Tilt of primordial gravitational wave spectrum in a universe with sterile neutrinos  

作　　者：Li YunHe ZHANG JingFei ZHANG Xin 

机构地区：[1]Department of Physics, College of Sciences, Northeastern University [2]Center for High Energy Physics, Peking University

出　　处：《Science China(Physics,Mechanics & Astronomy)》2014年第8期1455-1459,共5页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 11175042);the National Ministry of Education of China (Grant No. N120505003)

摘　　要：In this work, we constrain the spectral index nt of the primordial gravitational wave power spectrum in a universe with sterile neutrinos by using the Planck temperature data, the WMAP 9-year polarization data, the baryon acoustic oscillation data, and the BICEP2 data. We call this model the ACDM＋r＋vs＋nt model. The additional massive sterile neutrino species can significantly relieve the tension between the Planck and BICEP2 data, and thus can reduce the possible effects of this tension on the fit results of nt. To constrain the parameters of sterile neutrino, we also utilize the Hubble constant direct measurement data, the Planck Sunyaev-Zeldovich cluster counts data, the Planck CMB lensing data, and the cosmic shear data. We find that due to the fact that the BICEP2 data are most sensitive to the multipole （ - 150 corresponding to k - 0.01 Mpc^-1, there exists a strong anticorrelation between nt and r0.0o2 in the BICEP2 data, and this further results in a strongly blue-tilt spectrum. However, a slightly red-tilt tensor power spectrum is also allowed by the BICEP2 data in the region with larger value of r0.00z. By using the full data sets, we obtain mvisterile ^eff = 0.48 -0.13^＋0.11 eV, Near = 3.73 -0.37^＋0.34, and nt = 0.96 -0.63^ ＋0.48 for the ACDM＋r＋vs＋nt model.In this work,we constrain the spectral index ntof the primordial gravitational wave power spectrum in a universe with sterile neutrinos by using the Planck temperature data,the WMAP 9-year polarization data,the baryon acoustic oscillation data,and the BICEP2 data.We call this model theΛCDM+r+νs+ntmodel.The additional massive sterile neutrino species can significantly relieve the tension between the Planck and BICEP2 data,and thus can reduce the possible effects of this tension on the fit results of nt.To constrain the parameters of sterile neutrino,we also utilize the Hubble constant direct measurement data,the Planck Sunyaev-Zeldovich cluster counts data,the Planck CMB lensing data,and the cosmic shear data.We find that due to the fact that the BICEP2 data are most sensitive to the multipole～150 corresponding to k～0.01 Mpc-1,there exists a strong anticorrelation between ntand r0.002in the BICEP2 data,and this further results in a strongly blue-tilt spectrum.However,a slightly red-tilt tensor power spectrum is also allowed by the BICEP2 data in the region with larger value of r0.002.By using the full data sets,we obtain meffν,sterile=0.48+0.11-0.13eV,Neff=3.73+0.34-0.37,and nt=0.96+0.48-0.63for theΛCDM+r+νs+ntmodel.

关 键 词：primordial gravitational waves BICEP2 sterile neutrino tilt of tensor power spectrum 

分 类 号：O572.321[理学—粒子物理与原子核物理]