CAMB - LCDM with higher mass neutrinos

[Paul Anthony Fronteri]

Hey.

I have been trying to run LCDM, but with a higher mass on the neutrinos. I 3 neutrinos, where the total neutrino mass is set at 0.9 eV, 1.1 eV, 1.5 eV, 3,0 eV and 6.0eV.

However does the neutrino perturbation, delta_nu = clxnu show a huge fall in the value and then stay constant. While it works fine for 0.9 and under.

Is there an numerical approximation or something else, such that the module can't handle the higher mass?

The only change I have made is to set the mass of the neutrino to be (sum neutrino)/3.

[Antony Lewis]

Default settings do not get the neutrino transfer functions accurate at late times (because they are not directly observable anyway). There's a "neutrino_transfer" branch of the git repository that has an additional option for accurate neutrino transfer functions if you really need them.

Otherwise, yes, there are various approximations. You can play with the accuracy settings in the .ini file. However I'm not sure exactly what your problem is, you could include a plot.

[Paul Anthony Fronteri]

I switch to the setting with integrating the distribution function, massive_nu_approx = from 1 to 0.

I also changed omega_nu such that I get "the correct" value, compensating the change in mass of neutrino, since this was only fixed earlier.

The fall in delta_nu is now gone and get more sensible plots.