Constraints on primordial gravitational waves with variable sound speed from current CMB data
Constraints on primordial gravitational waves with variable sound speed from current CMB data
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当前 CMB 数据对变声速原初引力波的约束
DOI：
10.1103/physrevd.86.123512
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发表时间：
2012-07
期刊：
影响因子：
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通讯作者：
Yin-Zhe Ma
中科院分区：
文献类型：
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作者：
Cheng Cheng;Qing-Guo Huang;Xiao-Dong Li;Yin-Zhe Ma
我们对通货膨胀一致性关系的观测效果进行了全面的考察。我们关注具有一致性关系r = -8c(s)n(t)的一般单场暴胀模型，利用七年WMAP数据、宇宙河外偏振张量功率谱数据背景成像以及五年WMAP观测数据对非高斯参数f(NL)(equil)和f(NL)(orth)的约束研究声速c(s)的观测约束。我们发现，如果 c(s) 很小，则对张量与标量比 r 的约束会更严格，因为大倾斜 n(t) 受到观测结果的强烈约束。对于 c(s) = 1、0.1 和 0.01 模型，我们在 95.4% 置信水平 (CL) 下获得 r < 0.37、0.27 和 0.09 (dn(s)/d lnk = 0)。当c(s)取较小值时，r和n(s)之间的正相关性也会导致对n(s)上限的约束稍微严格，而标量谱指数dn(s)/d lnk的运行一般不受影响。对于声速c(s)，仅使用宇宙微波背景功率谱数据并不能很好地约束，而考虑f(NL)(equil)和f(NL)(orth)先验即可得到约束。通过f(NL)(equil)和f(NL)(orth)的约束数据，我们发现，在99.7% CL时，c(s)小于或相似于0.01的区域被排除在外，而c(s) = 1的情况（单场慢滚膨胀）在68.3% CL时稍微不利。此外，将f(NL)(等)和f(NL)(orth.)纳入分析中可以改善对r和n(s)的约束。我们进一步讨论我们的约束对通胀模型测试的影响。 DOI：10.1103/PhysRevD.86.123512
We make a comprehensive investigation of the observational effect of the inflation consistency relation. We focus on the general single-field inflation model with the consistency relation r = -8c(s)n(t), and investigate the observational constraints of sound speed c(s) by using the seven-year WMAP data, the background imaging of cosmic extragalactic polarization tensor power spectrum data, and the constraints on non-Gaussian parameters f(NL)(equil) and f(NL)(orth) from the five-year WMAP observations. We find that the constraints on the tensor-to-scalar ratio r is much tighter if c(s) is small, since a large tilt n(t) is strongly constrained by the observations. We obtain r < 0.37, 0.27, and 0.09 (dn(s)/d lnk = 0) for c(s) = 1, 0.1, and 0.01 models at 95.4% confidence level (CL). When taking smaller values of c(s), the positive correlation between r and n(s) also leads to a slightly tighter constraint on the upper bound of n(s), while the running of scalar spectral index dn(s)/d lnk is generally unaffected. For the sound speed c(s), it is not well constrained if only the cosmic microwave background power spectrum data is used, while the constraints are obtainable by taking f(NL)(equil) and f(NL)(orth) priors into account. With the constraining data of f(NL)(equil) and f(NL)(orth), we find that, c(s) less than or similar to 0.01 region is excluded at 99.7% CL, and the c(s) = 1 case (the single-field slow-roll inflation) is slightly disfavored at 68.3% CL. In addition, the inclusion of f(NL)(equil.) and f(NL)(orth.) into the analysis can improve the constraints on r and n(s). We further discuss the implications of our constraints on the test of inflation models. DOI: 10.1103/PhysRevD.86.123512