CosmoCoffee

[Omar Ruiz Macias]

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]

Is this using equations.f90 or equations_ppf.f90?

[Omar Ruiz Macias]

It's using 'equations.f90' and 'fixq = 1._dl'.

[Antony Lewis]

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

[Omar Ruiz Macias]

thank you, Antony. Now it calculates the photon perturbations at late time.