The natural inflation model with a periodic cosine potential is ruled out by recent Planck 2018 data for the decay constant f ≲ 5.5 MPl. If the Planck data is combined with the BICEP Keck array and BAO data, the model is excluded (at 2-σ) for all values of f. In this context, we revisit the model when the pseudoscalar inflation ϕ is coupled with a gauge field via a coupling of the form α/fϕFF̃, where F(F̃) denotes the gauge field (dual) strength tensor, and α is the coupling constant. The back-reactions associated with the gauge field production during the later stages of inflation extend the duration of inflation. We numerically evaluate the dynamics of the fields while neglecting the effects due to the perturbations in the inflaton field. It allows us to determine the scalar and tensor power spectra leading to the calculations of observables at the Cosmic Microwave Background (CMB) scales. We find that the natural inflation model survives the test of the latest data only for a certain range of the coupling constant α. Our analysis shows that the latest constraints coming from the scalar spectral index are more stringent than the ones arising from the non-gaussianities and the running of the scalar spectrum. This leads to lower and upper bounds on ξ*, the parameter that controls the growth of the gauge field.

中文翻译：

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CMB 对仪表场生产自然膨胀的限制


最近的普朗克 2018 年数据排除了具有周期性余弦电位的自然膨胀模型，其衰减常数 f ≲ 5.5 MPl。如果普朗克数据与 BICEP Keck 数组和 BAO 数据相结合，则对于 f 的所有值，模型都将被排除（在 2-σ 处）。在这种情况下，当伪标量膨胀φ通过 α/fφFF̃ 形式的耦合与规范场耦合时，我们重新审视了该模型，其中 F（F̃） 表示规范场（对偶）强度张量，α 是耦合常数。在通货膨胀的后期阶段，与仪表场生产相关的反作用力延长了通货膨胀的持续时间。我们以数值方式评估了场的动力学，同时忽略了膨胀场中扰动的影响。它使我们能够确定标量和张量功率谱，从而在宇宙微波背景 （CMB） 尺度上计算可观测物。我们发现，自然膨胀模型仅在耦合常数α的一定范围内经受住了最新数据的检验。我们的分析表明，来自标量光谱指数的最新约束比来自非高斯性和标量光谱运行的约束更严格。这导致了 ξ* 的下限和上限，ξ* 是控制规范字段增长的参数。