Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session D17: Undergraduate Research IILive Undergrad Friendly
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Sponsoring Units: SPS Chair: Brad Conrad, SPS |
Saturday, April 17, 2021 1:30PM - 1:42PM Live |
D17.00001: Modeling AGN Accretion-Disk Winds Mary Ogborn, Keigo Fukumura Type 1 Seyfert galaxies are bright sources of ultraviolet light and X-Rays that also host active galactic nuclei (AGNs). Outflows can be observed from these galaxies and are thought to be produced from the accretion disk around the AGN due to the presence of a global magnetic field. These ionized outflows show as X-Ray warm absorbers, which allows analysis of the X-Ray spectrum to learn more about the structure of these outflows, as well as the AGN itself. In the context of magnetohydrodynamics (MHD), we utilize a magnetically-driven disk-wind model where accreting plasma is magnetically launched and accelerated by the action of a global magnetic field around supermassive black holes in AGNs. Being coupled to photoionization calculations with XSTAR code, we have constructed a grid of absorption spectra, which can then be convolved with a continuum spectral component to easily facilitate spectral analysis with XSPEC package. As part of our ongoing investigations in spectral modeling of X-ray warm absorbers, we have applied the wind model to 3 exemplary Seyfert 1 AGNs (NGC 3783, MCG-6-30-15 and NGC 3516) in an effort to constrain the strength of the observed winds using multi-epoch Chandra X-Ray Observatory’s High Energy Transmission Grating Spectrometer (HETGS) data. [Preview Abstract] |
Saturday, April 17, 2021 1:42PM - 1:54PM Live |
D17.00002: Simulation of Light Emitted from a Test Mass Orbiting an Extreme Black Hole Benjamin Brown One of the most famous results from Einstein’s theory of general relativity is the bending of light by massive objects. In this undergraduate thesis, we seek to simulate what a distant observer would see from a luminous object orbiting a black hole. To do this, we have developed a general program which calculates null geodesics emitted from a test mass orbiting a central mass, taking relativistic beaming into account. We will show results for the cases of Schwarzschild, Reissner-Nordstrom, and Kerr black holes with an emphasis on black holes that have extreme charge-mass and angular momentum-mass ratios. [Preview Abstract] |
Saturday, April 17, 2021 1:54PM - 2:06PM Live |
D17.00003: Impact of the Pre-Supernova Stellar Compactness in Gravitational-Wave Populations Maciej Dabrowny, Davide Gerosa, Nicola Giacobbo Detections of gravitational waves have revolutionized the understanding of black-hole binaries and double neutron stars, as well as their coalescence. These detections have provided a new way to test our best predictions for the evolution of binary stars which ultimately merge as black-hole or neutron-star binaries. However, the evolution of compact-object binaries is still riddled with enigmas such as the effect of different supernova-explosion prescriptions. Specifically, modern supernova models predict that the outcome of the explosion is set by the compactness (not just the mass!) of the stellar core. We present the first implementation of such advances in the state-of-the-art population-synthesis code MOBSE. We test how different possible physics of the supernova mechanisms impact the key gravitational-wave observables. How does the core-collapse explosion mechanism affect the resulting remnant? How does the pre-supernova compactness affect the mass spectrum of gravitational-wave sources? [Preview Abstract] |
Saturday, April 17, 2021 2:06PM - 2:18PM Live |
D17.00004: Constraining scalar-tensor theories of gravity using neutron star mass-radius relationship observations Semih Tuna, Fethi Mubin Ramazanoglu, Kivanc Ibrahim Unluturk We use the mass-radius measurements of neutron stars to constrain the parameters of the spontaneous scalarization scenario in scalar-tensor theories. We first calculate the mass-radius relationship of neutron stars numerically for given parameter values of $\beta$ and scalar mass $m_\phi$ using the recently introduced relaxation method of Rosca-Mead et al. Subsequently, we employ Bayesian statistics to construct a probability distribution on the $\beta-m_\phi$ space. It is not possible to conclude whether scalar-tensor theories are preferred to general relativity using this data due to our lack of knowledge of the equation of state of nuclear matter, but we can rule out values of $\beta < -20$. Such high values of $\beta$ are possible due to the exponential decay of the scalar field away from the star due to the mass term, hence our results provide the best known observational limits to $\beta$. [Preview Abstract] |
Saturday, April 17, 2021 2:18PM - 2:30PM Live |
D17.00005: Progress on Novel Tests of Gravity at the Submillimeter Scale Alyssa Johnson, Kyle Galaz, Michael Gengo, Emily Ord, Frank Trombetta, Kassandra Weber, C.D. Hoyle The unification of the Standard Model and General Relativity may result in the failure of the Weak Equivalence Principle (WEP) and/or the gravitational Inverse-Square Law (ISL). Our fundamental understanding of gravity is questioned by these incongruities. However gravity is not well tested below the millimeter scale. Undergraduate researchers and faculty at Humboldt State University are using an experiment to measure gravitational interactions below 50 microns. The experiment uses a torsion pendulum with equal masses of two different materials arranged as a composition dipole. The twist of the torsion pendulum is measured as an attractor mass in a parallel-plate configuration is oscillated nearby. This oscillation creates a time dependent torque on the pendulum. The magnitude and size of this torque may be studied lead to test for deviations in the WEP or ISL at this untested scale. This talk will focus on the mitigation of the variations in the apparatus' inclination by use of an active leveling scheme that utilizes data from a tilt sensor that is fed to a PID loop. [Preview Abstract] |
