Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




Andre Walker-Loud

Committee Members

Henry Krakauer

Bruce Campbell


We perform a quantitative study of the sensitivity of Big Bang Nucleosynthesis (BBN) to the two sources of isospin breaking in the Standard Model (SM), the splitting between the down and up quark masses, delta_q = 1/2 (m_d - m_u) and the electromagnetic coupling constant, alpha_fs. To very good approximation, the neutron-proton mass splitting, delta m = m_n - m_p, depends linearly upon these two quantities. In turn, BBN is very sensitive to m. A simultaneous study of both of these sources of isospin violation had not yet been performed.

Quantifying the simultaneous sensitivity of BBN to delta_q and alpha_fs. is interesting as delta m increases with increasing delta_q but decreases with increasing alpha_fs. A combined analysis may reveal weaker constraints upon possible variations of these fundamental constants of the SM. To perform this study, we utilized the latest results from lattice QCD calculations of delta m to quantify the connection between delta_q, alpha_f.s. and BBN.

In order to undertake this project, the existing BBN code, written in FORTRAN, has been updated to allow for string replacement from Python as well as by incorporating rates specifically designed for this variation. This has resulted in a more user-friendly implementation of the variation of various input parameters, such as alpha_fs and delta_q, allowing future studies to be conducted much more easily than before possible and with a greater scope brought by the ability to vary parameters simultaneously.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

On-Campus Access Only