Anisotropic separate universe and Weinberg's adiabatic mode
Anisotropic separate universe and Weinberg's adiabatic mode
复制标题
各向异性分离宇宙和温伯格绝热模式
DOI：
10.1088/1475-7516/2021/07/051
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发表时间：
2021
影响因子：
6.4
通讯作者：
Urakawa Yuko
中科院分区：
文献类型：
--
作者：
Tanaka Takahiro;Urakawa Yuko
在分离论域方法中，一个非均匀论域被重新表述为一组胶合的许多均匀局部斑块。这是梯度展开和δN形式的本质，它们已被广泛用于解决宇宙的长波长演化。在本文中，我们表明，分离论域方法可以被普遍使用，只要所考虑的理论是本地的，并保持空间的同胚不变性。针对这两个条件，我们还阐明了所谓的温伯格绝热模存在的条件。值得注意的是，分离宇宙方法和δN形式主义也适用于大尺度上的剪切模型，也适用于修正的引力理论，接受四维非同态不变性的破坏。广义δN形式使我们能够计算所有的大尺度涨落，包括引力波。我们还讨论了各向异性暴胀和超慢卷暴胀的几个含义。
In the separate universe approach, an inhomogeneous universe is rephrased as a set of glued numerous homogeneous local patches. This is the essence of the gradient expansion and the δN formalism, which have been widely used in solving a long wavelength evolution of the universe. In this paper, we show that the separate universe approach can be generically used, as long as a theory under consideration is local and preserves the spatial diffeomorphism invariance. Focusing on these two conditions, we also clarify the condition for the existence of the so-called Weinberg's adiabatic mode. Remarkably, the separate universe approach and the δN formalism turn out to be applicable also to models with shear on large scales and also to modified theories of gravity, accepting violation of four-dimensional diffeomorphism invariance. The generalized δN formalism enables us to calculate all the large scale fluctuations, including gravitational waves. We also argue several implications on anisotropic inflation and ultra slow-roll inflation.