BBN-simple: How to Bake a Universe-Sized Cake

TL;DR

BBN-simple is an educational numerical tool designed to calculate primordial element abundances in the early universe, making the complex physics of Big Bang Nucleosynthesis accessible for students and beginners.

Contribution

It introduces a simplified, from-scratch computational approach to BBN suitable for pedagogical purposes, contrasting with more technical existing codes.

Findings

Achieves good agreement with established BBN codes

Provides an accessible educational resource

Demonstrates key physics of early universe nucleosynthesis

Abstract

Big Bang Nucleosynthesis (BBN), the process of creation of lightest elements in the early universe, is a highly robust, precise, and ultimately successful theory that forms one of the three pillars of the standard hot-Big-Bang cosmological model. Existing theoretical treatments of BBN and the associated computer codes are accurate and flexible, but are typically highly technical and opaque, and not suitable for pedagogical understanding of the BBN. Here we present BBN-simple -- a from-scratch numerical calculation of the lightest element abundances pitched at an advanced undergraduate or beginning graduate level. We review the physics of the early universe relevant for BBN, provide information about the reaction rates, and discuss computational-mathematics background that is essential in setting up a BBN calculation. We calculate the abundances of the principal nuclear species in a standard cosmological model, and find a reasonably good agreement with public precision-level BBN codes.