Saturday, April 17, 2021 2:30PM - 2:42PM Live |
D17.00006: Singularities in Semiclassical Cosmology Joseph Nyhan, Eleni-Alexandra Kontou, Daniel Siemssen The semi-classical Einstein equation (SEE) is an attempt to rectify the classical nature of Einstein’s field equations in our quantum universe: the matter portion of Einstein’s equation, the energy-momentum tensor, is quantized. This project analyzes which conditions today lead to a primordial singularity in the past within our universe in the context of the SEE. We use derived solutions of the SEE for a scalar field in an FLRW universe for our analysis. In this context, we define a singularity occurrence to be when the scale factor within the FLRW metric goes to zero. The investigation of the existence of singularities was performed by varying the initial conditions of a variety of parameters, checking simpler, bounding differential equations, and using analytical and numerical methods. [Preview Abstract] |
Saturday, April 17, 2021 2:42PM - 2:54PM Live |
D17.00007: Dimensional Crossover In Non-Relativistic Effective Field Theory II Murtaza Jafry, Silas Beane Isotropic scattering in various spatial dimensions is considered for arbitrary finite- range potentials using non-relativistic effective field theory. With periodic boundary condi- tions, compactifications from a box to a plane and to a wire, and from a plane to a wire, are considered by matching S-matrix elements. The problem is greatly simplified by regulating the ultraviolet divergences using dimensional regularization with minimal subtraction. Gen- eral relations among (all) effective-range parameters in the various dimensions are derived, and the dependence of bound states on changing dimensionality are considered. Generally, it is found that compactification binds the two-body system, even if the uncompactified system is unbound. For instance, compactification from a box to a plane gives rise to a bound state with binding momentum given by $ln ( \frac{1}{3} + √5 )$ in units of the inverse compactification 2 length. This binding momentum is universal in the sense that it does not depend on the two-body interaction in the box. When the two-body system in the box is at unitarity, the S- matrices of the compactified two-body system on the plane and on the wire are given exactly as universal functions of the compactification length. [Preview Abstract] |
Saturday, April 17, 2021 2:54PM - 3:06PM Live |
D17.00008: Searching for Lorentz and CPT violation using charge-to-mass ratio comparisons in Penning traps Mohammad Farhan Rawnak, Yunhua Ding Lorentz and CPT symmetries are the fundamental symmetries of our current best theories describing nature- General Theory of Relativity and the Standard Model of Particle Physics. Many theories such as string theory and quantum loop gravity suggest that tiny violations of Lorentz and CPT symmetries could emerge naturally via spontaneous symmetry breaking. Studying these symmetry-violating signals is of great importance because it could give birth to new physics beyond the Standard Model. One way to test these symmetries is to compare the fundamental properties of a particle to those of its antiparticle. In our work, we explore the theoretical and experimental prospect for Lorentz and CPT violation using charge-to-mass ratio comparisons from penning trap experiments. We first derive the leading order contributions due to Lorentz and CPT violation to the cyclotron frequencies of a confined particle and antiparticle and then relate them with the experimental charge-to-mass ratios comparisons. By identifying the relations between the comparisons and coefficients for Lorentz and CPT violation, we obtain first-time constraints on 69 coefficients for Lorentz and CPT violation from published Penning-trap results. [Preview Abstract] |
Saturday, April 17, 2021 3:06PM - 3:18PM Live |
D17.00009: Magneto-Ionization Spacecraft Shield For Interplanetary Travel(MISSFIT): General Overview Molly McCord, David Atri, Justin Brutger, Keegan Finger, Luke Hofmann, Trace Johnson, Timothy Kutnink, Julie LaFranzo, Meredith Luttrell, Lorien MacEnulty, Gavin Menning, Ethan Morton, Noah Peterson, Athanasios Petridis, Ajal RC, Will Thomas, Daniel Viscarra One issue concerning manned interplanetary travel is intense radiation exposure from solar wind and cosmic rays. The purpose of this collaboration is to develop a conceptual design for a magneto-ionization shield for radiation and a technique to create artificial gravity. One aspect of the conceptual design is the development of a magnetic field that will deflect high energy charged particles and trap lower energy particles in regions of space where those particles will lose energy through scattering, taking inspiration from the Earth's ionosphere and magnetic field. A concern of the group is debris collisions because of the large gas-containing chambers that aide in shielding. Materials are being investigated for their mechanical response to collisions with small particles and their passive radiation absorption properties. These materials include Demron, Nitinol, Carbon-fiber, and other materials. This interdisciplinary collaboration is a student-led project involving students of all academic years that meets weekly to exchange information and discuss progress. This project is supported by the Iowa Space Grant Consortium under NASA Award No. 80NSSC20M0107. [Preview Abstract] |
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