http://arxiv.org/abs/1402.5502
The current standard cosmological model, LCDM, provides an excellent fit to the WMAP and Planck CMB data. However, the model has well known problems. For example, the cosmological constant is fine tuned to 1 part in 10^100 and the cold dark matter (CDM) particle is not yet detected in the laboratory. Here we seek an alternative model to LCDM which makes minimal assumptions about new physics. This is based on previous work by Shanks who investigated a model which assumed neither exotic particles nor a cosmological constant but instead postulated a low Hubble constant (H_0) to help allow a baryon density which was compatible with an inflationary model with zero spatial curvature. However, the recent Planck results make it more difficult to reconcile such a model with the cosmic microwave background (CMB) temperature fluctuations. Here we relax the previous assumptions to assess the effects of assuming standard model neutrinos of moderate mass (~5eV) but with no CDM and no cosmological constant. If we assume a low H_0~45kms^-1Mpc^-1 then we now find a reasonable fit to the Planck CMB power spectrum. This model is related to the 11eV sterile neutrino model of Angus (2009) except there a cosmological constant was assumed with H_0~70kms^-1Mpc^-1. The problem for both these models is that the amplitude of fluctuations is low (sigma_8~0.2) making it difficult to form galaxies by the present day. Angus advocated a modified gravity model to increase the growth rate of perturbations. Another approach is to invoke seeds for galaxy formation that might have existed just after decoupling. One possibility is cosmic string wakes but we believe seeds from a primordial magnetic field are more in the spirit of our `what you see is what you get’ model.
T. Shanks, R. Johnson, J. Schewtschenko, et. al.
Tue, 25 Feb 14
23/59