论文标题
Painleve Gullstrand坐标中的宇宙学
Cosmology in Painleve-Gullstrand coordinates
论文作者
论文摘要
宇宙学通常是使用标准共同移动坐标来分析的，其中星系（平均而言，可能是小特殊的速度）“静止”，而“空间”正在扩展。但这只是一个特定的坐标选择。重要的是要意识到，出于某些目的，其他（有时是根本不同）协调选择也可能证明是有用的和有益的，但没有改变基本的物理学。具体而言，在这里，我们将考虑K = 0的空间平坦FLRW宇宙学，但在Painleve-Gullstrand坐标中 - 这些坐标非常明确地不连接：“空间”现在不再扩展，尽管星系之间的距离仍然肯定在增加。在这些Painleve-Gullstrand坐标中工作提供了关于标准宇宙学及其对称性的另一种观点，并且还使其更容易处理宇宙学视野。有了更长的看法，我们希望研究这些painleve-gullstrand坐标最终可能会为理解理想化的FLRW空间偏离大偏差提供更好的框架。我们通过仔细研究Kottler和McVittie的空间来说明这些问题。
Cosmology is most typically analyzed using standard co-moving coordinates, in which the galaxies are (on average, up to presumably small peculiar velocities) "at rest", while "space" is expanding. But this is merely a specific coordinate choice; and it is important to realise that for certain purposes other, (sometimes radically different) coordinate choices might also prove useful and informative, but without changing the underlying physics. Specifically, herein we shall consider the k=0 spatially flat FLRW cosmology but in Painleve-Gullstrand coordinates -- these coordinates are very explicitly not co-moving: "space" is now no longer expanding, although the distance between galaxies is still certainly increasing. Working in these Painleve-Gullstrand coordinates provides an alternate viewpoint on standard cosmology, and the symmetries thereof, and also makes it somewhat easier to handle cosmological horizons. With a longer view, we hope that investigating these Painleve-Gullstrand coordinates might eventually provide a better framework for understanding large deviations from idealized FLRW spacetimes. We illustrate these issues with a careful look at the Kottler and McVittie spacetimes.
