Automated calculation of spin–isospin branching rules for SU(4) irreps
Description
The open-source Python package su4-branching automates the derivation of comprehensive spin S and isospin T branching rules for SU(4) irreducible representations. The Wigner supermultiplet scheme underlying nuclear and hadronic physics depends critically on SU(4) symmetry. However, practical calculations of branching rules for arbitrary SU(4) irreps have been largely inaccessible to the research community. Our implementation combines Racah’s tensor contraction formula with Python modularity, enabling straightforward exploration of high-dimensional SU(4) irreps through interactive Jupyter interfaces and multiple export formats. Comprehensive validation against three independent reference frameworks (Quesne 1976; Patera 1981; Pan et al. 2024) and dimensional consistency checks (necessary and sufficient for correctness) demonstrate reliability across dimensions 1–10^7. This work enables systematic group-theoretical investigations in nuclear structure, particle physics, and quantum chemistry.