UWSpaceThe UWSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.https://uwspace.uwaterloo.ca:4432023-09-25T01:48:31Z2023-09-25T01:48:31ZBlack hole dynamics in Effective Field Theory extensions to General RelativityCayuso, Ramirohttp://hdl.handle.net/10012/199242023-09-23T02:31:35Z2023-09-22T00:00:00ZBlack hole dynamics in Effective Field Theory extensions to General Relativity
Cayuso, Ramiro
This thesis aims to develop and implement mathematical and numerical techniques to enable the study of deviations from General Relativity (GR) in the nonlinear regime. The focus is on studying the nonlinear dynamics of higher derivative Effective Field Theory (EFT) extensions to GR and employing innovative methods to address the associated mathematical and practical challenges. To this end, we utilize two crucial techniques: the Fixing the Equations method, which controls spurious high frequencies, and the Order reduction approach to address challenges related to higher than second order time derivatives
and ghosts.
The research starts with a detailed study of black hole dynamics in a higher derivative extension of General Relativity described by a dimension-eight operator EFT. A fully nonlinear/non-perturbative treatment is presented for constructing initial data and studying its dynamical behavior in spherical symmetry when coupled to a massless scalar field.
Subsequently, we extend the previous work to explore the evolution of black holes merging in quasi-circular orbits within the same higher-derivative EFT extension. This scenario poses more demanding challenges; a toy model and the single-boosted black hole scenario are considered to build up to the binary merger case. The effects of modifications
on the dynamics and gravitational wave emission in the binary merger scenario are studied.
The research work culminates with a study of gravitational collapse in Quadratic Gravity, the leading order correction to GR from an EFT perspective in the presence of matter fields. An Order Reduction approach is used to eliminate additional degrees of freedom associated with higher order time derivatives. We study the collapse of a massless scalar field into a black hole in spherical symmetry. We explore the stability of our simulations, whether the solutions remain within the bounds of EFT, and their deviations from General Relativity during the collapse.
2023-09-22T00:00:00ZThe Effects of Uniform Acceleration on the Correlation HarvestingNaeem, Manarhttp://hdl.handle.net/10012/199232023-09-23T02:31:32Z2023-09-22T00:00:00ZThe Effects of Uniform Acceleration on the Correlation Harvesting
Naeem, Manar
Quantum field theory (QFT) in curved spacetime focuses on the analysis of quantum fieldsâ€”representing fundamental particles and their interactionsâ€”within a curved spacetime geometry, accounting for relativistic effects.
Among the prominent subjects in QFT are the Unruh effect and the entanglement harvesting protocol. The Unruh effect, introduced by G. Unruh, posits that a uniformly accelerating particle detector undergoes thermality, despite the absence of particles perceived by an inertial observer. Entanglement harvesting protocol on the other hand involves two or more Unruh-Dewitt (UDW) detectors within a quantum field. It examines the amount of entanglement between these detectors after interacting with the field, which depends on the trajectories of the detectors and the spacetime geometry. Current studies are expanding into other correlation types, collectively referred to as the correlation harvesting protocol.
In this thesis, we investigate the effects of uniform acceleration on the correlation harvesting protocol, with a particular emphasis on understanding the impact of Unruh temperature on the total correlation harvesting. A prior investigation explored the correlation harvesting protocol for two inertial UDW detectors in a thermal bath. The findings revealed that high temperatures inhibit entanglement harvesting between the detectors, while it enhances the total correlation between them. We investigate whether the Unruh temperature induces a similar impact on correlation harvesting by examining the correlation harvesting protocol of two linearly uniformly accelerating UDW detectors. We then broaden our investigation to encompass other uniformly accelerating trajectories, initially defined by Letaw, that could induce effects similar to the Unruh effect but might be more feasible than linear motion in an experimental setting, This is particularly relevant in consideration of ongoing experiments aiming for Unruh effect verification.
Our findings are as follows: (i) high accelerations(equivalently Unruh temperature) prevent the detectors from acquiring correlations from the field in all trajectories of detectors that are uniformly accelerating. (ii) Within the framework of uniform acceleration, there exists small, yet consequential, regions of parameter space where detectors in causal contact may genuinely harvest entanglement. (iii) The Unruh temperature's effect on total correlation harvesting diverges from that of thermal bath temperature despite their similar effect on a single detector.
2023-09-22T00:00:00ZSynthesis of Molybdenum-Based Nanomaterials with High Photothermal Conversion Efficiencies by Femtosecond Laser Ablation in LiquidYe, Fanhttp://hdl.handle.net/10012/199222023-09-23T02:31:30Z2023-09-22T00:00:00ZSynthesis of Molybdenum-Based Nanomaterials with High Photothermal Conversion Efficiencies by Femtosecond Laser Ablation in Liquid
Ye, Fan
Photothermal therapy is a novel cancer treatment that can be an alternative or useful supplement to traditional cancer treatments. It relies on nanomaterials which target and accumulate in tumor cells to absorb near infrared light and convert the absorbed light energy into heat to kill tumors. Therefore, it is important to prepare nanomaterials with high photothermal conversion efficiencies (PTCEs). Pulsed laser ablation in liquid is a novel technique to prepare nanomaterials. In this work, this technique is used to prepare molybdenum-based nanomaterials including substoichiometric molybdenum oxide (MoO3-X) nanosheets, molybdenum blue (MB) nanorings, and molybdenum selenide (MoSe2) spherical nanoparticles and quantum dots.
