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Dissertation
Flexion in gravitation and cosmology
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2024
DOI:
https://doi.org/10.17918/00010656
Abstract
Cosmic flexion, like cosmic shear, is a weak gravitational lensing correlation function whose signal originates from the large-scale structure of the Universe. Building on the observational success of cosmic shear, along with the unprecedented quality of large-scale cosmological datasets, the time is ripe to explore the practical constraints from cosmic flexion. Unlike cosmic shear, which probes a broad region of the matter power spectrum, cosmic flexion is sensitive to small scales (1 to 100 h/Mpc) and therefore can uniquely place constraints on the small-scale matter power spectrum. I present a theoretical formalism I have developed for cosmic flexion, which includes novel flexion-flexion and shear-flexion two-point correlations. Using observations from the first three years (Y3) of Dark Energy Survey (DES) observations, I present the DES Y3 Flexion Catalogue built using the Lenser flexion measurement pipeline. With flexion measurements for 45M galaxies across the DES Y3 footprint, this is the largest such catalogue to date. I use this catalogue to measure cosmic flexion for the first time, where I detect a cosmic shear-flexion signal that is consistent with theoretical predictions to within ~1[sigma] and rejects the null hypothesis to ~3[sigma]. In addition to weak gravitational lensing flexion in general relativity and [lambda]CDM cosmology, I also examine the behavior of flexion due to exotic, single-lens metrics and the cosmological implications of flexion in a modified gravity context. I find that directional flexion can distinguish between the case of a positive or negative convergence where directional shear cannot, and therefore can provide a unique lensing signature for exotic objects with Ellis wormhole-type metrics, which act as gravitational lenses. I also find cosmic flexion to be a unique probe of parametric models of modified gravity, particularly in the case of scale-dependent phenomenological post-general relativity functions.
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Details
- Title
- Flexion in gravitation and cosmology
- Creators
- Evan James Arena
- Contributors
- David M. Goldberg (Advisor)David J. Bacon (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xix, 247 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Physics; Drexel University
- Other Identifier
- 991021890114804721