Problems in CAMB

[Nicolò Rovazzani]

Hello everyone,

for my thesis work I am studying the ISW effect on the angular power spectrum for temperature fluctuations at low multipoles. In oder to do this, I need to reproduce, very simply with CAMB, the plot in Figure 2 of the following paper: https://arxiv.org/pdf/astro-ph/0307104, by entering the same values for the necessary parameters (I enclose the plot in question). The problem is that what I obtain is not the same as the result in the paper, even though there seems to be nothing wrong in the lines of code (again, I enclose screens of the code and plot). Can you explain why? Thank you very much.

P.S.: The three input files I enter at the beginning differ only in the value of w (the file "planck_2018.ini" contains w=-1, the file "w_06.ini" corresponds to w=-0.6, the file "w_2.ini" corresponds to w=-2).

[Antony Lewis]

CAMB calculates a consistent model, but the bottom plot you show is for no perturbations (defined in an unphysical way in the synchronous gauge). Unless the dark energy is Lambda, you have to have perturbations in a general gauge (as explained in that paper).