标题： α吸引子模型中$α$参数的新型CMB约束 显示英文标题

标题： Novel CMB constraints on the $α$ parameter in alpha-attractor models

摘要： 宇宙学$\alpha$吸引子是一类有吸引力的暴胀模型。 它们对大尺度观测量给出了普遍的预测，这些预测广泛地独立于标量场势的函数形式。 在本工作中，我们推导了改进的解析预测，这些预测明确地表现出与再加热持续时间和参数$\alpha$的依赖关系。 我们在贝叶斯研究框架下将这些预测与普朗克和BICEP/Keck 2018数据进行比较，对$\alpha$使用均匀的对数和线性先验。 我们改进的普遍预测允许直接对再加热持续时间进行约束。 此外，虽然众所周知CMB对张量-标量比的约束可用于对$\alpha$参数施加上限，但我们证明包括标量谱倾斜的$\alpha$依赖性可以对$\alpha$产生新的约束。 特别是，对于小的$\alpha$，标量光谱倾斜与$\log_{10}\alpha$成比例，而与势能形状无关。 对于减小的$\alpha$，这最终会使模型与CMB测量结果产生矛盾，从而从下限限制$\alpha$的大小。 因此，除了张量-标量比的上界外，我们还推导了$\alpha$在$\alpha$-attractor T模型中的第一个下界，$\log_{10}{\alpha} = -4.2^{+5.4}_{-8.6}$在$95\%$C.L.。 显示英文摘要

摘要： Cosmological $\alpha$-attractors are a compelling class of inflationary models. They lead to universal predictions for large-scale observables, broadly independent from the functional form of the inflaton potential. In this work we derive improved analytical predictions for the large-scale observables, whose dependence on the duration of reheating and the parameter $\alpha$ is made explicit. We compare these with Planck and BICEP/Keck 2018 data in the framework of a Bayesian study, employing uniform logarithmic and linear priors for $\alpha$. Our improved universal predictions allow direct constraints on the duration of reheating. Furthermore, while it is well-known that CMB constraints on the tensor-to-scalar ratio can be used to place an upper bound on the $\alpha$ parameter, we demonstrate that including the $\alpha$-dependence of the scalar spectral tilt yields novel constraints on $\alpha$. In particular, for small $\alpha$, the scalar spectral tilt scales with $\log_{10}\alpha$, regardless of the specific potential shape. For decreasing $\alpha$, this eventually puts the models in tension with CMB measurements, bounding the magnitude of $\alpha$ from below. Therefore, in addition to the upper bound from the tensor-to-scalar ratio, we derive the first lower bound on the magnitude of $\alpha$ for $\alpha$-attractor T-models, $\log_{10}{\alpha} = -4.2^{+5.4}_{-8.6}$ at $95\%$ C.L. .