Dear All,
I have a question about neutrino parameters in parameter file for camb.
(Recently, I downloaded the most recent version of camb.)
I thought that, if omnuh2=0.0, then no matter which numbers I use for the following parameter:
nu_mass_eigenstates
massive_neutrinos
nu_mass_fractions
nu_mass_degeneracies,
there is no change in P(k) matter power spectrum, because there is nothing to be distributed for each massive neutrino.
But, when I changed the values for these parameters like this:
nu_mass_eigenstates = 1 -> 0
massive_neutrinos = 1. -> 0.
nu_mass_fractions = 1. -> 0.
nu_mass_degeneracies = 1. -> 0.
with fixing omnuh2=0.0 and massless_neutrino = 0.0,
I found somehow big difference, where the first trial gives more suppression on small scales.
(During this comparison, share_delta_neff = T and F gave the same result.)
Just in case, here is my parameter file.
/cosmo_files.php?file=Minji_Oh/ ... shareT.ini
I checked several questions on neutrinos parameters in this forum and saw the comments. From the comments and within my understanding, I think massive_neutrino is not affected by massless_neutrino.
One thing among the comments which is not clear for me was "Massless neutrinos are always calculated". This may be the reason I cannot solve the above problem, but I'm not sure.
Can anybody give me some comments about this?
Which one is the right result among the above results?
Thanks in advance,
Minji Oh
[CAMB] parameters for neutrinos
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Re: [CAMB] parameters for neutrinos
You need to keep the total number of massive and massless neutrinos the same, otherwise you are changing N_eff. Setting the mass to zero just makes the massive neutrinos have zero mass, it doesn't remove them.
[CAMB] parameters for neutrinos
Dear Antony Lewis,
Thank you for your reply~!
Sincerely,
Minji
Thank you for your reply~!
Sincerely,
Minji