Quasilocal definitions of stress-energy–momentum—that is, in the form of boundary densities (in lieu of local volume densities) — have proven generally very useful in formulating and applying conservation laws in general relativity. In this Essay, we take a basic look into applying these to cosmology, specifically using the Brown–York quasilocal stress-energy–momentum tensor for matter and gravity combined. We compute this tensor and present some simple results for a flat FLRW spacetime with a perfect fluid matter source. We emphasize the importance of the vacuum energy, which is almost universally underappreciated (and usually “subtracted”), and discuss the quasilocal interpretation of the cosmological constant.

中文翻译：

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宇宙学中的准局域守恒定律：初看

应力-能量-动量的准局部定义——即以边界密度的形式（代替局部体积密度）——已证明在广义相对论中制定和应用守恒定律通常非常有用。在这篇文章中，我们对将这些应用于宇宙学进行了基本的研究，特别是使用布朗-约克准局域应力-能量-动量张量来结合物质和重力。我们计算了这个张量，并给出了具有完美流体物质源的平坦 FLRW 时空的一些简单结果。我们强调真空能量的重要性，它几乎普遍被低估（并且通常被“减去”），并讨论了宇宙学常数的准局域解释。