## CAMB: Forcing code to use same Neutrino Boltzmann Equations for all Tau

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
Benjamin Horowitz
Posts: 3
Joined: October 28 2016
Affiliation: UC Berkeley

### CAMB: Forcing code to use same Neutrino Boltzmann Equations

I'm having a hard time getting some Boltzmann equations that worked in CLASS working in CAMB. My equations should be valid for all tau and shouldn't be subject to the "switches" that are found in the equations.f90. However, whenever I try to deactive switches the behavior becomes very unpredictable (I assume due to the ways ayprime is indexed).

Is there a nice way to just use the equation from lines 2263−2302 from equations.f90 for the entire evolution without having it switch back and forth from various approximations?

Antony Lewis
Posts: 1353
Joined: September 23 2004
Affiliation: University of Sussex
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### Re: CAMB: Forcing code to use same Neutrino Boltzmann Equati

You can set massive_nu_approx=0. However it will still do switches between relativistic regime; to turn off that you'd have to do something like edit the GetNumEqns ( you want nq equal to nqmax I think, but may need further changes).

Benjamin Horowitz
Posts: 3
Joined: October 28 2016
Affiliation: UC Berkeley

### CAMB: Forcing code to use same Neutrino Boltzmann Equations

Great, got it to work!

For all those coming across this in the future; it seems like forcing EV%nq(nu_i)=nqmax, EV%nu_nonrelativistic(nu_i) = .true. , and manually overriding the "Massless neutrino equations of motion"-part of the derivs subroutine had the correct effect.