CAMB: massive neutrinos & neutrino temperature

[Jascha Schewtschenko]

Hi everyone,

I have just a question about the new CAMB code (march 2013+) and how to set up massive neutrinos and their temperature properly. According to the readme, the degeneracy parameter determines the temperature, so is it correct to assume that the following configuration

massive_neutrinos=2
massless_neutrinos=1
nu_mass_degeneracies=4
omnuh2=0.006450616

simulates 2 massive neutrinos and 1 massless neutrinos with Neff=5 and a neutrino temperature for the massive neutrino of [tex]2^{0.25} T_{\nu,SM}[/tex] and [tex]T_{\nu,SM}[/tex] for the massless one (both times assuming inst. decoupling of course) and with a 2 times degenerate neutrino mass eigenstate for the massive ones of [tex]m_\nu[/tex] ~ (omnuh2*93.1/2)/(2^0.75) ?

Additional question regarding very massive neutrinos (I know it was already answered by antony once almost half a decade ago, but CAMB has been improved since then): Is it possible to use the degeneracy parameter to do the linear calculations very massive neutrinos (up to kev scale) and therefore certain WDM models?

Thanks in advance for helpful answers/clarifications.

[Antony Lewis]

The September 2013 version changes the neutrino input parameters slightly, so it is hopefully now slightly less confusing. The new parameterization is documented with some examples in the notes at

http://cosmologist.info/notes/CAMB.pdf