标题： 多场 inflation 的有效场论 à la Weinberg 显示英文标题

标题： Effective Field Theory of Multi-Field Inflation a la Weinberg

摘要： 我们采用多场膨胀的有效场论方法，这是Weinberg工作的推广。 在此方法中，除了标准拉格朗日项之外，还考虑了修正项的第一阶项。 这些项包含场（包括标量场和度规）的最多四阶导数。 结果显示，在一般形式下，最终导致非高斯性的相互作用项可能的形状。 此外，一般来说，声速不同但接近于1。 由于此方法最初并未区分绝热模，所以我们为特定的两场模型定义了绝热模和熵模。 研究表明，绝热模和熵模的非高斯性在形状和幅度上是相关的。 结果表明，即使速度接近于1，多场情况下也可能存在大的非高斯性。 非高斯性的大小取决于相空间中经典路径在哈勃单位下的曲率，曲率越大，非高斯性越大。 此外，强调了绝热和熵扰动的时间导数由于平移对称性不会变换，而原始扰动也不会。 尽管其中两种特定组合在这种对称性下是不变的，应使用这些组合来构建多场膨胀的有效场理论。 显示英文摘要

摘要： We employ the effective field theory approach for multi-field inflation which is a generalization of Weinberg's work. In this method the first correction terms in addition to standard terms in the Lagrangian have been considered. These terms contain up to the fourth derivative of the fields including the scalar field and the metric. The results show the possible shapes of the interaction terms resulting eventually in non-Gaussianity in a general formalism. In addition generally the speed of sound is different but almost unity. Since in this method the adiabatic mode is not discriminated initially so we define the adiabatic as well as entropy modes for a specific two-field model. It has been shown that the non-Gaussianity of the adiabatic mode and the entropy mode are correlated in shape and amplitude. It is shown that even for speed close to unity large non-Gaussianities are possible in multi-field case. The amount of the non-Gaussianity depends on the curvature of the classical path in the phase-space in the Hubble unit such that it is large for the large curvature. In addition it is emphasized that the time derivative of adiabatic and entropy perturbations do not transform due to the shift symmetry as well as the original perturbations. Though two specific combinations of them are invariant under such a symmetry and these combinations should be employed to construct an effective field theory of multi-field inflation.