Modeling Astrophysical and Large-Scale Structure Signatures in Axion Cosmologies
type: CreativeWork
description: The quest to understand the fundamental nature of dark matter (DM) remains a challenge in contemporary physics. This thesis aims at elucidating astrophysical and cosmological imprints of fuzzy dark matter (FDM), a promising class of models which find ample motivation within theories of particle physics. Notably, the string axiverse hypothesis posits the existence of a multitude of pseudoscalar particles called axions with logarithmically distributed masses, potentially addressing both the DM and dark energy problems simultaneously. Combining theoretical analyses with numerical simulations, we unravel the distinct signatures of FDM across intergalactic and group/cluster scales. We begin by studying density, shape and weak lensing statistics in FDM cosmologies, finding strong departures from the universality of density profiles and the monotonicity of shape profiles observed in the vanilla cold dark matter (CDM) model. Our first-ever analysis of geometric and intrinsic alignments in FDM cosmologies reveals increased alignment strengths compared to CDM, holding particular relevance for weak lensing surveys like Euclid, and we embed our findings into a wider weak lensing analysis to predict convergence and ellipticity spectra. By publishing the COSMICPROFILES Python package we enhance reproducibility and accessibility of our results. To reveal the morphology of the cosmic web, we then apply an advanced segmentation algorithm (NEXUS+). We report high mean densities of filaments, sheets and voids in FDM compared to CDM, while cosmic skewness estimates also increase, which could be used as a testbed for constraining FDM. Moving to astrophysical implications, we deploy generative machine learning models (normalizing flows) to characterize neutral hydrogen distributions in post-reionization FDM model Universes. Our findings indicate that extreme FDM models can be ruled out based solely on their low neutral hydrogen (HI) abundance. We quantify the HI and damped Lyman-𝛼 (DLA) …
abstract: The quest to understand the fundamental nature of dark matter (DM) remains a challenge in contemporary physics. This thesis aims at elucidating astrophysical and cosmological imprints of fuzzy dark matter (FDM), a promising class of models which find ample motivation within theories of particle physics. Notably, the string axiverse hypothesis posits the existence of a multitude of pseudoscalar particles called axions with logarithmically distributed masses, potentially addressing both the DM and dark energy problems simultaneously. Combining theoretical analyses with numerical simulations, we unravel the distinct signatures of FDM across intergalactic and group/cluster scales. We begin by studying density, shape and weak lensing statistics in FDM cosmologies, finding strong departures from the universality of density profiles and the monotonicity of shape profiles observed in the vanilla cold dark matter (CDM) model. Our first-ever analysis of geometric and intrinsic alignments in FDM cosmologies reveals increased alignment strengths compared to CDM, holding particular relevance for weak lensing surveys like Euclid, and we embed our findings into a wider weak lensing analysis to predict convergence and ellipticity spectra. By publishing the COSMICPROFILES Python package we enhance reproducibility and accessibility of our results. To reveal the morphology of the cosmic web, we then apply an advanced segmentation algorithm (NEXUS+). We report high mean densities of filaments, sheets and voids in FDM compared to CDM, while cosmic skewness estimates also increase, which could be used as a testbed for constraining FDM. Moving to astrophysical implications, we deploy generative machine learning models (normalizing flows) to characterize neutral hydrogen distributions in post-reionization FDM model Universes. Our findings indicate that extreme FDM models can be ruled out based solely on their low neutral hydrogen (HI) abundance. We quantify the HI and damped Lyman-𝛼 (DLA) …
author: Döme, Tibor
language: eng
keywords: cosmology, large-scale structure of Universe, dark matter, galaxy formation and evolution, axion cosmology
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/912c0385-b523-4aaf-90e0-fa99b68dde69/download
license: https://creativecommons.org/licenses/by/4.0/
date published: 2024-03-01
date modified: 2026-07-22T22:24:25Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.111401