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arXiv 0907.2439hep-thastro-ph.COgr-qc
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多场DBI暴胀中的全量子三谱

On the full quantum trispectrum in multi-field DBI inflation

Shuntaro Mizuno, Frederico Arroja, Kazuya Koyama

备注：
22 pages, 10 figures, minor corrections, references are added, published version in PRD
发表信息：
Phys.Rev.D80:083517,2009
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摘要：

我们计算了多场DBI暴胀模型中由场的四点函数产生的原始曲率扰动的首阶连通四点函数。我们确认，在压缩极限和反共线极限的一致性关系举行由于在单场模型的特殊性质的DBI行动。我们还分别研究了绝热、混合和纯熵贡献的三谱的动量依赖性，发现它们具有不同的动量依赖性。这意味着，如果从熵扰动到曲率扰动的转移量非常大，则三谱可以区分多场DBI暴胀模型和单场DBI暴胀模型。大量的传递$T_{\mathcal{RS}} \gg 1 $抑制了张量标量比$r \propto T_{\mathcal{RS}}^{-2}$和双谱$f_{NL}^{equi} \propto T_{\mathcal{RS}}^{-2}$的振幅，从而可以缓解基于弦论的DBI暴胀模型的严格观测约束。另一方面，对于给定的双谱幅度，它增强了三谱$τ_{NL}^{equi} \propto T_{\mathcal{RS}}^2 f_{NL}^{equi 2}$的幅度。

英文摘要：

We compute the leading order connected four-point function of the primordial curvature perturbation coming from the four-point function of the fields in multi-field DBI inflation models. We confirm that the consistency relations in the squeezed limit and in the counter-collinear limit hold as in single field models thanks to special properties of the DBI action. We also study the momentum dependence of the trispectra coming from the adiabatic, mixed and purely entropic contributions separately and we find that they have different momentum dependence. This means that if the amount of the transfer from the entropy perturbations to the curvature perturbation is significantly large, the trispectrum can distinguish multi-field DBI inflation models from single field DBI inflation models. A large amount of transfer $T_{\mathcal{RS}} \gg 1 $ suppresses the tensor to scalar ratio $r \propto T_{\mathcal{RS}}^{-2}$ and the amplitude of the bispectrum $f_{NL}^{equi} \propto T_{\mathcal{RS}}^{-2}$ and so it can ease the severe observational constraints on the DBI inflation model based on string theory. On the other hand, it enhances the amplitude of the trispectrum $τ_{NL}^{equi} \propto T_{\mathcal{RS}}^2 f_{NL}^{equi 2}$ for a given amplitude of the bispectrum.

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