Paul Rogozenski, Physics Graduate Student
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Abstract: The standard model of cosmology, ΛCDM, has shown great flexibility in accurately modeling observations across cosmic time. The increased statistical precision of cosmological surveys in the early 21st century, however, has uncovered potential tensions in cosmological constraints between early- and late-time observables. These tensions can either indicate the breakdown of ΛCDM and require new physics to reconcile observations, or can be induced by insufficient modeling of systematic uncertainties. In this thesis, we primarily focus on the role neutrino-like particles play in cosmological constraints of large-scale structure (LSS) observations. We first summarize the standard model of cosmology, the modeling of neutrinos within ΛCDM, and how LSS surveys (i.e. the Dark Energy Survey and the Legacy Survey of Space and Time) relate observables to the underlying cosmological model. We then take a closer look at the analysis choices of LSS surveys and consider a range of factors that impact consistency checks of the standard model, including: the robustness of Bayesian methods in quantifying tensions, the role of neutrinos in suppressing the small-scale growth of structure, and the impact of additional sterile neutrinos on cosmological constraints. Through these analyses, we address sources of modeling concern and offer new techniques to accurately and precisely account for the impact of both standard-model and sterile neutrinos in LSS observations. We find that current LSS surveys can be more precise with improved models and that current modeling choices can lead to systematic biases of future LSS cosmological constraints.
Zoom: https://arizona.zoom.us/j/86444168896 Password: 474297