New Tricks for Old Stars: Studying Compact Objects Through Novel Methodologies in Timing, Energy and Imaging

Event Time: Wednesday, September 18, 2024 | 10:00 am - 12:00 pm
Event Location:
Henn 309
Add to Calendar 2024-09-18T10:00:00 2024-09-18T12:00:00 New Tricks for Old Stars: Studying Compact Objects Through Novel Methodologies in Timing, Energy and Imaging Event Information: To understand astronomical objects and their environments, it is essential to study their behavior across time, energy and space. For compact objects, these analyses provide a unique window into physics in extreme environments, probing transient behavior, accretion processes, and tests of spacetime and gravity in the high field regime. In this thesis, I present novel approaches to revolutionize timing and spectral analysis and imaging with polarimetry in astronomy. I first present two novel methodologies for astronomical timing analysis: 1) Wiener Deconvolution to resolve the response function generating time lags across different energy bands and 2) Mutual Information as a powerful tool to identify time lags without assuming underlying linearity. I establish methodological framework and demonstrate efficacy of methodologies through toy models for generalized utilization of astronomical timing and lag analysis. I then present the results of novel methodologies applied to radio data from the black hole binary MAXI J1820+070. These approaches not only help in identifying time lags with much higher accuracy and precision, but also reveal numerous previously undetected lags, offering new insights into how the compact jet in MAXI J1820+070 behaves across different energies. I then extend the astronomical application of Wiener Deconvolution to 2D, enabling estimates of the first ever high resolution X-ray polarimetry images, and present preliminary results for the Supernova Remnant Cas A. Finally, I explore magnetar spectral line analysis and modeling, and show how we can learn about the behaviour of magnetic fields at their most intense through spectral lines detected from magnetars with current and future detectors. Event Location: Henn 309

Electrodynamics of Non-topological Solitons

Event Time: Wednesday, September 18, 2024 | 1:30 pm - 3:30 pm
Event Location:
Henn 318
Add to Calendar 2024-09-18T13:30:00 2024-09-18T15:30:00 Electrodynamics of Non-topological Solitons Event Information: In this thesis, we study a class of non-topological solitons known as "Q-balls" which arise in complex scalar field theories with U(1) symmetry. We focus on the case where the U(1) symmetry is gauged and the theory admits a coupling to electromagnetism; the corresponding solitons are known as "gauged Q-balls". Using numerical simulations, we examine the dynamical behaviour of these objects in various scenarios. First, we investigate the classical stability of gauged Q-balls under assumptions of axial symmetry. Considering two different forms for the scalar field potential, we find evidence for gauged Q-ball configurations which remain stable with respect to axisymmetric perturbations of the fields. We also find evidence for unstable configurations which are quickly destroyed in response to the perturbations (for example, through dispersal of the fields or via fragmentation into smaller structures). Next, we investigate head-on collisions of gauged Q-balls at relativistic velocities. We test the effects of the electromagnetic coupling strength, initial velocity, relative phase, and relative charge of the colliding binary on the outcome of the collision. Depending on the values of these parameters, we observe a variety of distinct phenomena such as gauged Q-ball mergers, fragmentation, charge transfer, charge annihilation, Q-ring formation, and electromagnetic radiation production. Finally, we investigate the dynamics of gauged Q-balls using fully three-dimensional numerical simulations. Extending the previous analyses, we find evidence for configurations which remain classically stable against generic perturbations in three spatial dimensions. We also consider off-axis collisions of gauged Q-balls and find that the impact parameter can play a significant role in determining the outcome of the collision. Together, these results address several key questions about the dynamics of non-topological solitons in general and the stability of gauged Q-balls in particular. Event Location: Henn 318

Predictive Metrics for Moist Desquamation in Treatment Planning for Breast Radiotherapy

Event Time: Wednesday, September 25, 2024 | 12:00 pm - 2:00 pm
Event Location:
Zoom https://ubc.zoom.us/j/69727529419?pwd=8tzHM4QhGjNpV26SgpqRhuEfAqLfyb.1

Meeting ID: 697 2752 9419
Passcode: 501860
Add to Calendar 2024-09-25T12:00:00 2024-09-25T14:00:00 Predictive Metrics for Moist Desquamation in Treatment Planning for Breast Radiotherapy Event Information: Abstract: The objective of this thesis was to establish techniques for predicting and modelling moist desquamation (MD). The work in this thesis is based on the clinical studies of the novel Carbon Fibre Adjustable Reusable Accessory (CARA) breast support device. The epidermal dose measurements, treatment plans, and skin assessments from clinical studies of the CARA device were used to develop models to be applied during treatment planning to reduce the occurrence of MD in breast radiotherapy. In the first study of this thesis, in vivo film dosimetry was used to establish a relationship between the epidermal surface area receiving various levels of radiation dose and the corresponding skin reactions.  The results of this study indicated potential dose-area based constraints on the skin for use during treatment planning. For the second study, the in vivo film dosimetry was compared against the Eclipse(Varian Medical Systems) treatment planning system’s Analytical Anisotropic Algorithm (AAA) and AcurosXB (AXB) dose calculation algorithms. This study produced recommendations for skin rind definitions for the two dose calculation algorithms to improve consistency in epidermal dose reporting. In the final study, a metric was developed to predict MD based on the spatial distribution of dose across the skin. This metric maps the risk of MD across the skin’s surface based on the treatment planning system’s skin dose calculations. The predictive model was validated against a second dataset, and showed promise in its performance. Event Location: Zoom https://ubc.zoom.us/j/69727529419?pwd=8tzHM4QhGjNpV26SgpqRhuEfAqLfyb.1 Meeting ID: 697 2752 9419 Passcode: 501860