Bulletin of the American Physical Society
Far West Section Fall 2022 Meeting
Volume 67, Number 10
Friday–Saturday, October 7–8, 2022; University of Hawaiʻi at Mānoa, Honolulu, HI
Session G03: Gravitation and Cosmology |
Hide Abstracts |
Chair: Veronica Bindi, University of Hawaii at Manoa Room: University of Hawai'i at Manoa, East-West Center Pacific |
Friday, October 7, 2022 1:45PM - 1:57PM |
G03.00001: Comments on the cosmological constant in generalized uncertainty models Douglas A Singleton, Peter Martin, Michael Bishop, Joey Contreras The existence of a small, non-zero cosmological constant is one of the major puzzles in fundamental physics. Naively, quantum field theory arguments would imply a cosmological constant which is up to 10$^{120}$ times larger than the observed one. It is believed a comprehensive theory of quantum gravity would resolve this enormous mismatch between theory and observation. In this work, we study the ability of generalized uncertainty principle (GUP) models, which are phenomenologically motivated models of quantum gravity, to address the cosmological constant problem. In particular, we focus on how these GUP models may change the phase space of QFT, and how this affects the momentum space integration of the zero-point energies of normal modes of fields. We point out several issues that make it unlikely that GUP models, in their current form, would be able to adequately address the cosmological constant problem. |
Friday, October 7, 2022 1:57PM - 2:09PM |
G03.00002: Minimum lengths with unmodified uncertainty principle and unmodified dispersion relation Douglas A Singleton, Michael Bishop, Joey Contreras Broad arguments indicate that quantum gravity should have a minimal length scale. In this talk we discuss a minimum length model by generalizing the time-position and energy-momentum operators while keeping much of the structure of quantum mechanics and relativity intact: the standard position-momentum commutator, the special relativistic time-position, and energy-momentum relationships all remain the same. Since the time-position and energy-momentum relationships for the modified operators remains the same, we retain a form of Lorentz symmetry. This avoids the constraints on these theories coming from lack of photon dispersion while holding the potential to address the Greisen-Zatsepin-Kuzmin (GZK) puzzle of ultra high energy cosmic rays. |
Friday, October 7, 2022 2:09PM - 2:21PM |
G03.00003: Improved Measurement of the Newtonian Gravitational Constant G Alexandra Papesh, Emily N Ord, Ricardo S Decca, C. D. Hoyle, Muchuan Hua The Newtonian gravitational constant, G, is a fundamental constant in nature that is known with the least precision of all fundamental constants. Over the last 200 years, its value has been repeatedly measured, however leading experiments have produced values which are incompatible with one another. Compared to the most precise experiment, some measured values differ by up to 50 times the experimental uncertainty. Recently, improved measurements have been made by two experiments with results that are consistent at the 12 ppm level. After examination of the methodology used in previous measurements, the research group at IUPUI, in collaboration with Cal Poly Humboldt, will use multiple approaches to determine G within a singular torsion pendulum apparatus. We expect to obtain a measurement at the 2 ppm level using these new methods. By continuing the use of a torsion pendulum apparatus, we also hope to better understand the current discrepancies among previous experimental results. This presentation will focus on the motivation behind obtaining a more precise measurement of G, as well as the design and current state of the experiment. |
Friday, October 7, 2022 2:21PM - 2:33PM |
G03.00004: Testing Gravitational Interactions Below Fifty Microns Tanner B Hooven, Kevin Chung, Abby Keltz, Alex Papesh, Claire Rodgers, Charles D Hoyle Attempts at unifying the Standard Model with General Relativity predict faults that could violate both the Weak Equivalence Principle (WEP) and the Gravitational Inverse Square Law (ISL). For unification theories to be investigated further, we must increase our understanding of gravity on a fundamental level. Undergraduate researchers and faculty at Cal Poly Humboldt are performing precise gravitational tests with sensitivity to new effects at and below a distance of 50μm. This experiment uses a torsion pendulum symetrically composed of two materials of equal mass placed opposite an oscillating attractor mass. The magnitude of torque measured on the pendulum due to gravitational attraction at such a scale could lead to deviational observations from the WEP and ISL. Recently, researchers have been focusing on minimizing noise and possible sources of extraneous interference by testing for and characterizing factors such as magnetic interactions, leveling issues, and temperature effects to increase the experiment's efficacy. |
Friday, October 7, 2022 2:33PM - 2:45PM |
G03.00005: Superconductor Meissner effects for gravito-electromagnetic fields in harmonic coordinates Nader (Nathan) Inan There is much discrepancy in the literature concerning the possibility of a superconductor expelling gravito-electromagnetic fields just as it expels electromagnetic fields in the Meissner effect.Contradicting results are found in at least 18 papers written collectively by more than 20 authors and published over the course of more than 55 years (from 1966 to the present year of 2022). The primary purpose of this paper is to carefully explain the reason for the discrepancies, and provide a single conclusive treatment which may bring coherence to the subject. The analysis begins with a covariant Lagrangian for spinless charged particles (Cooper pairs) in the presence of electromagnetic fields in curved space-time. It is known that such a Lagrangian can lead to a vanishing Hamiltonian. Alternatively, it is shown that using a "space+time" Lagrangian leads to an associated Hamiltonian with a canonical momentum and minimal coupling rule. Discrepancies between Hamiltonians obtained by various authors are resolved. The canonical momentum leads to a modified form of the London equations and London gauge that includes the effects of gravity. A key result is that the gravito-magnetic field is expelled from a superconductor with a penetration depth of on the order of the London penetration depth only when an appropriate magnetic field is also present. The gravitational flux quantum (fluxoid) in the body of a superconductor, and the quantized supercurrent in a superconducting ring, are also derived. Lastly, the case of a superconducting ring in the presence of a charged rotating mass cylinder is used as an example of applying the formalism developed. |
