A neutrino model fit to the CMB power spectrum

Shanks, T.; Johnson, R.W.F.; Schewtschenko, J.A.; Whitbourn, J.R.

Abstract

The standard cosmological model, Λ cold dark matter (ΛCDM), provides an excellent fit to cosmic microwave background (CMB) data. However, the model has well-known problems. For example, the cosmological constant, Λ, is fine-tuned to 1 part in 10100 and the CDM particle is not yet detected in the laboratory. Shanks previously investigated a model which assumed neither exotic particles nor a cosmological constant but instead postulated a low Hubble constant (H0) to allow a baryon density compatible with inflation and zero spatial curvature. However, recent Planck results make it more difficult to reconcile such a model with CMB power spectra. Here, we relax the previous assumptions to assess the effects of assuming three active neutrinos of mass ≈5 eV. If we assume a low H0 ≈ 45 km s−1 Mpc−1 then, compared to the previous purely baryonic model, we find a significantly improved fit to the first three peaks of the Planck power spectrum. Nevertheless, the goodness of fit is still significantly worse than for ΛCDM and would require appeal to unknown systematic effects for the fit ever to be considered acceptable. A further serious problem is that the amplitude of fluctuations is low (σ8 ≈ 0.2), making it difficult to form galaxies by the present day. This might then require seeds, perhaps from a primordial magnetic field, to be invoked for galaxy formation. These and other problems demonstrate the difficulties faced by models other than ΛCDM in fitting ever more precise cosmological data.

Citation

Shanks, T., Johnson, R., Schewtschenko, J., & Whitbourn, J. (2014). A neutrino model fit to the CMB power spectrum. Monthly Notices of the Royal Astronomical Society, 445(3), 2836-2841. https://doi.org/10.1093/mnras/stu1956

• Journal Article Type: Article
• Acceptance Date: Sep 18, 2014
• Publication Date: Dec 1, 2014
• Deposit Date: Jun 2, 2014
• Publicly Available Date: May 21, 2015
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 445
• Issue: 3
• Pages: 2836-2841
• DOI: https://doi.org/10.1093/mnras/stu1956
• Keywords: Cosmology: observations, Large-scale structure of Universe.
• Public URL: https://durham-repository.worktribe.com/output/1451923
• Related Public URLs: http://ukads.nottingham.ac.uk/abs/2014arXiv1402.5502S