A neutrino model fit to the CMB power spectrum
  The standard cosmological model, LCDM, provides an excellent fit to Cosmic
Microwave Background (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.
Shanks previously investigated a model which assumed neither exotic particles
nor a cosmological constant but instead postulated a low Hubble constant (H_0)
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 ~5eV. If we assume a low
H_0~45kms^-1Mpc^-1 then, compared to the previous purely baryonic model, we
find a significantly improved fit to the first 3 peaks of the Planck power
spectrum. Nevertheless, the goodness-of-fit is still significantly worse than
for LCDM 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 (sigma_8~0.2) 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 LCDM in
fitting ever more precise cosmological data.
