How to implement a transition in Omega_cdm(a) in CLASS?

[DahmaniSafae]

Hello,

I’m working on a dark matter model with a transition at a specific redshift z_tr. Instead of using a Heaviside function directly, I have used a simple condition in the code like:

if (pba->has_cdm == TRUE) {
if (a > 1./(1.+z_tr)) {
pvecback[pba->index_bg_rho_cdm] = expression_1;
} else {
pvecback[pba->index_bg_rho_cdm] = expression_2;
}

rho_tot += pvecback[pba->index_bg_rho_cdm];
rho_m += pvecback[pba->index_bg_rho_cdm];
p_tot += 0.;
}

My goal is to simulate a transition in the background evolution, and I want to confirm whether this kind of implementation is sufficient within the CLASS framework. Is this conditional statement enough to define a sharp transition in the energy density of dark matter in CLASS, or are there additional changes needed.

Also, is there a recommended way to implement a smooth or sharp Heaviside step in CLASS?

Thank you for your help!