Fit early-ish dark energy models to background distance/expansion rate data. This code was used to produce the plots in arXiv:2007.02865.

• numpy, scipy, matplotlib
• pyccl (for some test functions)
• emcee

This code is meant to be used with Fisher matrices output by RadioFisher. Some example matrices are included in this repository. These matrices model the covariances for the angular diameter distance and expansion rate for a set of redshift bins. Nuisance parameters, such as bias and growth rate, may also be included.

You can, however, modify the code to use whatever likelihood function you want. Simplified Planck data (i.e. using shift parameters; see arXiv:2007.02865) are also included here for example.

To run this code, use the fit_wztanh.py script. This runs an emcee MCMC chain using particular experimental settings. It's best to inspect the code to see what settings can be changed. The code does run on multiple cores.

The dark energy models themselves are defined in wztanh.py.

A variety of plotting scripts are also provided. The main one is plot_bounds_all.py. The plot_obs_errors.py script is also useful for inspecting the constraints implied by the various Fisher matrices.

• For all of the results generated before 2020-06-15, there was a minus sign bug in the definition of the Tracker model 'deltaw' parameter (if used). It works out so that 'deltaw' in these runs is actually '-deltaw'. This bug has now been fixed (but double-check the code).