多场暴胀中全新的精确双谱形状
New exact bispectrum shapes in multifield inflation
AI总结：
该研究利用多重暴胀涨落的有效场论，对原初双谱进行解析计算，非微扰处理曲率和等曲率涨落二次混合。通过推导积分表示、证明双谱简化及考虑特定相互作用展示方法威力，得到挤压极限等结果，为多场原初非高斯性打开新解析窗口。
AI中文摘要：
利用多重暴胀涨落的有效场论，我们首次对原初双谱进行了解析计算，其中曲率和等曲率涨落之间的二次混合被非微扰地处理。基于文献[Huenupi:2026abj]中提出的精确线性解的算符表示，我们为这些混合模式函数推导了一个更简单的积分表示。我们证明所有尺度不变的树级双谱都简化为一个单顶点图，可通过对独立的预计算边核进行施温格参数积分来评估。通过考虑三次时间导数相互作用$\dot{\pic}^3$展示了我们方法的威力，在小混合时导致纯单场等边现象学。相反，在强混合时，得到的双谱形状与等边模板去相关，成为真正的多场，具有大振幅，这激发了专门的数据分析。对于裸质量为$m$的等曲率场，在任何无量纲混合强度$\la$下，解析地以封闭形式获得了挤压极限，其具有由$\nu_{\rm eff} = i \muf=\sqrt{9/4-m^2/H^2-\la^2}$设定的宇宙学对撞机信号，有效质量由$\la$修饰，如先前在数值或半解析计算中所证明的。我们的结果涵盖了通常微扰计算的$\la \ll 1$极限，其中信号幅度必然小，但也超越了它们，从而为大的多场原初非高斯性打开了一个新的解析窗口。
英文摘要：
Using the effective field theory of multiple inflationary fluctuations, we present the first analytical calculation of the primordial bispectrum in which the quadratic mixing between curvature and isocurvature fluctuations is treated non-perturbatively. Building upon the operator representation of the exact linear solutions proposed in Ref.~\cite{Huenupi:2026abj}, we derive a simpler integral representation for these mixed mode functions. We prove that all scale-invariant tree-level bispectra reduce to a single vertex diagram, which can be evaluated with a Schwinger-parameter integral over independent pre-computable leg kernels. We showcase the power of our approach by considering the cubic time-derivative interaction $\dot{\pic}^3$, which leads to a purely single-field, equilateral phenomenology at small mixing. On the contrary, at strong mixing the obtained bispectrum shapes decorrelate from the equilateral template and become genuinely multifield, with a large amplitude, motivating a dedicated data analysis. The squeezed limit is obtained analytically in a closed form at any dimensionless mixing strength $\la$ for an isocurvature field of bare mass $m$ and features a cosmological collider signal set by $ν_{\rm eff} = i \muf=\sqrt{9/4-m^2/H^2-\la^2}$, with an effective mass dressed by $\la$, as previously evidenced in numerical or semi-analytical calculations. Our results encompass the $\la \ll 1$ limit of usual perturbative calculations, where the amplitude of the signal is necessarily small, but they also surpass them, thus opening a new analytical window into large multifield primordial non-Gaussianities.
