Squeezed bispectrum in the $\delta N$ formalism: local observer effect in field space
Squeezed bispectrum in the $\delta N$ formalism: local observer effect in field space
复制标题
$delta N$ 形式中的压缩双谱：场空间中的局部观察者效应
DOI：
10.1088/1475-7516/2017/02/021
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Vincent Vennin
中科院分区：
文献类型：
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作者：
Yuichiro Tada;Vincent Vennin
未来银河系测量非高斯性的前景要求开发计算原始宇宙学扰动双谱的可靠技术。在本文中，我们提出了一种计算多场膨胀中压缩双谱的新方法。通过使用δN形式，我们的框架揭示了最近指出的全球观察者和本地观察者的压缩双谱之间的差异，同时允许计算两者。特别是对当地观察者来说，压缩的双谱被发现在单场充气中消失了。此外，我们的框架允许人们超越近乎等边(“小等级”)的限制，并自动包括不需要单独计算的内在非高斯性。给出了该方法的显式计算程序，并用几个例子进行了说明。
The prospects of future galaxy surveys for non-Gaussianity measurements call for the development of robust techniques for computing the bispectrum of primordial cosmological perturbations. In this paper, we propose a novel approach to the calculation of the squeezed bispectrum in multiple-field inflation. With use of the δ N formalism, our framework sheds new light on the recently pointed out difference between the squeezed bispectrum for global observers and that for local observers, while allowing one to calculate both. For local observers in particular, the squeezed bispectrum is found to vanish in single-field inflation. Furthermore, our framework allows one to go beyond the near-equilateral (" small hierarchy") limit, and to automatically include intrinsic non-Gaussianities that do not need to be calculated separately. The explicit computational programme of our method is given and illustrated with a few examples.