Winnipeg Institute
for Theoretical Physics

WITP

WITP Summer Student Symposium 2019
28 Aug 2019, Room 3M69, Manitoba Hall, University of Winnipeg

Abstracts

Bassel Alkadour
A simulation study of intra-and inter-particle magnetism in triangular arrays of maghemite nanoparticles
A study of maghemite nanoparticles on a two dimensional triangular array was carried out using a sLLG approach. Results for simple dipoles show the expected phase transition to a ferromagnetic state at a finite temperature but with a ground state exhibiting a continuous degeneracy that was lifted by an order-from-disorder mechanism at infinitesimal temperatures. The nanoparticle array consisted of 7.5~nm diameter maghemite spheres with bulk-like superexchange interactions between Fe-ions in the core, and weaker exchange between surface Fe-ions and a radial anisotropy. We find that the vacancies on the octahedral sites in the nanoparticles combine with the surface anisotropy to produce an effective random temperature-dependent anisotropy for each particle[1]. This leads to a reduction in the net magnetization of the nanoparticle array at zero temperature compared to the simple dipole array[2]. The spin-wave analysis shows that this effect increases the spin-wave frequency and introduces a low-frequency peak due to spin-glass-like relaxation processes.
[1] B. Alkadour, J. I. Mercer, J. P. Whitehead, J. van Lierop, and B. W. Southern, Phys. Rev. B 93, 140411 (2016).
[2] B. Alkadour, B. W. Southern, J. P. Whitehead, and J. van Lierop, arXiv e-prints , arXiv:1904.05515 (2019).

Cole Coughlin
A Game of Galactic Hide and Seek: Galactic Interactions Obscure Active Black Holes
This talk will focus on how galactic interactions obscure the broad-line region of active galactic nuclei, as well as the algorithm used to find these galactic interactions. This talk will also explain how the findings of this research fit in with the current model of active galactic nuclei and their unification.

Brad Cownden
A Perturbative Theory for Periodically Driven Scalars in Global AdS
The evolution of scalar fields on asymptotically AdSd+1 backgrounds has been extensively studied both within the framework of the AdS/CFT correspondence as well as within general stability considerations of maximally-symmetric solutions to Einstein’s equations. The negative curvature of AdS ensures that perturbations of minimally-coupled scalar fields can return to the origin in finite time, whereupon the infalling field can be gravitationally focused before traveling outwards again. Gravitational collapse may seem like the only possible future for such a system; however, for small amplitudes there are initial data that remain stable over multiple refocusing events.
In this talk, we discuss ongoing work into the perturbative evolution of a minimally-coupled scalar field in asymptotic AdS, subject to periodic boundary conditions. This scenario is often described as “pumped” due to the regular injection of energy through the boundary. Using established time averaging methods, we derive equations for the slowly- varying amplitudes of the eigenmodes so that the cascade of energy to short length scales is balanced by inverse energy transfer. These solutions then resist collapse over perturbative time scales. The introduction of non-zero boundary terms requires considering an additional type of scalar field solution: non-normalizable eigenmodes. We further examine the effects of including several types of non-normalizable solutions, and derive evolution equations for the normalizable eigenmodes in this pumped system. Finally, we numerically investigate if any of these field configurations are naturally vanishing, as is observed when only normalizable eigenmodes are considered.

Neil Doerksen & Austin MacMaster
Neutron Star Collision in X-ray Vision
What is happening at the centre of neutron star merger GW170817? Neil and Austin present their summer's research on the first and only event observed, so far, in both electromagnetic and gravitational wave radiation.

Sofiya Makar
Non-perturbative scalar theories: convergence of the thermodynamic pressure
We calculate the thermodynamic pressure in a toy model in which all particles are treated as spinless scalars. The nPI method is used to do calculations non-perturbatively. A renormalization group approach is used to handle divergences. The goal of the project is to compare results at the 2,3,4 and 5 loop orders in the effective action.

