Archive for "A conservative Einstein–Boltzmann implementation of an auxiliary scalar perturbation in CLASS"

This archive contains the source code and analysis scripts associated with the article“A conservative Einstein–Boltzmann implementation of an auxiliary scalar perturbation in CLASS”. The repository provides a minimal and explicit extension of the CLASS Einstein–Boltzmann solver implementing an auxiliary scalar perturbation at the level of linear cosmological perturbation theory. The implementation introduces an additional scalar degree of freedom that contributes to the perturbed stress–energy tensor while leaving the background cosmology and Einstein field equations unmodified. The archived materials include: - Modified CLASS source files implementing the auxiliary scalar perturbation,- Configuration (.ini) files used for the numerical runs presented in the paper,- Python scripts used to generate the figures and quantitative diagnostics,- Documentation describing the implementation, usage, and reproduction of results. The purpose of this archive is to ensure full reproducibility of the numerical results and to provide a transparent reference implementation for researchers interested in extending Boltzmann solvers with auxiliary perturbative degrees of freedom. The code is released under the GNU General Public License v3.0 (GPL-3.0), consistent with the licensing of CLASS. This work is intended as a methodological and technical validation of conservative Boltzmann embeddings and does not propose a specific physical interpretation of the auxiliary scalar field.