COSMOMC: Prior on ΩDE>0.1

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Ewan Tarrant
Posts: 1
Joined: November 22 2010
Affiliation: University of Sussex

COSMOMC: Prior on \\Omega_{DE}>0.1

Post by Ewan Tarrant » November 22 2010

Dear All,

I am studying a set of quintessence cosmologies where I struggle to find solutions to the background equations if I demand ΩDE<~0.1 today. (For particular parameter values in the quintessence potentials I can find no initial conditions for the quintessence field and initial CDM density if I demand ΩDE<~0.1 today.)

I therefore cannot call CAMB from COSMOMC with ΩDE~<0.1

To get around the issue I have modified subroutine ParamsToCBMParams (params_CMB.f90):

Code: Select allp>

try_b = 50
call SetForH&#40;Params,CMB,try_b, .true.&#41;
if &#40;CMB%omv >= 0.1&#41; then
   Db_OK = .true.
   Db = CMBToTheta&#40;CMB&#41;
end if

try_t = 100
call SetForH&#40;Params,CMB,try_t&#41;
if &#40;CMB%omv >=0.1 &#41; then
   Dt_OK = .true.
   Dt = CMBToTheta&#40;CMB&#41;
end if

if &#40;Db_OK==.false. .or. Dt_OK==.false.&#41; then
   CMB%omv=0 ! Reject it

else if &#40;DA < Db .or. DA > Dt&#41; then
   cmb%H0=0 ! Reject it


and have hardcoded the prior in function GetLogPrior (calclike.f90):

Code: Select allp>

if &#40;CMB%Omv < 0.1&#41; return
I have also tightened the prior on H0: 50<H0<100

Is there anything wrong with this approach?

( I have run this modified code with a standard LCDM cosmology, keeping the default parameter limits in params.ini for COSMOMC, apart from the SZ template normalization which I do not vary. Comparing the results obtained from this run with results obtained from an unmodified COSMOMC, all is as I would expect.)


Ewan Tarrant

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