ℋ- EFTCAMB : a Cobaya-integrated, Python-wrapped extension of EFTCAMB for covariant Horndeski gravity

Abstract We present ℋ- EFTCAMB , the official successor to EFTCAMB . The original EFTCAMB is designed as a consistent and numerically stable implementation of the effective field theory (EFT) of dark energy in the Einstein-Boltzmann code CAMB . On top of this, ℋ- EFTCAMB introduces a new Horndeski module that supports computing cosmology for an arbitrary input covariant Horndeski Lagragian. ℋ- EFTCAMB supports both mapping the Horndeski theory to an EFT lagrangian to solve in the EFT framework as well as directly solving for the scalar field equations of motion derived from the covariant Lagrangian. The latter approach also works for the cases when the Horndeski field experiences turn-overs, e.g. oscillation, where the EFT approach breaks down. The Horndeski module has been validated by comparing internally with existing models in the original EFTCAMB and externally with hi_class . ℋ- EFTCAMB features a flexible Python wrapper that is seamlessly integrated into the widely utilized cosmological sampler Cobaya . ℋ- EFTCAMB is publicly available and serves as a comprehensive tool for testing gravity against the precision data from current and next-generation surveys. ℋ- EFTCAMB is publicly available at this URL .