限远处检测引力辐射的守恒电荷的例子。列出了一系列说明性例子。 显示英文摘要

摘要： The existence of gravitational radiation arriving at null infinity -- i.e. escaping from the physical system -- is addressed in the presence of a non-negative cosmological constant $\Lambda\geq 0$. The case with vanishing $\Lambda$ is well understood and relies on the properties of the News tensor field (or the News function) defined at infinity. The situation is drastically different when $\Lambda>0$ where there is no known notion of `News' with similar good properties. In this paper both situations are considered jointly from a {\em tidal} point of view, that is, taking into account the strength (or energy) of the curvature tensors. The fundamental object used for that purposes in the {\em asymptotic (radiant) super-momentum}, a causal vector defined at infinity with remarkable properties. This leads to a novel characterization of gravitational radiation valid for the general case with $\Lambda\geq 0$ that has been proven to be equivalent, when $\Lambda =0$, to the standard one based on News. The implications of this result are analyzed in some detail when $\Lambda >0$. A general procedure to construct `news tensors' when $\Lambda >0$ is depicted, a proposal for asymptotic symmetries provided, and an example of a conserved charge that may detect gravitational radiation at infinity exhibited. A series of illustrative examples is listed.