Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Science, P.O. Box 918-4, Beijing 100049, People's Republic of China.
Department of Physics, McGill University, Montréal, Québec H3A 2T8, Canada.
Phys Rev Lett. 2014 Jun 27;112(25):251301. doi: 10.1103/PhysRevLett.112.251301. Epub 2014 Jun 26.
The BICEP2 Collaboration reports a detection of primordial cosmic microwave background (CMB) B mode with a tensor-to-scalar ratio r = 0.20(-0.05)(+0.07) (68% C.L.). However, this result disagrees with the recent Planck limit r < 0.11 (95% C.L.) on constraining inflation models. In this Letter we consider an inflationary cosmology with a preceding nonsingular bounce, which gives rise to observable signatures on primordial perturbations. One interesting phenomenon is that both the primordial scalar and tensor modes can have a step feature on their power spectra, which nicely cancels the tensor excess power on the CMB temperature power spectrum. By performing a global analysis, we obtain the 68% C.L. constraints on the parameters of the model from the Planck+WP and BICEP2 data together: the jump scale log(10)(k(B)/Mpc(-1)) = -2.4 ± 0.2 and the spectrum amplitude ratio of bounce to inflation r(B) ≡ P(m)/A(s) = 0.71 ± 0.09. Our result reveals that the bounce inflation scenario can simultaneously explain the Planck and BICEP2 observations better than the standard cold dark matter model with a cosmological constant, and can be verified by future CMB polarization measurements.
BICEP2 合作组报道了原初宇宙微波背景（CMB）B 模式的探测，其张量-标量比为 r = 0.20(-0.05)(+0.07)（68%置信区间）。然而，这一结果与最近 Planck 对限制宇宙学模型的限制 r < 0.11（95%置信区间）相矛盾。在这篇快报中，我们考虑了一个具有先前非奇异反弹的宇宙学模型，这导致了原初扰动的可观测特征。一个有趣的现象是，原初标量和张量模式都可以在其功率谱上具有阶跃特征，这很好地消除了 CMB 温度功率谱上的张量过剩功率。通过进行全局分析，我们从 Planck+WP 和 BICEP2 数据一起得到了模型参数的 68%置信区间限制：跳跃尺度 log(10)(k(B)/Mpc(-1)) = -2.4 ± 0.2 和反弹到暴胀的谱幅度比 r(B)≡P(m)/A(s) = 0.71 ± 0.09。我们的结果表明，反弹暴胀情景可以比具有宇宙学常数的标准冷暗物质模型更好地同时解释 Planck 和 BICEP2 观测结果，并可以通过未来的 CMB 极化测量来验证。
