Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 15 of 15 for “"21 cm cosmology"”.
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Quantum money and scalable 21-cm cosmology
… theory. The second part of my thesis is about 21-cm cosmology and the Fast Fourier transform telescope. With the FFT telescope group at MIT, I worked on a design for a radio telescope that operates between 120 and 200 MHz and will scale to an extremely large number of antennas N. We use an …
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21 cm cosmology with optimized instrumentation and algorithms
Precision cosmology has made tremendous progress in the past two decades thanks to a large amount of high quality data from the Cosmic Microwave Background (CMB), galaxy surveys and other cosmological probes. However, most of our universe's volume, corresponding to the period between the CMB and …
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Instrumental Effects in 21 cm Cosmology: One-point Statistics and Power Spectrum with the HERA Interferometer
… the EoR involves observing the redshifted 21 cm line emission with radio telescopes. A significant challenge in this endeavor is isolating the faint 21 cm signals from bright foreground emissions and systematics. This collection of works focuses on understanding the impact of instrumental …
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Initial exploration of 21-cm cosmology with imaging and power spectra from the Murchison Widefield Array
… goal of measuring the power spectrum of the 21-cm signal from neutral hydrogen during the Epoch of Reionization (EoR). In this thesis, we detail efforts to characterize the MWA system, and present scientific results from a 32-element prototype interferometer deployed at the MWA site. We …
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It's always darkest before the cosmic dawn : early results from novel tools and telescopes for 21 cm cosmology
21 cm cosmology, the statistical observation of the high redshift universe using the hyperfine transition of neutral hydrogen, has the potential to revolutionize our understanding of cosmology and the astrophysical processes that underlie the formation of the first stars, galaxies, and black holes …
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Simulation-based Bayesian machine learning methods for Cosmology and beyond
… Bayesian inference in sky-averaged 21-cm Cosmology. Moreover, PolySwyft merges nested sampling and neural ratio estimation into a general Bayesian framework, and the method is a general-purpose algorithm applicable beyond Cosmology. This thesis is divided into five sections. In the …
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Absolute Flux Density Measurement and Associated Instrumentation for Radio Astronomy below 100 MHz
… of contemporary interest in radio astronomy and 21 cm cosmology in this frequency range. A new active antenna system and measurement technique were developed to facilitate these measurements. The antennas are simple, thin dipoles, allowing for accurate characterization. Amplification is preceded …
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Data Analysis in Global 21-cm Experiments: Chromatic Effects and Signal Reconstruction
… chromatic effects that can distort the global 21-cm signal and introduces a flexible signal model designed to capture potential features arising from unexpected physics. The work is carried out within the framework of the REACH experiment and its data analysis pipeline. Part I includes two …
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Constraining reionization: Evidence from 21 cm limits and predictions for fast radio bursts
… the reionization history, and the global 21 cm signal. Specifically, I use upper limits on the 21 cm power spectrum measured by the HERA interferometer, current and future measurements of the global 21 cm signal, and forecasts for high redshift Fast Radio Bursts (FRBs). Firstly, I examine …
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Probing the First Stars with the 21-cm Signal: Theory, Methods, and Forecasts
… their mass distribution, using the cosmological 21-cm signal. We begin in Part I by introducing the first stars, 21-cm cosmology, and the link between them (Chapter 1), as well as describing in detail the semi-numerical 21-cm signal simulation code 21cmSPACE, used throughout this thesis (Chapter …
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Robust Statistical Radio Interferometric Methods for the Detection of the Epoch of Reionization
In 21 cm cosmology, we are seeking to detect the highly redshifted spin-flip line of HI to constrain the properties of the Epoch of Reionization and to better understand the astrophysical and cosmological processes of the early Universe. The sensitivity requirements for such a detection are …
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Numerical modelling and design of wideband electromagnetic structures at radio frequencies: Applications in cosmology and digital communications
… of computational electromagnetics to the global 21 cm experiment REACH. This experiment aims to detect a signal five orders of magnitude below the foreground signal, and so requires highly accurate and precise understanding of the radiometer instrument. Both the design and analysis of aspects of …
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Investigating the Epoch of Cosmic Reionisation with Radio Interferometers
… promising probe of the EoR is the redshifted H I 21 cm line, which has the potential to characterise the 3-dimensional distribution of neutral hydrogen. The statistical detection of its spatial fluctuations is a prime objective of modern low-frequency radio interferometers, though instrumental …
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The Bayesian Global Sky Model (B-GSM)
Observations of the redshifted 21-cm signal of neutral hydrogen gas from the first billion years after the Big Bang have the potential to inform studies of cosmic structure formation and fundamental physics research [3, 5]. This signal is today visible at frequencies in the range 50-200~MHz. …
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Fundamental physics from observations of the early universe
The current experiments like Planck and future CMB, 21-cm and other large scale structure surveys will enable cosmology to answer some of the fundamental questions in physics. The linear perturbation theory may not be accurate enough to interpret the observations from Planck and future CMB …