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CAMB: Two points correlation function result is small

Posted: July 30 2022
by Cliff Schwartz
I want to use CAMB to calculate [math]
where [math] is CMB temperature anisotropies over angular. (Just TT)

This can be done by CAMB module correlations

Code: Select all

from camb import correlations
pars.set_cosmology(H0=67.5, ombh2=0.022, omch2=0.122, mnu=0.06, omk=0, tau=0.06)
pars.InitPower.set_params(As=2.1e-9, ns=0.9682, r=0)
pars.set_for_lmax(4000, lens_potential_accuracy=1);
results = camb.get_results(pars)
lensed_cl = results.get_lensed_scalar_cls()
corrs, xvals, weights = correlations.gauss_legendre_correlation(lensed_cl)
Then I plotted the figure between [math] and [math]. (TT~[math])

Unfortunately, I found that the result is too small. The peak is smaller than the standard model when [math] is 75 degree. Besides, I calculated the [math] and the result is 600 approximately, lower than the standard value 42496.5 .

I am wondering to know the result given by CAMB is so small?

Thank you very much.