## hidden sector dark matter

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
Abir Sarkar
Posts: 16
Joined: July 07 2014
Affiliation: Raman Research Institute

### hidden sector dark matter

Hi Antony,

we are working with some dark matter models where the dark matter may be a sterile neutrino which is coupled through some secret interaction with a hidden sector, which has a different temperature.

In this case, the distribution function of the sterile neutrino will have a different temperature.

In order to do that , do I have to modify the distribution function of the massive neutrino, or it is internally taken care of when you provide

"share_delta_neff =F" and provide the mass eigenstate and degeneracies in the params.ini?

Abir

Antony Lewis
Posts: 1659
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

### Re: hidden sector dark matter

It can handle neutrinos with different temperatures via the degeneracies (but assumes they are Fermi-Dirac distributions).

Abir Sarkar
Posts: 16
Joined: July 07 2014
Affiliation: Raman Research Institute

### hidden sector dark matter

Hi,

But, if we do not change the distribution function itself, which is FD but with a different temperature, how can the changes in pressure and anisotropic stress are taken into account?

As fas as I understood the code, it uses the degeneracies to calculate some effective "nu_masses" and use it to get the appropriate $\epsilon$ = $\sqrt{q^2+m^2a^2}$. But the dynamics of this dark matter is not taken care of, unless the distribution function is written with different temperature.

It will be really helpful if you kindly clear this confusion.

Regards,

Abir

Antony Lewis
Posts: 1659
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

### Re: hidden sector dark matter

Things only depends on m/T as long as the distribution is Fermi-Dirac. See the CAMB notes for more discussion.

Abir Sarkar
Posts: 16
Joined: July 07 2014
Affiliation: Raman Research Institute

### hidden sector dark matter

Hi Antony,

Thanks a lot for your reply. The dynamics of the code is clear now.

Does the same apply for CMBFAST too?

Abir