Modifier: Zilu (Tony) Zhou
Adapted from the CLASS (Cosmic Linear Anisotropy Solving System) code developed by Julien Lesgourgues, Thomas Tram, Nils Schoeneberg and collaborators.
On top of full base CLASS species and utilities (as of interacting dark matter commit on 03/29/2022), this modified version of CLASS contains a new interacting dark radiation specie that contains a "step" in the history of its perturbation growth. The current implementation of one such specie follows the "Wess-Zumino Dark Radation" (WZDR) model considered in Aloni et al. (2022), but more stepped fluid species will be added.
All modifications to CLASS source files are enclosed in comments that read "Stepped fluid modification". All functions and parameters related to the stepped dark radiations have names containing "stepped_fld". The major implementations are contained in the background and perturbation modules.
Installation, compiling and setting up the Python wrapper all work identically to base CLASS. See the official CLASS repository
https://github.com/lesgourg/class_public
for detailed guide on installation. If you run into trouble installing/running the code but can otherwise run base CLASS, please open an issue.
A sample input with the WZDR can be found in inputs/WZDR.ini, and contains some information on how to pass in stepped fluid parameters. After compiling the C code using make
, run
./class input/WZDR.ini
to do a sample run with the WZDR. The code can be used in Python with successful setup of the Python wrapper. Parameter names input in Python should match those in the WZDR.ini file. The Python code is compatible with MontePython.
Like base CLASS this code is open source. Feel free to create a new branch and modify as you please. If you use this code and the WZDR for your work, please include:
- Base CLASS citation
CLASS II: Approximation schemes <http://arxiv.org/abs/1104.2933>
- WZDR citation
A Step in Understanding the Hubble Tension <http://arxiv.org/abs/2111.00014>
- A link to this GitHub repository.