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 clxg for lcdm
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Omar Ruiz Macias

Joined: 15 Feb 2014
Posts: 10
Affiliation: Cinvestav

 Posted: May 30 2016 Hi everyone, I have a question about clxg (photons) perturbations. I was comparing the CAMB outcome using w=−1 (labeled 'clxg_lcdm ') and w=−0.99999999999 (labeled 'clxg_lcdm_false'). Of course, I was expecting the spectra to be indistinguishable and they are. However, checking the clxg as function of the scale factor (a), I have found the difference shown in the figure. clxg_a_lcdm.png What may be the reason for this difference? And, Why it takes place at this particular value of a?
Antony Lewis

Joined: 23 Sep 2004
Posts: 1351
Affiliation: University of Sussex

 Posted: May 31 2016 Is this using equations.f90 or equations_ppf.f90?
Omar Ruiz Macias

Joined: 15 Feb 2014
Posts: 10
Affiliation: Cinvestav

 Posted: June 13 2016 It's using 'equations.f90' and 'fixq = 1._dl'.
Antony Lewis

Joined: 23 Sep 2004
Posts: 1351
Affiliation: University of Sussex

Posted: June 13 2016

I think you are probably plotting different things here. With do_late_rad_truncation = T, the photon perturbations are not calculated at late time, so the array element you are outputting will be something else (dark energy perturbation or something else, depending on whether w=−1 and hence whether there are any dark energy perturbations).

The best way to plot parameter evolution is to use the python wrapper
 Code: from matplotlib import pyplot as plt import camb import numpy as np pars = camb.set_params(H0=67.5, ombh2=0.022, omch2=0.122, As=2e-9, ns=0.95) data= camb.get_background(pars) a=10**(np.linspace(-8, 0, 500)) z = 1/a -1 eta = data.conformal_time(z) ev = data.get_time_evolution(1., eta, ['delta_photon']) plt.loglog(a, np.abs(ev))
Omar Ruiz Macias

Joined: 15 Feb 2014
Posts: 10
Affiliation: Cinvestav

 Posted: June 15 2016 thank you, Antony. Now it calculates the photon perturbations at late time.
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