Abstract

The Standard Model of particle physics and cosmology is amazingly successful in describing our universe, from at present to even tracing back to just one second after its birth. Yet, it is known to be incomplete. For instance, (i) more than four-fifths of matter in the universe is unknown, (ii) quantum chromodynamics is unnaturally of CP-preserving nature, (iii) the universe produced baryonic particles by nearly equal but slightly larger amount compared to anti-baryonic particles, and (iv) the physics at very early times is not understood yet. This thesis first briefly summarizes the Standard Model of particle physics and cosmology, and then, its limitations and potential solutions: the QCD axion, the sterile neutrino, the Affleck-Dine baryogenesis, and the curvaton inflation. Lastly, the author's previous work is described. The QCD axions and axion-like particles spontaneously and/or are stimulated to decay to two photons. We estimated the detectability of photons from Galactic QCD axion dark matter particles and keV-MeV axion-like particles produced in heavy stars. In addition, we estimated the capture rate of keV sterile neutrino dark matter by a compact astrophysical object and estimated the subsequent cooling/heating effect. The last part of this thesis discusses the viability of the curvaton inflationary scenario where a nonzero baryon number is produced via the Affleck-Dine mechanism.

Committee Chair

Francesc Ferrer

Committee Members

Alexander Chen; Bhupal Dev; James Buckley; Renato Feres

Degree

Doctor of Philosophy (PhD)

Author's Department

Physics

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

8-15-2025

Language

English (en)

Author's ORCID

https://orcid.org/0009-0003-9478-380X

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