CAMB: radiation contribution in the expansion rate

[Carmelita Carbone]

Hi all,

is there an easy way to cut the photon contribution to the expansion rate in camb for z<99 ? I had a look at equations.f90 and modules.f90, and tried to cut the term grhog from grho and grhoa2 for a>1/100, but it seems not working...

The point is that for an accurate comparison with Nbody simulations, one needs to exclude Omega_gamma in H(z), at least when not using the lastest gadget-3 version.

Let me know please...

Thanks,
Carmelita

[Antony Lewis]

Presumably you'd also want to exclude the neutrino radiation density. I'd have though setting things derived from ghrog and grhor temporarily to zero in equations.f90 would work (but don't change the value globally or the next k will be wrong).

But there may also then be some mismatch in initial conditions if the N-body code assumes things start in the growing mode at high redshift (?).