Tension between the power spectrum of density perturbations measured on large and small scales
Abstract
There is a tension between measurements of the amplitude of the power spectrum of density perturbations inferred using the cosmic microwave background (CMB) and directly measured by largescale structure (LSS) on smaller scales. We show that this tension exists, and is robust, for a range of LSS indicators including clusters, lensing and redshift space distortions and using CMB data from either Planck or WMAP +SPT /ACT . One obvious way to try to reconcile this is the inclusion of a massive neutrino which could be either active or sterile. Using Planck and a combination of all the LSS data we find that (i) for an active neutrino ∑m_{ν}=(0.357 ±0.099 ) eV and (ii) for a sterile neutrino m_{sterile}^{eff}=(0.67 ±0.18 ) eV and ∆ N_{eff}=0.32 ±0.20 . This is, however, at the expense of a degraded fit to Planck temperature data, and we quantify the residual tension at 2.5 σ and 1.6 σ for massive and sterile neutrinos, respectively. We also consider alternative explanations including a lower redshift for reionization that would be in conflict with polarization measurements made by WMAP and ad hoc modifications to the primordial power spectrum.
 Publication:

Physical Review D
 Pub Date:
 May 2015
 DOI:
 10.1103/PhysRevD.91.103508
 arXiv:
 arXiv:1409.2769
 Bibcode:
 2015PhRvD..91j3508B
 Keywords:

 98.80.k;
 98.65.Dx;
 98.80.Es;
 Cosmology;
 Superclusters;
 largescale structure of the Universe;
 Observational cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 18 pages, 11 figures