neutrino distribution

[Rui Hu]

Hi everyone,

I am confused about the neutrino distribution function in CAMB and COSMOMC. So basically, it seems we have two choices:

[math]f_\nu = g_i \frac{1}{Exp(p/T_\nu)+1} and a thermal one [math]\frac{1}{Exp(p/T_i)+1} where [math]T_i=T_\nu g_i^{1/4}

which one is actually used in CAMB and COMSOMC(it looks to me the thermal one) and why? And in COSMOMC why do we need to times [math](nnu/3)^{3/4} to get the [math]Omnuh2 but for seterile neutrino we just use [math]Omnuh2\_sterile =\frac{meffsterile}{neutrino\_mass\_fac}

BTW, especially for sterile neutrino, prof S.Pastor argued in arxiv1905.11290v3 that the first disturbution is more accurate than the thermal one. I would like to hear your comments if it uses thermal distribution in CAMB.

Looking forward to your comments!

[Antony Lewis]

The neutrino model is described in the CAMB notes. meffsterile is defined as in the Planck parameter papers.

[Rui Hu]

now I understand. Thanks a lot!