Friday, October 7, 2022 2:45PM - 2:57PM |
G03.00006: Visualizing merging binary black holes with SpECTRE Alex Carpenter Numerical-relativity models of merging black holes are important for predicting the gravitational waves that they emit and for understanding the behavior of the warped spacetime as the holes merge. Visualizations are important tools for understanding and confirming the output of simulations. In this presentation, I’ll present new visualizations of merging black holes using SpECTRE, an open-source, next-generation numerical-relativity code. In particular, I will show the methods used to visualize the curvature of space (characterized by the three-dimensional Ricci scalar), the lapse (the rate of flow of time), and discuss the progress I’ve made towards visualizing the emitted gravitational waves using the Newman-Penrose scalar Ѱ4. The Ѱ4 scalar will also be used as a comparison for the new CCE system being implemented within SpECTRE which propagates numerical data towards null infinity which in theory gives a more accurate waveform. |
Friday, October 7, 2022 2:57PM - 3:09PM |
G03.00007: Simulating Cosmological Axions in Primordial Magnetic Field Ameya Kunder, Benjamin R Safdi, Joshua Benabou Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. The axion, a particle billions of times lighter than the electron that was proposed in the 1970s to solve the strong CP problem in the neutron, is now proving to be a strong candidate to explain this missing mass in the universe. Although there have been several experimental searches that have been conducted to detect axions, these efforts have not yet been fruitful because of the largely unconstrained mass of the axion. While static lattice simulations of the axion string cosmology have been able to constrain the mass to a certain extent, adaptive mesh refinement (AMR) algorithms have been able to do so far more effectively by being able to achieve dynamical ranges that are several orders of magnitude more than the ones achievable by static lattices. Our goal is to measure the emission spectrum of axion radiation from the strings, which are topological defects generated by the axion field. This is because the axion radiation and its energy spectrum determine the dark matter abundance today. The simulations that have been run so far have not taken into account the effects of how an external magnetic field would affect the evolution of the axion strings which have been proposed to be superconducting. The goal of the project is to compute how the abundance of dark matter is affected by this property precisely using large-scale numerical simulations of superconducting axion strings in an expanding universe with primordial magnetic fields. |
Friday, October 7, 2022 3:09PM - 3:21PM |
G03.00008: Sensitivity to Dark Sector Scales from Gravitational Wave Signatures Jason Kumar, Bhaskar Dutta, James B Dent, Jack Runburg, Sumit Ghosh We consider gravitational wave signals produced by a first-order phase transition in a theory with a generic renormalizable thermal effective potential of power law form. We find the frequency and amplitude of the gravitational wave signal can be related in a straightforward manner to the parameters of the thermal effective potential. This leads to a general conclusion; if the mass of the dark Higgs is less than 1% of the dark Higgs vacuum expectation value, then the gravitational wave signal will be unobservable at all upcoming and planned gravitational wave observatories. |
Friday, October 7, 2022 3:21PM - 3:33PM |
G03.00009: Analysis of van Stockum Dust external solutions David S Lindsay We describe external vacuum solutions for radial cutoff of “van Stockum dust”, an infinitely long cylindrical rotating matter solution of Einstein’s equations of general relativity. These poorly explored spacetimes have been known for decades, but it seems that they have never been investigated in detail. They exhibit a number of exotic properties, which we described more fully in General Relativity and Gravitation (2016 48:121). Exotic properties include “time travel” in infinitely many cylindrical shells alternating with shells not permitting time travel. The radius of this “universe” is finite, with diverging gravitational tides and repulsion at the “edge.” |
Friday, October 7, 2022 3:33PM - 3:45PM |
G03.00010: The Exact Solution of Einstein's Gravitational Field Equation for a Space-Time Filled with Gravitating Matter of Density r(r, q, j) Lee w Schumann Abstract: In this article an exact solution of Einstein's gravitational field equation is derived in terms of the density of gravitating matter, r(r, q, j), instead of the gravitational mass, M. This solution of the gravitational field equation of general relativity provides analytical expressions, (predictions), describing many astronomical observations in the cosmos, a few of which are discussed in this article. The physical description of the gravitational field itself is extremely counter intuitive to our understanding of the gravitational field based on Newton's theory of gravity; yet the space-time described by this solution adds to our understanding of general relativity, cosmology, and the gravitational field in the four dimensional Riemann space-time. In addition the result contains serious implications for the fields of cosmology and quantum gravity. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700