用无菌中微子测量宇宙中的增长指数
Measuring growth index in a universe with sterile neutrinos
摘要：
广义相对论（GR）的一致性检验可以通过约束的增长指数$γ$使用红移空间失真（RSD）的测量结合其他观测。在以往的研究中，发现在2- 3 $σ$能级上$γ\approx 0.55$的GR期望值有偏差，本文重新考虑了在无中微子宇宙中对$γ$的测量。利用RSD测量结合宇宙微波背景数据（普朗克温度数据和WMAP 9年偏振数据）、重子声学振荡数据、哈勃常数直接测量、普朗克Sunyaev-Zeldovich星系团计数数据和星系切变数据，对不育中微子宇宙学模型进行了约束.我们得到了生长指标$γ=0.584^{+0.047}_{-0.048}$的约束结果，与GR期望值的一致性很好（一致性在0.6 $σ$水平上）。对于无菌中微子的参数，我们得到了$N_{\rm{eff}}=3.62^{+0.26}_{-0.42}$和$m_{ν,{\rm{sterile}}}^{\rm{eff}}=0.48^{+0.11}_{-0.14}$ eV。我们还考虑了BICEP 2数据，并使用张量模式对模型进行了分析。得到了类似的拟合结果，表明一旦宇宙中考虑了轻不育中微子，GR将与当前的观测结果很好地一致。
英文摘要：
Consistency tests for the general relativity (GR) can be performed by constraining the growth index $γ$ using the measurements of redshift-space distortions (RSD) in conjunction with other observations. In previous studies, deviations from the GR expected value of $γ\approx 0.55$ at the 2--3$σ$ level were found. In this work, we reconsider the measurement of $γ$ in a universe with sterile neutrinos. We constrain the sterile neutrino cosmological model using the RSD measurements combined with the cosmic microwave background data (Planck temperature data plus WMAP 9-yr polarization data), the baryon acoustic oscillation data, the Hubble constant direct measurement, the Planck Sunyaev-Zeldovich cluster counts data, and the galaxy shear data. We obtain the constraint result of the growth index, $γ=0.584^{+0.047}_{-0.048}$, well consistent with the GR expected value (the consistency is at the 0.6$σ$ level). For the parameters of sterile neutrino, we obtain $N_{\rm{eff}}=3.62^{+0.26}_{-0.42}$ and $m_{ν,{\rm{sterile}}}^{\rm{eff}}=0.48^{+0.11}_{-0.14}$ eV. We also consider the BICEP2 data and perform an analysis on the model with tensor modes. Similar fit results are obtained, showing that once light sterile neutrino is considered in the universe, GR will become well consistent with the current observations.
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