Non-Limber on Matter-Matter (Counts-Counts) Angular Power Spectrum

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Cristian Viglione
Posts: 1
Joined: June 10 2022
Affiliation: ICE-CSIC

Non-Limber on Matter-Matter (Counts-Counts) Angular Power Spectrum

Post by Cristian Viglione » June 10 2022

I'm using CAMBS sources to calculate matter-matter correlations in Cls and I would like to use non-Limber to perform the calculation. I'm using the python wrapper in version 1.3.5 but when I compare the results with limber_window True and False they seem to be identical (I'm using a value of 0 for limber_phi_lmin). I read in the documentation that some cases, like CMB lensing, ignore the limber_window parameter, so I was wondering if this is the case for source correlations.

Code: Select all

from camb.sources import GaussianSourceWindow, SplinedSourceWindow

lmax=4000
ls=  np.arange(2, lmax+1)

#Parameters
pars = camb.CAMBparams()
pars.set_cosmology(H0=67.74, ombh2=0.0486*0.6774**2, omch2=(0.3089-0.0486)*0.6774**2)
pars.InitPower.set_params(As=2e-9, ns=0.9667)
pars.set_for_lmax(lmax, lens_potential_accuracy=1)
pars.Want_CMB = True 
pars.NonLinear = model.NonLinear_both
pars.SourceTerms.counts_redshift = False
pars.SourceTerms.counts_velocity = False
pars.SourceWindows = [GaussianSourceWindow(redshift=0.5, source_type='counts', bias=1, sigma=0.01, dlog10Ndm=0.4)]

#Limber results
pars.SourceTerms.limber_phi_lmin = 0
pars.SourceTerms.limber_windows = True

results = camb.get_results(pars)
cls = results.get_source_cls_dict()

plt.loglog(ls, cls['W1xW1'][2:lmax+1], label='limber', c='g')
    

#Non-Limber results
pars.SourceTerms.limber_windows = False
results2 = camb.get_results(pars)
cls2 = results2.get_source_cls_dict()

plt.loglog(ls, cls2['W1xW1'][2:lmax+1], label='exact', c='r', ls='--')

plt.title('Autocorrelation Matter-Matter Cl z=0.5$', size=18)
plt.xlabel(r'$\ell$', size=18)
plt.ylabel(r'$\ell(\ell+1)C_\ell/2\pi$', size=18)
plt.xticks(fontsize = 14)
plt.yticks(fontsize = 14)
plt.legend(prop={'size': 16})
The attachment fig1.png is no longer available
I'm comparing the CAMB code to the Core Cosmology Library (CCL) since the latter does not have a non limber calculation yet and I find that CAMB produces a boost on the signal at lower l<10 in comparison to CCL when using the same conditions. So probability, this has to do with CAMB always using non limber for source correlations, could this be the case?
fig1.png
fig1.png (22.56 KiB) Viewed 104 times
Thank you!

Antony Lewis
Posts: 1787
Joined: September 23 2004
Affiliation: University of Sussex
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Re: Non-Limber on Matter-Matter (Counts-Counts) Angular Power Spectrum

Post by Antony Lewis » June 11 2022

I think it always uses non-limber for scales that are not much smaller than the window width. With limber_window=F it should not use limber on any scale.

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