Hi,
I have a question related to the matter power spectra computed using CAMB. In the plot below I show the output from CAMB for the linear and non-linear P(k) (upper panel) and their ratio with the power spectra for the same cosmology but computed with the Eisenstein and Hu fitting formula without acoustic oscillations (lower panel).
In the lower panel is possible to see a small step in the power spectra close to the turn over. Why is it there? How can I compute a P(k) corrected from this?
Cheers,
Ariel
Note: when computing the non-linear power spectrum I used Min_kh_nonlinear = 0.001 instead of 0.005 in halofit.f90. Without this change the non linear P(k) shows another small step at this scale.
http://star-www.dur.ac.uk/~cmb/camb.ps
CAMB: high accuracy matter power spectrum
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Re: CAMB: high accuracy matter power spectrum
The bump in the linear spectrum (at 0.3% level) in Sept 2006 version is due to CAMB not propagating many radiation multipoles for low k values. This is good for the C_l, but does give this small error for P_k.
You can fix it by editing equations.f90 from
to
I'll include this in the next update so high_precision calculations should be accurate to ~0.1%.
You can fix it by editing equations.f90 from
Code: Select all
if (CP%Transfer%high_precision) then
EV%lmaxnr=max(nint(25*lAccuracyBoost),3)
end if
Code: Select all
if (CP%Transfer%high_precision) then
EV%lmaxnr=max(nint(25*lAccuracyBoost),3)
EV%lmaxg=max(EV%lmaxg,nint(min(8,nint(sqrt(scal) *600 * EV%q))*lAccuracyBoost))
end if