PHYS PHEST 2023

Phys Phest is a celebration of the research being conducted in the Physics Department by our graduate students who have completed (approximately) their first year. 
 
Please come out to support and vote for best talks!!!
 
Afterwards, prizes for best talks at Phys Phest will be presented at the Corn Roast at Riverside Park. 
 
Pizza lunch will start at 12:00 with talks to follow.

Schedule

Abstracts

Exploring Computational Physics Exercises as a Tool for Learning Physics

Victoria Arbour, MSc Candidate
Advisor: Michael Massa

Over the past decade, there has been a growing recognition in the physics community of the need for students in undergraduate physics programs to develop computational skills. Computational skills are used in a variety of careers and teach students transferrable skills such as problem-solving, analysis, and critical thinking. While the value of these skills is generally acknowledged, integrating coding activities into physics courses begs the question: How does engagement with computational activities enhance students’ learning of physics? This research project seeks to investigate the benefits and challenges of using computational exercises to learn content delivered in undergraduate physics courses. In a second-year electricity and magnetism course, students wrote Python code to numerically compute vector derivatives for various fields presented either visually or symbolically. Learning gains were investigated using pre- and post-quizzes. Additionally, interviews were conducted with students as they developed their code. These provided insights into their thought process, confidence in their code, and reconciliation of the computed results with their pre-conceptions of the divergence and curl of the vector fields explored.

Finding Stability in Interaction: a study on self-gravitating, anisotropic fluid spheres

Joshua (Tom) Cadogan, MSc Candidate
Advisor: Eric Poisson

The study of compact objects, such as neutron stars, black holes, and other exotic theoretical bodies in general relativity has been a growing field in recent decades. As experimental probes for these extreme systems are developed, the associated theory must also be refined to uncover the underlying physics. A prime example of this is the yet-poorly understood general relativistic fluid mechanics of anisotropic (directional) fluids; a formalism which could describe everything from viscosity within accretion disks to the structure of exotic stars.

Here, we present the problems with the current literature of anisotropic fluids and develop a “fluid first approach” by borrowing from the fluid dynamics of liquid crystals. This theory is then extended to the application of a two-phase stellar model in Newtonian gravity, the structural and observational properties of which are presented.

An Exploration of the r-process in Neutron Star Mergers

Stephanie Ciccone, MSc Candidate
Advisor: Liliana Caballero

Neutron star mergers are an ideal energetic environment for rapid neutron captures to take place that lead to the production of neutron-rich nuclei far from the elemental valley of stability. This r-process neutron capture regime is explored through the testing of various mass models and astrophysical conditions in the simulation code PRISM, with current progress and results discussed here. This allows us to gain a better understanding about the production of elemental abundances in the universe.

Equation of State, Neutron Star Mergers and Neutrinos

Paul Deguire, MSc Candidate
Advisor: Liliana Caballero

Neutron stars are very dense objects that result from the death of a main-sequence star with an original mass between 8 and 25 solar masses. Studying the interior of these stars through events such as binary neutron star mergers can help explain the behavior of ultra-compact matter similar to that found inside an atomic nucleus. During these mergers, gravitational energy transfers to neutrinos which escape the stellar matter, carrying information about the equation of state of neutron stars with them. To test our understanding of nuclear matter in extreme conditions, we can compare neutrino yields detected in neutrino observatories on Earth to theoretical yields. Theoretical yields are calculated using binary neutron star merger simulations with different ultra-compact matter equations of state to account for the number of neutrinos produced during a merger. The three different equations of state used are SFHo, DD2, and NL3. This study sets out to determine if the equation of state of ultra-compact matter impacts the cosmic neutrino background, and, if so, if detection of this effect is possible in neutrino observatories. We found that the SFHo equation of state results in a significantly higher number of neutrinos emitted during the merger when compared to other equations of state.

Love Numbers and the Multipole Moments of Static Binary Systems

Victoria Leaker, MSc Candidate
Advisor: Eric Poisson

Knowledge of the internal composition of neutron stars is limited by a poor understanding of how extremely high densities impact the properites of nuclear matter. It is impossible to produce such densities in a lab environment, bringing about the need for new theoretical models to study such systems.

The tidal deformation of compact bodies such as neutron stars or black holes has been shown to play an important role in the emission of gravitational waves during a binary inspiral and convey important information regarding a body’s internal composition and structure. To measure the tidal deformability of a compact object, the Love numbers kl are primarly used. They depend on the equation of state for a neutron star and vanish for black holes.

In a recent paper it was proved that the the tidally induced multipole mo- ments of a black hole do indeed vanish. While the approach used was able to verify the usual relation between Love numbers and tidally induced multipole moments for black holes, it has yet to be applied to other compact bodies such as neutron stars. By adding a small charge to a neutron star and calculating the multipole moments using a similar formulation to what was used for black holes, the arguments used can be further validated. If the obtained results are comparable to the known expressions for multipole moments and Love numbers, then the formulation can indeed be considered correct allowing for further study of the internal constitution of compact stellar bodies.

The proposed resolution relies on the partitioning of the system into interior and exterior zones, requiring the respective solutions to be matched at the adjoining boundary. As was the case for a black hole, the tidal environment is produced by a charged particle of mass m and charge q placed in the vicinity of the material body with the gravitational and electrostatic forces considered once again to be equal and opposite in magnitude and direction.

