Date of Award

Spring 4-28-2026

Document Type

Honors Project

Degree Name

Bachelor of Science

Department

Chemistry and Physics

Department Chair or Program Director

Nicole Crowder

First Advisor

Desmond Villalba

Major or Concentration

Physics

Abstract

This work considers an extra-dimensional framework to explain the gravitational wave background (GWB), massive neutrinos, and baryon asymmetry. Through studying all three, restrictions on certain parameters arise and provide bounds on both theories. It is proposed that the GWB is caused by cosmic domain walls, sheet-like topological defects that were theoretically created in the early universe shortly after the Big Bang. A relationship be- tween the energy density of domain walls and the vacuum expectation value of the broken symmetry was defined. Constraints on the parameters, including the already observed fre- quencies of gravitational waves and the current energy content of our universe, restrict the predicted GW amplitudes to an upper limit of Ωh2 < 10−21. The extra-dimensional seesaw mechanism was considered and the non-unitarity on the leptonic mixing matrix was tested against the bound of experimentally determined limits. No restriction was found based on the non-unitarity. Further, a baryogenesis scenario was considered and the known baryon asymmetry was used to determine the bounds on parameters. Finally, these restrictions are then applied to the GW parameter space, and it was found that the proposed scalar field cannot cause both the GWB and the baryon asymmetry.

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