论文标题
较大的仪表转换，局部坐标和宇宙学可观察力
Large gauge transformations, local coordinates and cosmological observables
论文作者
论文摘要
近年来，在宇宙学中，新型的坐标转换已出现在标准量规变换之上，例如扩张和特殊的保形转换，或导致（保形）费米坐标的一种变换。其中一些可以消除在标准仪转换下不变的效果，还会影响渐近边界条件，从而在我们的宇宙学建模中引入了非平凡的歧义。在简短的说明中，我们指出，这种歧义与我们用来将模型与观察结果（宇宙学可观察的关系）进行比较的数量无关，因为它们在所有这些转换下都是不变的。重要的是，只有当人们考虑到可观察到的所有相对论贡献时，这种不变性才能存在，这在一般文献中并非如此。我们最终还表明，可以通过全球定义的标准量规变换实现保形费米坐标的实际相关性能（距离距离为二阶的FLRW指标）。
In recent years new types of coordinate transformations have appeared in cosmology on top of the standard gauge transformations, such as the dilatations and special conformal transformations, or the ones leading to (conformal) Fermi coordinates. Some of these can remove effects that are invariant under the standard gauge transformations and also affect asymptotic boundary conditions, thus introducing a non-trivial ambiguity in our cosmological modeling. In this short note we point out that this ambiguity is irrelevant for the quantities we use to compare our model with observations -- the cosmological observable relations -- as they are invariant under all of these transformations. Importantly, this invariance holds only if one takes into account all the relativistic contributions to an observable, which is not the case in the literature in general. We finally also show that the practically-relevant property of conformal Fermi coordinates (a FLRW metric up to second order in distance) can be achieved through a globally-defined standard gauge transformation.
