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arXiv 1306.6186astro-ph.COgr-qchep-th
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非最小耦合多场暴胀模型中的非线性曲率扰动

Non-linear curvature perturbation in multi-field inflation models with non-minimal coupling

Jonathan White, Masato Minamitsuji, Misao Sasaki

摘要:

利用δN形式,我们研究了具有非最小耦合的多场暴胀模型中的非线性曲率扰动。特别是,我们专注于δN形式主义之间的关系,适用于共形相关的约旦和爱因斯坦框架。利用爱因斯坦框架中已知的结果,我们给出了与Jordan框架曲率扰动相关的功率谱、谱倾斜和非高斯性的表达式。在绝热极限尚未达到的情况下,我们发现,在一般情况下,这些量与爱因斯坦框架曲率扰动相关的不同,也证实了它们的等价性,在没有等曲率模式。然后,我们继续考虑两个解析解的例子,第一个涉及一个非最小耦合的“旁观者”字段和第二个是一个非最小耦合的多桥膨胀模型的扩展。在第一个模型中,我们发现,预测可以很容易地与最近的普朗克结果达成一致,张量标量比一般很小,光谱倾斜可调和非高斯性抑制。在第二个模型中,我们发现,所有三个参数的预测可以大大不同于那些预测的最小耦合的情况下,和最近的普朗克结果的光谱倾斜可以用来约束非最小耦合参数。

英文摘要:

Using the δN formalism we consider the non-linear curvature perturbation in multi-field models of inflation with non-minimal coupling. In particular, we focus on the relation between the δN formalism as applied in the conformally related Jordan and Einstein frames. Exploiting results already known in the Einstein frame, we give expressions for the power spectrum, spectral tilt and non-gaussianity associated with the Jordan frame curvature perturbation. In the case that an adiabatic limit has not been reached, we find that in general these quantities differ from those associated with the Einstein frame curvature perturbation, and also confirm their equivalence in the absence of isocurvature modes. We then proceed to consider two analytically soluble examples, the first involving a non-minimally coupled `spectator' field and the second being a non-minimally coupled extension of the multi-brid inflation model. In the first model we find that predictions can easily be brought into agreement with the recent Planck results, as the tensor-to-scalar ratio is generally small, the spectral tilt tuneable and the non-gaussianity suppressed. In the second model we find that predictions for all three parameters can differ substantially from those predicted in the minimally coupled case, and that the recent Planck results for the spectral tilt can be used to constrain the non-minimal coupling parameters.

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