Unrestricted Hartree-Fock, and the ground state of the 2D Hubbard model below half-filling

Robert Leslie, MSc Candidate
Advisor: Alexandros Gezerlis

Hartree-Fock is a commonly used numerical technique to study a variety of Quantum Mechanical many body systems. One of its applications is to study the ground state of the Hubbard model, which can approximate the behaviour of fermions in a 2D lattice at low temperature. By using a self-consistent scheme for unrestricted Hartree-Fock, it can be shown that the ground state of the Hubbard model exhibits Anti-Ferromagnetic order which can be used to simulate the same kind of Anti-Ferromagnetic behaviour in transition metal compounds at sufficiently low temperature. If we increase the hole density (doping parameter) then we will begin to see a state that is of AFM order, but with dynamic behaviour. If our lattice size is large enough to supress finite-size effects, then we will begin to see charge density waves, as well as staggered spin density waves, where the wavelength is inversely related to the doping parameter. It can also be shown that by varying the interaction temperature ratio (U/t) that these waves can begin to exhibit non-sinusoidal behavior, as well as change their orientation. The order in which these transitions occur is dependent on the doping parameter h. By employing a number of numerical techniques, we can map out the phase diagram for the AFM region of the Hubbard model, as well as the AFM phase boundaries

Computing the dynamic Love numbers of neutron stars in general relativity

Tristan Pitre, MSc Candidate
Advisor: Eric Poisson

Neutron stars are host to some of the most extreme conditions in the Universe, making them extraordinary laboratories. Their internal properties are related through the equation of state, which uses the star’s microscopic properties to provide information about the macroscopic properties. Unfortunately, the equation of state of neutron stars is still unknown. Multiple methods have been used to try to constrain their equation of state, but none have been definitive. A newer interesting method is to study the neutron star's deformation by a companion in a binary system through gravitational waves. This deformation is described by Love numbers, which are specific to the star. Love numbers are also imprinted by the interior properties of the object, meaning that their measurement relates information about the star’s equation of state. In this project, we mainly focus on dynamic Love numbers. They correspond to the dynamic response of the star to its companion’s gravitational field. They haven’t been studied a lot and the methods used to compute them in general relativity have been too complicated and based off of crude approximations. We provide an easier and more complete way to compute them.

Observational features in a beyond-Kerr spacetime: Central object's critical curve, and Gravitational wave phase difference

Hassan Khalvati, PhD Candidate
Advisor: Huan Yang

Recently, we computed the metric of a vacuum stationary axisymmetric spacetime using Ernst formalism. The metric contains a generic non-Kerr deviation in the quadrupole moment and is accurate up to very high order in the inverse radial distance. Using such a metric, we have tried to study any potential observational feature of such a beyond-Kerr spacetime. We have studied the deviation in the observable size of the central object by numerical ray-tracing approach and compared the deviation with the critical curve for the Kerr black hole photon sphere. We also concluded that there is a degeneracy in simulating the shape of the central object in the parameter space between spin and the deviation in quadrupole moments of the central object.
In addition, we tried to study an EMRI (Extreme Mass Ratio Inspiral) system considering this modified spacetime as the background and calculated the phase difference between the gravitational radiation from this system with respect to the Kerr background.

In the end, we have shown that both of these observational features are potentially detectable by future space-based black hole detectors and gravitational wave detectors.

Probing Electrocatalysts for the Hydrogen Economy: X-ray Absorption Spectroscopy Insights

Cameron McGuire, PhD Candidate
Advisors: De-Tong Jiang, Aicheng Chen

In an era marked by growing environmental consciousness and the need to shift away from fossil fuels, electrocatalysts emerge as pivotal players in the pursuit of sustainable energy solutions. The hydrogen economy holds promise as a clean and energy-dense alternative. However, the widespread adoption of hydrogen-based technologies, for both storage and creation, requires cost-effective and efficient electrocatalysts, which often pose challenges due to their dependence on rare and expensive elements.

To address this challenge, research endeavours are increasingly focused on dispersing these rare materials as nanoparticles on various conductive substrates. Yet not all synthesis methods yield equally effective results. Therefore, a critical aspect of advancing these systems is the thorough characterization of electrocatalysts at the atomic and molecular levels.

In this presentation, we delve into the application of X-ray absorption spectroscopy to characterize three distinct electrocatalysts poised to shape the hydrogen economy: palladium on graphene for hydrogen storage, ruthenium on graphene for hydrogen evolution, and cobalt hydroxide on an alkali-treated titanium dioxide substrate, exhibiting single-atom behaviour for hydrogen evolution. Join us as we explore the intricacies of these systems, shedding light on their potential to drive the future of sustainable energy.

Effective Field Theory Truncation Error

Habib Yousefi Dezdarani, PhD Candidate
Advisor: Alexandros Gezerlis

Effective field theories allow us to study the physics of systems with a different scale, which is now common in physics. The application of EFT methods to nuclear systems provides the opportunity to estimate the uncertainties coming from the nuclear Hamiltonian. Realistic predictions of nuclear observables require accurate many-body methods and reliable nuclear Hamiltonians with quantified theoretical uncertainties. Nuclear Hamiltonian suffer from three major sources of uncertainties:

1. The truncation of the chiral expansion, which results in a description of the physical with an insufficient operator basic.
2. The related uncertainty of LECs, which additionally originates from fits to a poor database or fits to nonideal systems.
3. The dependence of the regularization scheme and scale.

In this presentation, I will be talking about errors coming from EFT as well as their effect on physical observations.