WITP Summer Student Symposium 2022
17 Aug 2021, UWinnipeg & Online
Pulsar Wind Nebulae: Powerful Cosmic Ray Accelerators
When a massive star explodes in a supernova, it often leaves behind a rapidly spinning compact neutron star. Young, energetic neutron stars generate strong relativistic winds, which as they interact with the surrounding medium, create a pulsar wind nebula (PWN) that can shine across the electromagnetic spectrum. PWNe make the largest population of gamma-ray sources in our galaxy and are strong candidates for acceleration of cosmic rays to PeV energies (pevatrons). In collaboration with Columbia University researchers, we are analyzing PWNe in multiple wavelengths to form a more complete understanding of these extreme sources. In this presentation, we highlight our research targeting the PWN G309.92-2.51 making use of NASA's NuSTAR satellite sensitive to the high-energy x-ray band.
Estimation of Spin of the Galactic Black Hole Candidate GRS 1758-258 though X-ray Spectroscopy
We present the results X-ray spectral study of the persistent Galactic black hole X-ray binary GRS 1758-258. The data was observed simultaneously by Swift and NuSTAR. Our spectral model fitting with an absorbed power-law model revealed a broad Fe line and reflection hump in the spectrum. We applied numerous flavours of the relativistic reflection model for the spectral analysis. We cover the basic accretion geometries for the models and provide brief introduction to each of them. The spectral models suggests the spin of the black hole is > 0.92. The source was in the low/hard state during the observation, with the hot electron temperature of the corona estimated to be kTe ~ 140 keV. The black hole is found to be accreting at ~ 1.5% of the Eddington limit during the observation, assuming the black hole mass of 10 solar mass and distance of 8 kpc. (collaborators: Argha Jit Jana, Samar Safi-Harb, H K Chang, S Naik)
Long-term NICER Monitoring of Black Hole Low-mass X-ray Binary 4U 1755-338
Black Hole Low-mass X-ray Binaries (BH LMXBs) are among the most important laboratories to study the extreme physics in the presence of a deep gravitational well. They give rise to several important phenomena observable primarily in the X-ray, namely Quasi-Periodic Oscillations (QPOs) in X-ray flux and time-lags between energy bands. Using two years of archival data from the Neutron Star Interior Composition Explorer (NICER) we've been performing a comprehensive investigation of the source 4U 1755-338 which began outbursting in April, 2020 after a 24-year period of quiescence. We thus far report the discovery of two probable Low Frequency QPOs around ~0.1 Hz alongside a persistently soft spectral state. Future work will include studying time/reverberation lags in greater detail, numerical simulations to reproduce observational data of interest, and potential direct mass measurements with collaborative observations in the optical.
Phase Diagram of Reheating and Axion Inflation
Reheating at the end of inflation provides an excellent backdrop to study early universe particle production. The physics of reheating is still very much an open question in physics research. My research looks at the physics at the end of inflation using Floquet analysis. Floquet analysis allows us to see how the axion field is coupled to itself and the gauge field at the end of inflation. It also allows us to look at energy densities at the end of inflation, corresponding to particle production in the early universe. This coupling allows us to create a phase diagram of the energy densities to see which parameters allow for particle production in the early universe for self resonance and gauge production.
Investigating Plasma Lensing Structures by Simulating the Propagation of Radio Wavefronts
We simulate the propagation of radio wavefronts through spatially varying continuous media to gain insight into the nature and structure of plasma lenses thought to produce extreme scattering events (ESEs). By first ray-tracing through spatially varying media, we then construct the propagation of wavefronts. We form a mapping between the source and the image to produce intensity maps. With this approach, we have produced the resulting light curves through turbulence generated by Fourier methods, as well as turbulence generated using PythonMHD, an MHD simulation code developed by Delica Leboe-McGowan at the University of Manitoba. Future explorations of wavefront propagation through plasma structures of various dimensionality such as spheres, cylinders, and sheets are planned.
Fermion propagator in presence of a strong external magnetic field
A possibility of generation of an extremely strong magnetic field in the ultra-relativistic heavy ion collision experiments at RHIC and LHC, has encouraged the research interest in the magnetic modifications of the quark gluon plasma properties. On the theoretical side, the perturbative approach for the extraction of thermodynamic properties, dispersion properties etc. requires the evaluation of the Feynman loop diagrams. Thus, as a starting point of such diagrammatic calculation in the presence of an external magnetic field, one has to incorporate the magnetic field modifications in the propagators. In this talk, the origin of such magnetic modification in the fermion propagator and its consequences in the gluon dispersion will be addressed.
The Neutron Star Merger: GW170817
GW170817 is the first and only event to-date to be observed in both gravitational and electromagnetic waves (from radio to high-energy photons). This new multi-messenger event, discovered on Aug 17 (2017), has generated a lot of interest among the astrophysics community worldwide, and is an important milestone in astrophysical research. In addition, while we know that this event resulted from two neutron stars merging, the final mass of GW170817 puts it in the stellar graveyard; that is to say, a mass region in between a neutron star and a black hole where we observe almost no objects, but theory states such objects should exist. This research is aimed at understanding the aftermath of this neutron star merger by examining Chandra X-ray and multi-wavelength/multi-messenger observations. We are particularly interested in testing the GW170817 evolution against a kilonova remnant model, in preparation for the next LIGO phase of observations.
Entanglement in topological insulators
Explaining a complex topic such as "entanglement in topological insulators" is extremely difficult, even when the audience has relative expertise in the topic. In my presentation, I will try to build on a topic that students already know. That is; a particle in a box. I will use the "particle in a box" concept to separately discuss topology, insulating materials and entanglement. At the end, I will try to bring them all together to understand my project.
Early Time Dynamics in Heavy Ion Collisions
When a particle accelerator is used to make a high energy collision between two heavy nuclei, a plasma is formed. This plasma can be analyzed to examine the behaviour of quarks and gluons. We do this by calculating the electric and magnetic fields surrounding the plasma. These fields are analyzed to produce an approximation using a technique called expanding in proper time. This analysis yields very large equations. As we attempt to solve these equations at times increasingly further away from the time of collision, computations slow down so much that the process becomes unviable with existing methods. Our work focuses on developing computational methods to speed up the analysis. Specifically, we are focusing on the use of the Julia programming language to make the computation feasible.
Continuation of Bryce Friesen's talk topic
State transfer on weighted graphs with twin vertices
Twin vertices in a graph are vertices with the same neighbourhood. In this talk, we examine the types of state transfer exhibited by graphs with twin vertices.
Rodrigo Alves Pimenta
Free fermionic and parafermionic quantum spin chains
We will discuss a new family of quantum spin chains with multispin interactions whose spectrum has a free fermionic or parafermionic nature. Despite the free nature of the spectrum, these spin chains in general cannot be solved by the Jordan-Wigner transformation. However, exploiting integrability, it can be shown that the quasi-energies are related to the roots of certain characteristic polynomials given by higher-order recurrence relations. In particular, the so-called Laguerre bound for the largest root of the characteristic polynomial allows a very efficient computation of the mass gap, providing a relevant tool for the study of critical quantum chains with and without quenched disorder. Beyond the spectral level, many interesting aspects of the Hamiltonians remain to be understood, for example, the computation of correlation functions and entanglement entropy.
Completely Dark Dark Matter & the de Sitter Swampland Conjecture