This code "nudec_BSM_v2" provides a fast and flexible description of neutrino decoupling in the early universe following the momentum-averaged approach. Independent Mathematica and Python implementations are provided, and should be easy to link with other codes, e.g. for BBN. The latest version has been developed by M. Escudero, G. Jackson, M. Laine and S. Sandner in 2511.04747 (extending the earlier v1 from M. Escudero in 1812.05605 and 2001.04466). The main module files are stored in the directory BasicModules_source/, each with a preamble of documentation giving more details about the included functions and their options.
As of 10/11/2025:
New version 2 of the code imported under branch v2.
This version is compatible with Python3 and contains the following scripts:
-
test.py: Minimal example file that shows how to import and run the basic models in Python. -
nudec.ipynb: Jupyter notebook walkthrough, including several plots. -
BasicModules_source/nudec_v2.py: Main source file, includes classes needed to solve for neutrino decoupling.
The Mathematica version contains the following scripts:
-
Neff_SM.nb: Contains several illustrations of how to import and run the modules in Mathematica. -
BasicModules_source/nudec_v2.m: Mathematica package file (see also notebook with same name).
Stored under BasicModules_data/. This includes the electron mass dependent (linear response) coefficients for neutrino interaction rates, as well as the interacting QED pressure (as a function of temperature, up to order e5) and its first two derivatives. See section 8 of 2511.04747 for more details.