MoO3-X and MB nanorings are produced by laser ablation of MoS2 powder and MoO3 powder in water/ethanol mixtures, respectively. The oxidation process of MoS2 and the formation mechanism of MB nanorings are studied. In both ablation processes, ethanol plays a critical role in reducing Mo(VI) which results in the blue color of MoO3-X and MB nanorings. 80-90 vol.% ethanol is the optimum to produce blue-colored MoO3-X, while 30 vol.% ethanol is the optimum to produce MB nanorings with the darkest blue color. A higher concentration of ethanol in the solvent results in the formation of MoO3-X instead of MB. The MoO3-X nanosheets show a high PTCE of 33%, and the MB nanorings show a PTCE as high as 45%.
MoSe2 spherical nanoparticles are produced by laser ablation of MoSe2 powder for a short time (10 min) in isopropyl alcohol or in water containing polyethylene glycol (PEG). The spherical nanoparticles are fragmented from ablated powder particles based on two primary approaches. The first one is thermodynamic equilibrium melting and evaporation which usually occurs when the ablation power is low. The second one is explosive boiling when the ablation power is high. Two kinds of spherical nanoparticles, including polycrystalline nanoparticles and onion-structured nanoparticles, are observed. The polycrystalline nanoparticles are primarily formed by the agglomeration of nanocrystals, atoms and ions ejected from the ablated powder. The onion-structured nanoparticles are formed by nucleation on the surface of melted droplets followed by inward growth of {002} planes of MoSe2 along the radial direction of the droplets layer-by-layer. Additionally, PEGylated MoSe2 nanoparticles can be directly produced by ablating MoSe2 power in aqueous PEG solutions. The surface attachment of PEG to the nanoparticles via Mo-O chemical bonds can suppress oxidation of the nanoparticles. The MoSe2 nanoparticles show high PTCEs of around 38-40% thanks to strong sub-bandgap photon absorption.
Smaller PEGylated MoSe2 quantum dots are synthesized by laser ablation with a high power (1.5 W) for a longer time (30 min). The PTCEs of the PEGylated quantum dots are around 42-44%, higher than that of the PEGylated spherical nanoparticles, which is probably due to a larger absorption cross-section, multiple exciton generation and multiple electron-decay channels.
2023-09-22T00:00:00ZCharacterizing the Dynamics of Otto Glacier, Ellesmere Island, Canadian High Arctic: 1992-2020Wagner, Monikahttp://hdl.handle.net/10012/199212023-09-23T02:31:27Z2023-09-22T00:00:00ZCharacterizing the Dynamics of Otto Glacier, Ellesmere Island, Canadian High Arctic: 1992-2020
Wagner, Monika
The mass loss observed from glaciers in the Canadian Arctic is unprecedented over recent decades (Hugonnet et al., 2021) and is the third largest contributor to global sea level rise (Derksen et al., 2019). One way in which glaciers lose mass to the ocean is through dynamic discharge, which involves the calving of icebergs to the ocean. Glacier dynamics in the Canadian Arctic have undergone limited study, especially surge-type glaciers, which oscillate between periods of fast flow and slow flow. Detailed studies of individual surge-type glaciers can enhance knowledge of how and why glaciers surge. As such, this thesis analyzed the surge cycle of Otto Glacier on northern Ellesmere Island in Nunavut, Canada, from 1992-2020. The analysis included velocity measurements from 1992-2020, which used data from optical and radar imagery. Three phases were identified for the study period: the fast flow phase (1992-2008), the deceleration phase (2009-2017), and the quiescent phase (2018-2020). Maximum velocities occurred within the lowermost ~6 km of the glacier during the fast flow phase (700-1300 m/yr), and minimum velocities (1-80 m/yr) were noted along the entire glacier during the quiescent phase. Terminus extent, analyzed with optical and radar imagery, advanced by 1545 m during the fast flow phase, and retreated by 1408 m by the end of the quiescent phase. Rates of glacier surface elevation change, obtained from pre-generated elevation products by Hugonnet et al. (2021), showed surface elevation lowering in the lowermost ~6 km of the glacier and thickening upglacier that was progressive over the study period. Analysis of bedrock topography found a v-shaped sill spanning ~4-8 km upglacier from the terminus, which was inferred to have influenced terminus retreat, glacier thickness, and subsequently velocity variability. The findings provide a detailed characterization of the surge cycle phases for Otto Glacier and suggest a possible surge mechanism, which has not previously been explored in depth.
2023-09-22T00:00:00Z