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 Cole Treyturik Andrew Urichuk
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
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.
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.