论文标题
多场通货膨胀中有效音速的独立模型方法
Model-independent approach to effective sound speed in multi-field inflation
论文作者
论文摘要
对于满足爱因斯坦方程式的任何物理系统，共同的曲率扰动满足涉及动量依赖有效声速的方程式，对任何具有明确定义的能量压力张量的系统有效，包括多场通胀模型。我们得出了一个通用的独立于模型的公式，用于对绝热扰动的有效声速，对通用的场空间度量有效，而无需假设任何近似近似以整合熵扰动，但表达了动量依赖于总能量压力压力张者组成部分的动量有效音速。作为应用程序，我们研究了许多磁场之间具有动力学耦合的两场模型，确定了有效理论的单个曲率模式，并表明动量依赖性有效的声速充分说明了曲率扰动功率谱的预测。我们的结果表明，依赖动量的有效音速是一个方便的方案，用于描述所有接受单场有效理论的通货膨胀模型，包括多场系统中存在的熵扰动的影响。
For any physical system satisfying the Einstein's equations, the comoving curvature perturbations satisfy an equation involving the momentum-dependent effective sound speed, valid for any system with a well defined energy-stress tensor, including multi-fields models of inflation. We derive a general model-independent formula for the effective sound speed of comoving adiabatic perturbations, valid for a generic field-space metric, without assuming any approximation to integrate out entropy perturbations, but expressing the momentum-dependent effective sound speed in terms of the components of the total energy-stress tensor. As an application, we study a number of two-field models with a kinetic coupling between the fields, identifying the single curvature mode of the effective theory and showing that momentum-dependent effective sound speed fully accounts for the predictions for the power spectrum of curvature perturbations. Our results show that the momentum-dependent effective sound speed is a convenient scheme for describing all inflationary models that admit a single-field effective theory, including the effects of entropy perturbations present in multi-fields systems.
