Doctor of Philosophy, Case Western Reserve University, 2021, Physics
One of the most outstanding questions in fundamental physics is the nature of dark matter (DM). From multiple independent sources of evidence we infer that DM exists and constitutes nearly 85% of all matter in the universe. However, it is still not known what comprises the DM, how it is formed, and if and how it interacts non- gravitationally with Standard Model particles. In this dissertation, we are by and large concerned with the final question among the aforementioned list of puzzles, i.e., what signatures can DM leave in the observable universe?
We propose a new mechanism by which DM can affect the early and late universe. The hot interior of a macroscopic DM, or macro, can behave as a heat reservoir so that energetic photons and neutrinos are emitted from its surface and interior respectively. In Part 1 of this dissertation we focus on the spectral distortions (SDs) of the cosmic microwave background before recombination. The SDs depend on the density and the cooling processes of the interior, and the surface composition of the macros. We use neutron stars as a straw-man for nuclear-density macros and find that the spectral distortions are mass-independent for fixed density. In our work, we find that, for macros of this type that constitute 100% of the dark matter, the μ and y distortions can be near or above detection threshold for typical proposed next-generation experiments such as PIXIE.
In Part 2, we study the change in recombination history of hydrogen in the uni- verse caused by macros. We numerically solve the Boltzmann equation to calculate the photon distribution function, electron fraction, and baryonic matter tempera- ture as a function of redshift. During recombination, the excess photons emitted by macros have frequencies well above the excitation and ionization energies of the hydrogen atom. At such high frequencies, the excitation and ionization processes have extremely small cross-sections, thereby limiting the efficiency of the excess p (open full item for complete abstract)
Committee: Glenn Starkman (Advisor); Idit Zehavi (Committee Member); John Ruhl (Committee Member); Stacy McGaugh (Committee Member)
Subjects: Astrophysics; Physics