引力的最小修正理论：检验广义相对论唯一性的乐园
Minimally modified theories of gravity: a playground for testing the uniqueness of general relativity
摘要：
在最近的一篇论文[1]中，引入了一类新的具有两个局部自由度的引力理论。这些理论的存在显然挑战了广义相对论作为无质量自旋2粒子的独特非线性理论的独特作用。在这里，我们对这些理论进行了全面的分析，目的是（i）理解这些理论是否实际上等同于广义相对论，以及（ii）在这些理论不等同的情况下找到方差的根源。我们发现，一系列看似不同的理论实际上通过了我们能够设计的所有可能的广义相对论（在真空中）等价性测试，包括使用壳层技术分析散射振幅。这些结果得到了补充的观察，唯一的例子，这是明显不等价于广义相对论要么不包含引力子在他们的频谱，或不能保证只包括两个本地自由度，一旦辐射校正考虑。耦合到物质也被认为是：我们表明，耦合这些理论的问题，在一个一致的方式并不像人们所期望的那样简单。不能使用最小耦合以及最直接的非最小耦合。因此，在能够解决物质存在的任何问题之前，有必要找到一个一致的（而且在任何情况下都相当独特的）耦合方案。
英文摘要：
In a recent paper [1], it was introduced a new class of gravitational theories with two local degrees of freedom. The existence of these theories apparently challenges the distinctive role of general relativity as the unique non-linear theory of massless spin-2 particles. Here we perform a comprehensive analysis of these theories with the aim of (i) understanding whether or not these are actually equivalent to general relativity, and (ii) finding the root of the variance in case these are not. We have found that a broad set of seemingly different theories actually pass all the possible tests of equivalence to general relativity (in vacuum) that we were able to devise, including the analysis of scattering amplitudes using on-shell techniques. These results are complemented with the observation that the only examples which are manifestly not equivalent to general relativity either do not contain gravitons in their spectrum, or are not guaranteed to include only two local degrees of freedom once radiative corrections are taken into account. Coupling to matter is also considered: we show that coupling these theories to matter in a consistent way is not as straightforward as one could expect. Minimal coupling, as well as the most straightforward non-minimal couplings, cannot be used. Therefore, before being able to address any issues in the presence of matter, it would be necessary to find a consistent (and in any case rather peculiar) coupling scheme.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
