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arXiv 1006.2771astro-ph.CO
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原始双谱中的振荡:模展开

Oscillations in the Primordial Bispectrum: Mode Expansion

P. Daniel Meerburg

摘要:

我们认为存在的振荡的原始双谱,灵感来自三种不同的宇宙学模型,功能在原始的潜力,共振型非高斯性和偏离标准束戴维斯真空。为了把它们的双谱的约束,逻辑上的第一步是把这些到因式分解的形式,可以通过最近提出的方法的多项式基础上的四面体域扩展。我们调查的可行性,这样的扩展的振荡bispectra,并发现,一个需要越来越多的正交模式函数,以实现显着的相关性之间的扩展和原始频谱作为其频率的函数。为了减少所需的模式的数量,我们提出了一个基础上的傅立叶函数正交化的四面体域。我们表明,使用傅里叶模函数而不是多项式模函数可以产生必要的可因子分解性,只需使用使用多项式模函数重建双谱所需模式总数的1/5。此外,从观测的角度来看,由于模式函数和原始光谱之间的共振效应,扩展具有取决于振荡方向的独特签名。这种效果打开的可能性,以提取有关的双谱的频率以及它的形状,同时考虑只有有限数量的模式的信息。共振效应与重构双谱的相位无关,这表明傅立叶模式提取可能是检测数据中的振荡双谱的有效方法。

英文摘要:

We consider the presence of oscillations in the primordial bispectrum, inspired by three different cosmological models; features in the primordial potential, resonant type non-Gaussianities and deviation from the standard Bunch Davies vacuum. In order to put constraints on their bispectra, a logical first step is to put these into factorized form which can be achieved via the recently proposed method of polynomial basis expansion on the tetrahedral domain. We investigate the viability of such an expansion for the oscillatory bispectra and find that one needs an increasing number of orthonormal mode functions to achieve significant correlation between the expansion and the original spectrum as a function of their frequency. To reduce the number of modes required, we propose a basis consisting of Fourier functions orthonormalized on the tetrahedral domain. We show that the use of Fourier mode functions instead of polynomial mode functions can lead to the necessary factorizability with the use of only 1/5 of the total number of modes required to reconstruct the bispectra with polynomial mode functions. Moreover, from an observational perspective, the expansion has unique signatures depending on the orientation of the oscillation due to a resonance effect between the mode functions and the original spectrum. This effect opens the possibility to extract informa- tion about both the frequency of the bispectrum as well as its shape while considering only a limited number of modes. The resonance effect is independent of the phase of the reconstructed bispectrum suggesting Fourier mode extraction could be an efficient way to detect oscillatory bispectra in the data.

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