Brett Meggison
Using 3-D QED to describe Anisotropic Graphene

Paul Mikula
Non-equilibrium approach to holographic superconductors using gradient flow
We study a charged scalar field in a bulk 3+1-dimensional anti-de Sitter (AdS) spacetime with a planar black hole background metric. Through the AdS/CFT correspondence this is equivalent to a strongly coupled field theory in 2+1 dimensions describing a superconductor. We use the gradient flow method and solve the flow equations numerically between two fixed points: a vacuum solution and a hairy black hole solution. We study the corresponding flow on the boundary between a normal metal phase and a superconducting phase. We show how the gradient flow moves fields between two fixed points in a way that minimizes the free energy of the system. At the fixed points of the flow the AdS/CFT correspondence provides an equivalence between the Euclidean on-shell action in the bulk and the free energy of the boundary, but it does not tell us about fields away from equilibrium. However, we can formally link static off-shell configurations in the bulk and in the boundary at the same point along the flow. For quasistatic evolution at least, it may be reasonable to think of this link as an extension of the AdS/CFT correspondence.

Kyle Monkman
Entanglement and Topology of Multileg Su-Schrieffer-Heeger Chains
The use of topological concepts in physics is a popular research topic for physicists in the world today. One of the broad promises of topology in physics is useful applications of quantum mechanics such as quantum computing. In our work, we study the topology and the entanglement of coupled Su-Schrieffer-Heeger chains. Using the topological invariants and looking at the protected edge states, we find that the coupled chains exhibit a rich topological phase diagram. We look at various measures of many-body entanglement to understand how the edge states could be used to generate long range entanglement experiments.

Michael Ramsay
Building Tools for Supernova Remnant Research
Supernova remnants (SNRs) are the remains of dying stars that explode in dramatic supernova explosions. Researchers use them for studying Galactic dynamics and evolution, and as natural laboratories for exotic, high energy phenomena. SNRcat is an online website developed at the University of Manitoba cataloguing SNRs and their properties, and is used worldwide by SNR researchers. This talk highlights the new version of SNRcat and on-going additions, which include imagery of every known Galactic SNR, with relevant source catalogues overlaid on the images, and interactive spatial plots of the remnants.

Mainak Singha
First Systematic Characterization of AGN driven ionized outflows
The broad line wings in the optical [OIII] 5007 emission line are one of the best signatures of fast ionized gas outflows on host galaxy scales in AGN. While large spectroscopic surveys like SDSS have characterized the kinematics of [OIII] for large samples of AGN in detail, they cannot determine the location and energetics of those outflows. As part of the Close AGN Reference Survey (CARS) we obtained spatially-resolved IFU spectroscopy for a representative sample of 40 luminous type 1 AGN at 0.01

Cole Treyturik
Using Nucleosynthesis to Unveil the Origins of Supernova Remnants
Supernova remnants are ever-expanding clouds of gas and dust whose very nature is defined by the supernova that created them, reflecting the diverse nature of their stellar progenitors, their supernova forebears, and the many different environments in which they occur. The study of these supernova remnants thus allows us to infer much information about not only supernova explosions, but also about late-stage stellar evolution, granting us greater insight into these realms. An important mechanism through which we are able to study these supernova remnants is the process known as supernova nucleosynthesis. Within the brief moments of a supernova, many elements are created, some of which cannot be formed within the normal lifetime of a star. The types of the elements – and the abundances thereof – are determined primarily by the attributes of the supernova remnant’s stellar progenitor. By observing the supernova remnant, obtaining the abundances of these elements within, and comparing to models of supernova nucleosynthesis, we are able to determine much about the nature of the supernova that created it.

Andrew Urichuk
Transport properties of integrable systems
Cold atom systems in 1-dimension are well modelled by a class of exactly solvable models that do not thermalize in the usual sense. I will introduce several exotic transport phenomenon realized in these systems, with a special focus on their non-decaying currents and DC spin-conductance that exhibits a fractal dependence on the anisotropy between the X-Y and Z axes.