Extensions to the Standard Model: Neutrino Mass, the Strong CP Problem, Grand Unification, and Inflation

While the Standard Model (SM) of particle physics provides an exceptionally accurate description of subatomic interactions up to the electroweak scale, unresolved empirical ob- servations and theoretical puzzles require physics beyond the Standard Model (BSM). These include non-zero neutrino masses and oscillations, the unknown nature of cold dark mat- ter, the baryon asymmetry of the Universe, the Strong CP problem, and the origin of primordial cosmological perturbations. This review synthesizes four foundational, theoret- ically motivated frameworks that can address these phenomena: (i) right-handed singlet Majorana neutrinos and the Type-I seesaw mechanism, (ii) the Peccei-Quinn mechanism and dynamical axions, (iii) SO(10) Grand Unified Theories (GUTs), and (iv) single-field slow-roll inflation. We examine their structural formulations, mathematical consistency, phenomenological consequences, and mutual theoretical interconnections. 1

@article{deceuster2026_74-extensions-to-the,
  title = {Extensions to the Standard Model: Neutrino Mass, the Strong CP Problem, Grand Unification, and Inflation},
  author = {De Ceuster, Peter},
  year = {2026},
  month = {02},
  institution = {SIG Labs},
  doi = {10.5281/zenodo.22162946},
  url = {https://peterdeceuster.uk/papers/74-extensions-to-the-standard-model-neutrino-mass-the},
  note = {Full text available at https://peterdeceuster.uk/articenter/work/extensions.pdf}
}