Cosmology, Relativity, and Gravity Commons^™

Measuring Cosmic Expansion From Early To Late Times Using Quasars, Galaxies, & Local Supernovae, Rajeev Vaisakh

Physics Theses and Dissertations

This dissertation investigates the evolution of cosmic expansion across a wide redshift ($z$) range by combining measurements from quasars \& galaxies in the distant universe $(z > 0.8)$ with those obtained from stripped-core collapse supernovae observations from the nearby universe $(z < 0.1)$. Using the DESI spectroscopic survey, we analyze large-scale clustering from quasars over $0.8 < z < 2.1$ and emission line galaxies over $0.8 < z < 1.6$, contributing to DESI DR2 BAO and full-shape measurements of cosmic expansion and structure growth. Combined with BBN in flat $\Lambda$CDM, DESI DR2 BAO gives $H_0 = 68.51 \pm 0.58$ km s$^{-1}$ Mpc$^{-1}$, while combinations of DESI BAO with CMB and supernova data show a preference for evolving dark energy, with representative constraints such as $w_0 = -0.752 \pm 0.057$ and $w_a = -0.86^{+0.23}_{-0.20}$ for DESI+CMB+DESY5. Using the ROTSE-III Supernova Survey and the expanding photosphere method (EPM), we measure distances to a sample of six supernovae for which the thermal phase can be clearly identified. This analysis focuses on testing whether reliable EPM distances can be obtained for this population. The resulting distances will eventually be compared with independent estimates from the literature. Establishing consistency with these external measurements represents an important step toward applying this methodology to larger samples, with the eventual goal of using ROTSE supernova distances to provide an independent measurement of the local Hubble constant.

Deep Learning Applications For Secondary Cosmic Microwave Background Anisotropies, Eric Guzman

Physics Theses and Dissertations

Next-generation cosmic microwave background (CMB) surveys will map the microwave sky with unprecedented precision presenting a wide range of opportunities for new insights into cosmology. To maximize the scientific value of upcoming surveys, new methods that can disentangle primary and secondary CMB anisotropies are required. The CMB secondaries encode information about the cosmological sources that cause them and act as a source of noise in the observation of primary anisotropies. Quadratic estimators are the current standard techniques for reconstruction of the sources of CMB secondaries. While successful for reconstruction of distortion fields with current data, quadratic estimators will become sub-optimal …

Automated Spectroscopic Detection And Mapping Using Alma And Machine Learningtechniques, Steven Cocke, Andrew Wilkins, Josephine Mcdaniel, John Santerre, Conor Nixon

SMU Data Science Review

In this paper we present a methodology for automating theclassification of spectrally resolved observations of multiple emissionlines with the Atacama Large Millimeter/submillimeter Array (ALMA).Molecules in planetary atmospheres emit or absorb different wavelengthsof light thereby providing a unique signature for each species. ALMAdata were taken from interferometric observations of Titan made be-tween UT 2012 July 03 23:22:14 and 2012 July 04 01:06:18 as part ofALMA project 2011.0.00319.S. We first employed a greedy set cover algorithm to identify the most probable molecules that would reproducethe set of frequencies with respective flux greater than 3σaway from themean. We then selected a subset of …

An Analysis Of Frenkel Defects And Backgrounds Modeling For Supercdms Dark Matter Searches, Matthew Stein

Physics Theses and Dissertations

Years of astrophysical observations suggest that dark matter comprises more than ~80 % of all matter in the universe. Particle physics theories favor a weakly-interacting particle that could be directly detected in terrestrial experiments. The Super Cryogenic Dark Matter Search (SuperCDMS) Collaboration operates world-leading experiments to directly detect dark matter interacting with ordinary matter. The SuperCDMS Soudan experiment searched for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei in low-temperature germanium detectors.

During the operation of the SuperCDMS Soudan experiment, ²¹⁰Pb sources were installed to study background rejection of the Ge detectors. Data from these sources …

Cosmological Distance Measurements With Rotse Supernovae Iip And Observational Systematics On Desi Emission Line Galaxy Clustering, Govinda Dhungana

Physics Theses and Dissertations

Both Supernovae (SNe) and Baryon Acoustic Oscillations (BAO) surveys emerged as complementary probes of the expansion history of the universe in the last few decades. SNe Ia cosmology has reached the systematic limits in the optical surveys. The most frequently occuring SNe Type IIP are emerging as equally rich distance probes for the next generation larger surveys. In this thesis, I highlight the astrophysical observables of these events in the context of ROTSE III SN survey and using the ROTSE SNe IIP sample, I present calibration in the framework of expanding photosphere method (EPM) to use them as cosmological distance …

Edgar Allan Poe’S Cosmology And Natural Theology: A Constructive Postmodern Appreciation, Theodore Walker

Perkins Faculty Research and Special Events

Contrary to some literary classifications, Edgar Allan Poe’s book-length prose poem Eureka is not intended to be fiction. In Eureka Poe was seriously attempting to advance ‘truth’ about the universe. Poe was doing natural science and poetry in the tradition of Samuel Taylor Coleridge and other natural philosophers. Poe’s prose poem is natural scientific astronomy and cosmology, plus natural theology, not science fiction.

Block Preconditioning Of Stiff Implicit Models For Radiative Ionization In The Early Universe, Daniel R. Reynolds, Robert Harkness, Geoffrey So, Michael L. Norman

Mathematics Research

No abstract provided.