Problem with HST.f90 and using only Sn data.

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Mohsen Khorasani
Posts: 3
Joined: November 22 2018
Affiliation: Shiraz University

Problem with HST.f90 and using only Sn data.

Post by Mohsen Khorasani » July 03 2021

Hi everyone,

1. I want to constrain a model for dark energy using only the background data, e.g. supernovae data. How can I use paramnames_background.paramnames file? Since Ωbh2 and Ω_ch2 have not been included in this file, I fixed both the omega_b.h2 and omega_c.h2 values and left the range for the derived parameter Ω_m in params_CMB.derived_ranges unchanged. Unfortunately, I'm not able to produce contours (even for LCDM) for H_0, Ω_m and ΩΛ like what we see for A. Reiss. Am I missing something here?

2. If I use HST dataset, should I change HST.F90 file for my time dependent dark energy equation of state w=w(a)? It looks like this likelihood is merely for LCDM.

Any help would be appreciated.

Antony Lewis
Posts: 1723
Joined: September 23 2004
Affiliation: University of Sussex
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Re: Problem with HST.f90 and using only Sn data.

Post by Antony Lewis » July 05 2021

For pure background the result only depends on \Omega_m h^2, so \Omega_b h^2 can be fixed to any sensible value. \Omega_c h^2 is then determined via \Omega_m, H_0.

For funny dark energy models the local H0 measurements certainly don't necessarily translate into constraint on H(z=0). It would be better to use a constraint on the magnitude and combine with the supernovae. This is optional provided with Cobaya but not cosmomc by default.

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