AlterBBN: A program for calculating the BBN abundances of the elements in alternative cosmologies

We describe AlterBBN, a public C program for evaluating the abundances of the elements generated by Big-Bang Nucleosynthesis (BBN). This program enables the user to compute the abundances of the elements in the Standard Model of cosmology, and additionally provides possibilities to alter the assumptions of the cosmological model in order to study their consequences on the abundances of the elements. In particular the baryon-to-photon ratio, the effective number of neutrinos and the neutron lifetime, as well as the expansion rate and the entropy content of the Universe during BBN can be modified in AlterBBN. Such features allow the user to test the cosmological models by confronting them to BBN constraints. A presentation of the physics of BBN and the features of AlterBBN is provided here under the form of a manual. Program summary Program title: AlterBBN Catalogue identifier: AEMH_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMH_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Gnu General Public License version 3 No. of lines in distributed program, including test data, etc.: 4611 No. of bytes in distributed program, including test data, etc.: 44 657 Distribution format: tar.gz Programming language: C (C99 Standard compliant) Computer: 32- or 64-bit PC, Mac Operating system: Linux, MacOS RAM: 100 Mb Classification: 1.2, 1.9 Nature of problem: Calculation of the abundances of the elements during Big-Bang Nucleosynthesis (BBN). Solution method: AlterBBN computes the abundances of the elements by integrating the BBN differential equations thanks to a second-order Runge-Kutta method, obtaining a matrix equation from implicit differencing and solving this equation using Gaussian elimination. Unusual features: AlterBBN includes the possibility of altering the underlying cosmological model and testing the influence of the cosmological assumptions on the abundances of the elements. Uncertainties can be evaluated by computing the abundances of the elements using lower or higher limits of the nuclear reaction rates. Running time: Compilation: Less than 1 minute. Running: Less than 1 second. (C) 2012 Elsevier B.V. All rights reserved.