标题： 用CMB张量各向异性约束引力作用 显示英文标题

标题： Constraining the gravitational action with CMB tensor anisotropies

摘要： 我们对在PPF-CAMB框架内一类f(R)引力理论中张量各向异性对宇宙微波背景的印记进行了完整分析。 我们推导了获得标准温度和极化功率谱所需的宇宙学背景和引力波扰动方程，仔细包括来自f(R)对背景和扰动方程修改的所有效应。 对于R^n引力，我们表明当n不等于2时，辐射主导时期的初始条件与广义相对论中找到的相同。 我们还发现，通过进行涉及修改背景演化而保持扰动方程固定或固定背景为Lambda-CDM模型并修改扰动方程的模拟，温度和极化谱中偏离广义相对论的主要贡献可以归因于背景的修改。 这证明了在f(R)引力的扰动研究中使用正确背景的重要性。 最后观察到B模式功率谱有所增强，这可能允许较低的暴胀能量尺度。 显示英文摘要

摘要： We present a complete analysis of the imprint of tensor anisotropies on the Cosmic Microwave Background for a class of f(R) gravity theories within the PPF-CAMB framework. We derive the equations, both for the cosmological background and gravitational wave perturbations, required to obtain the standard temperature and polarization power spectra, taking care to include all effects which arise from f(R) modifications of both the background and the perturbation equations. For R^n gravity, we show that for n different from 2, the initial conditions in the radiation dominated era are the same as those found in General Relativity. We also find that by doing simulations which involve either modifying the background evolution while keeping the perturbation equations fixed or fixing the background to be the Lambda-CDM model and modifying the perturbation equations, the dominant contribution to deviations from General Relativity in the temperature and polarization spectra can be attributed to modifications in the background. This demonstrates the importance of using the correct background in perturbative studies of f(R) gravity. Finally an enhancement in the B-modes power spectra is observed which may allow for lower inflationary energy scales.