PArthENoPE: Public Algorithm Evaluating the Nucleosynthesis of Primordial Elements
O. Pisanti, A. Cirillo, S. Esposito, F. Iocco, G. Mangano, G. Miele, P. D. Serpico
TL;DR
PArthENoPE is a public Fortran code for computing primordial light-element abundances from Big Bang Nucleosynthesis by solving the Boltzmann network starting from nuclear statistical equilibrium, with explicit treatment of the dimensionless evolution variable $z=m_e/T$ and the electron chemical potential $\phi_e$. It models standard BBN while incorporating non-standard physics through parameters such as $\rho_\Lambda$, $\Delta N_{\rm eff}$, and the neutrino degeneracy $\xi$, propagating their effects into the expansion rate and reaction rates. The framework includes a detailed nuclear reaction network (small, intermediate, complete) and updates to reaction rates, with careful handling of neutrino decoupling to achieve sub-percent accuracy. The code is designed for flexibility and public use, offering interactive and card-driven modes and leveraging the NAG libraries for numerical computation, enabling precise tests of standard and beyond-standard cosmologies against observational data.
Abstract
We describe a program for computing the abundances of light elements produced during Big Bang Nucleosynthesis which is publicly available at http://parthenope.na.infn.it/. Starting from nuclear statistical equilibrium conditions the program solves the set of coupled ordinary differential equations, follows the departure from chemical equilibrium of nuclear species, and determines their asymptotic abundances as function of several input cosmological parameters as the baryon density, the number of effective neutrino, the value of cosmological constant and the neutrino chemical potential. The program requires commercial NAG library routines.