The inflationary origin of primordial black holes (PBHs) relies on a large enhancement of the power spectrum ${\Delta }_{\zeta }$ of the curvature fluctuation $\zeta$ at wavelengths much shorter than those of the cosmic microwave background anisotropies. This is typically achieved in models where $\zeta$ evolves without interacting significantly with additional (isocurvature) scalar degrees of freedom. However, quantum gravity inspired models are characterized by moduli spaces with highly curved geometries and a large number of scalar fields that could vigorously interact with $\zeta$ (as in the cosmological collider picture). Here we show that isocurvature fluctuations can mix with $\zeta$ inducing large enhancements of its amplitude. This occurs whenever the inflationary trajectory experiences rapid turns in the field space of the model leading to amplifications that are exponentially sensitive to the total angle swept by the turn, which induce characteristic observable signatures on ${\Delta }_{\zeta }$. We derive accurate analytical predictions and show that the large enhancements required for PBHs demand noncanonical kinetic terms in the action of the multifield system.

中文翻译：

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在多场通货膨胀中播种原始黑洞

原始黑洞（PBH）的膨胀起因取决于功率谱的大幅提高 ${\Delta }_{\zeta }$ 曲率波动的 $\zeta$波长远小于宇宙微波背景各向异性的波长。这通常是在其中$\zeta$在不与其他（等曲率）标量自由度显着交互的情况下进行演化。但是，受量子引力启发的模型的特征是具有高度弯曲的几何形状的模空间和大量可以与之强烈相互作用的标量场。$\zeta$（如宇宙对撞机图片所示）。在这里，我们表明等曲率波动可以与$\zeta$导致其幅度大大增强。每当膨胀轨迹在模型的场空间中经历快速转向，导致放大倍数对转向所扫过的总角度呈指数敏感时，就会发生这种情况，从而在镜头上引起特征性的可观察特征${\Delta }_{\zeta }$。我们得出准确的分析预测结果，并表明在多场系统的作用中，PBHs所需的大量增强要求非规范动力学项。