I am studying a set of quintessence cosmologies where I struggle to find solutions to the background equations if I demand Ω

_{DE}<~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 Ω

_{DE}<~0.1 today.)

I therefore cannot call CAMB from COSMOMC with Ω

_{DE}~<0.1

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

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```
try_b = 50
call SetForH(Params,CMB,try_b, .true.)
if (CMB%omv >= 0.1) then
D
```_{b_OK} = .true.
D_{b} = CMBToTheta(CMB)
end if
try_t = 100
call SetForH(Params,CMB,try_t)
if (CMB%omv >=0.1 ) then
D_{t_OK} = .true.
D_{t} = CMBToTheta(CMB)
end if
if (D_{b_OK}==.false. .or. D_{t_OK}==.false.) then
CMB%omv=0 ! Reject it
else if (DA < D_{b} .or. DA > D_{t}) then
cmb%H0=0 ! Reject it
else

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

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`if (CMB%Omv < 0.1) return`

_{0}: 50<H

_{0}<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.)

Thanks,

Ewan Tarrant