### CDM power spectrum from pyCAMB

Posted:

**March 01 2018**I was running a quick consistency check between power spectra generated in pyCAMB and the command line executable and I'm a bit confused about some of the output. I've created an interpolation object:

where 'pars' has the same cosmology as the params.ini used in the executable. The ratio of the two is plot here, which gives exactly what you'd expect:

I then tried to do the same with the CDM power spectrum, by setting changing
in the params.ini file, and setting

in the python program. When I compare these two power spectra however, I get:

so the power spectra are no longer the same. Am I right in expecting them to be the same, or am I attempting to get the CDM power spectrum the wrong way? Do var1 and var2 not select which fluids we want power spectra for?

Code: Select all

`PK=camb.get_matter_power_interpolator(pars,zmin=98,zmax=100,nz_step=100,nonlinear=False,var1="delta_tot")`

I then tried to do the same with the CDM power spectrum, by setting changing

Code: Select all

`transfer_power_var=2`

Code: Select all

`PK=camb.get_matter_power_interpolator(pars,zmin=98,zmax=100,nz_step=100,nonlinear=False,var1="delta_CDM")`

so the power spectra are no longer the same. Am I right in expecting them to be the same, or am I attempting to get the CDM power spectrum the wrong way? Do var1 and var2 not select which fluids we want power spectra for?