标题： 宇宙扰动的规范不变作用量的唯一性 显示英文标题

标题： Uniqueness of the gauge invariant action for cosmological perturbations

摘要： 在二阶微扰理论中，单场暴胀模型中规范不变微扰的不同定义是已知的。 因此相应的规范不变三次作用量并不具有相同的形式。 在这里我们表明，规范不变变量的一种选择的三次作用量具有如下意义上的唯一性：对于任何其他非线性相关的变量，其作用量可以转化为相同的体作用量，加上额外的边界项。 这些边界项对应于超曲面的选择，并会生成bispectrum的额外不相连贡献。 我们还讨论了作用量在共形框架下的唯一性。 当用均匀场超曲面上的规范不变曲率微扰来表示时，宇宙微扰的作用量具有唯一的形式，与原始爱因斯坦框架或乔丹框架无关。 关键在于规范不变的共动曲率微扰是框架无关的，这在证明两个框架的量子等价性方面非常有用，因此在计算非最小耦合理论（如希格斯暴胀）中的量子效应时非常有帮助。 显示英文摘要

摘要： In second order perturbation theory different definitions are known of gauge invariant perturbations in single field inflationary models. Consequently the corresponding gauge invariant cubic actions do not have the same form. Here we show that the cubic action for one choice of gauge invariant variables is unique in the following sense: the action for any other, non-linearly related variable can be brought to the same bulk action, plus additional boundary terms. These boundary terms correspond to the choice of hypersurface and generate extra, disconnected contributions to the bispectrum. We also discuss uniqueness of the action with respect to conformal frames. When expressed in terms of the gauge invariant curvature perturbation on uniform field hypersurfaces the action for cosmological perturbations has a unique form, independent of the original Einstein or Jordan frame. Crucial is that the gauge invariant comoving curvature perturbation is frame independent, which makes it extremely helpful in showing the quantum equivalence of the two frames, and therefore in calculating quantum effects in nonminimally coupled theories such as Higss inflation.