CAMB: modifying diffusion physics

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
Post Reply
Graeme Addison
Posts: 27
Joined: July 17 2014
Affiliation: Johns Hopkins University

CAMB: modifying diffusion physics

Post by Graeme Addison » May 26 2019

Is it possible to edit camb/equations.f90 to change the physics of diffusion damping when computing the CMB power spectra, e.g. modify the photon mean free path? My understanding was that the impact of the diffusion damping for some particular k-mode was captured in a multiplicative function [math] that in principle could be separated from other physical effects, but I'm having trouble figuring out from the code whether this is the case.

Antony Lewis
Posts: 1484
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

Re: CAMB: modifying diffusion physics

Post by Antony Lewis » May 26 2019

You'd have to modify the scattering terms for the Boltzmann equation, e.g. most simply by changing the Thomson scattering cross-section. The D(k) is only an approximation and is not used.

Graeme Addison
Posts: 27
Joined: July 17 2014
Affiliation: Johns Hopkins University

Re: CAMB: modifying diffusion physics

Post by Graeme Addison » May 27 2019

Ah OK, I didn't appreciate that was an approximation. Thanks. I guess that means there's no way to modify diffusion physics without also modifying e.g. timing of recombination.

Post Reply