Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session G10: Computational Methods and their Implementation in Physics |
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Sponsoring Units: DCOMP Chair: Liwei Ji, Rochester Institute of Technology Room: Marquette I - 2nd Floor |
Sunday, April 16, 2023 10:45AM - 10:57AM |
G10.00001: Transitions in (1+1) light front Φ4 theory using quantum computing method Mengyao Huang, James P Vary, Wenyang Qian We study the phase transitions in (1+1) Φ4 theory using discretized light-cone quantization (DLCQ) with both classical computing and quantum computing methods. The transition at the ground state from a single-particle dominant state to a three-particle dominant state can be revealed by the parton distribution function and indicated by crossing of mass square eigenvalues at a strong coupling. The critical coupling is a function of resolution and will be extrapolated to the continuum limit. We discuss quantum computing as a method of exploring quantum phase transition in the light-front (1+1) Φ4 theory. |
Sunday, April 16, 2023 10:57AM - 11:09AM |
G10.00002: Multi-nucleon structure and dynamics via quantum computing Weijie Du, James P Vary We propose a method to compute the structure and dynamics for second-quantized many-nucleon Hamiltonians on near-term noisy intermediate scale quantum computers. We develop an oracle-based Hamiltonian input model that computes the many-nucleon states and non-zero Hamiltonian matrix elements of the many-nucleon system. With our Fock-state based input model, we show how to implement the sparse matrix simulation algorithms to calculate the dynamics of the second-quantized many-nucleon Hamiltonian. Based on the dynamics simulation methods, we also present the methodology for structure calculations of the many-nucleon system. In this work, we provide explicit design of our input model of the second-quantized Hamiltonian within a direct encoding scheme that maps the occupation of each available single-particle state in the many-nucleon state to the state of specific qubit in quantum register. We analyze our method and provide the asymptotic cost in computing resources for structure and dynamics calculations of many-nucleon systems. For pedagogical purpose, we demonstrate our method with two model problems in restricted model spaces. |
Sunday, April 16, 2023 11:09AM - 11:21AM |
G10.00003: Electrostatic and Gravitational Solves Using PETSc-PIC Daniel Finn Numerical solutions to the Vlasov-Poisson equations have important applications in the fields of plasma physics, solar physics and cosmology. The goal of this research is to develop a structure-preserving, electrostatic and gravitational Vlasov-Poisson(-Landau) model using the Portable, Extensible Toolkit for Scientific Computation (PETSc) and study the presence of Landau damping in a variety of systems, such as thermonuclear fusion reactors and galactic dynamics. The PETSc Particle-In-Cell (PETSc-PIC) model is a highly-scalable, structure preserving PIC method with multigrid capabilities. In the PIC method, a hybrid discretization is constructed with a grid of finitely supported basis functions to represent the electric, magnetic and/or gravitational fields, and a distribution of radial basis functions to represent the particle field. Collisions are added to the formulation by means of a particle-basis Landau collision operator, recently added to the PETSc library. |
Sunday, April 16, 2023 11:21AM - 11:33AM |
G10.00004: Visualizing Binary Black Hole Mergers with SpECTRE Alex Carpenter, Geoffrey Lovelace Numerical-relativity models of merging black holes are necessary for predicting the gravitational waves that they emit and for understanding the behavior of the strongly warped spacetime as the holes merge. Visualizations are important tools for understanding the output of simulations. In this talk, I will 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 the emitted gravitational waves using the Newman-Penrose scalar Ψ4. I will also discuss progress towards extracting Ψ4 on a Strahlkorper surface which will allow us to compare gravitational waveforms with the output of other numerical-relativity codes and with SpECTRE’s Cauchy Characteristic Evolution (CCE) system. |
Sunday, April 16, 2023 11:33AM - 11:45AM |
G10.00005: Neutron Star Tests with the Nmesh Program Ananya Adhikari, Wolfgang H Tichy, liwei Ji We present the results from recent single Neutron Star test evolutions that we have performed using the discontinuous Galerkin method based Nmesh program. These include tests for the single Neutron Star to check long-time stability equilibrium configurations, consistency under perturbations, migration of an unstable configuration to a stable one and evolution of a boosted star. To allow for changing gravitational fields, we use the Generalized Harmonic system to evolve the metric of the Neutron star. We apply refinement to the mesh as necessary and relevant. We also study the effect of other aspects, such as application of filters, positivity limiters or the MRS limiter, and the use of an artificial atmosphere, on the runs. |
Sunday, April 16, 2023 11:45AM - 11:57AM |
G10.00006: Efficient Parallel Numerical Simulations of the Einstein Equations in Spherical Coordinates Liwei Ji We present a new parallel filter that we use to ameliorate the severe |
Sunday, April 16, 2023 11:57AM - 12:09PM |
G10.00007: Importing Binary Neutron Star initial data from SGRID into the Einstein Toolkit Michal Pirog, Wolfgang H Tichy We are investigating Binary Neutron Star mergers by performing numerical simulations using the Einstein Toolkit (ET) framework - Cactus. |
Sunday, April 16, 2023 12:09PM - 12:21PM |
G10.00008: An overview of Celeritas: a novel GPU Monte Carlo detector simulation code Stefano C. Tognini, Seth R Johnson, Soon Yung Jun, Amanda L Lund, Thomas M Evans, Philippe Canal, Paul K Romano, Guilherme Lima The next-generation of High Energy Physics (HEP) experiments will rely on a vast increase in detector complexity and data collection, leading to an unprecedented amount of computing storage and processing capacity needs. Contemporary increases in computing capacity are primarily due to the use of heterogeneous architectures that rely on the high performance-per-Watt of GPUs. Celeritas, a new GPU-optimized detector simulation code, seeks to unlock the resources of DOE's Leadership Computing Facilities (LCFs) and the next generation of computing grid hardware for HEP experiments. Early results show a 40× speedup factor for standalone EM simulations on LCF computers when using GPUs. This talk will provide an overview of Celeritas, focusing on its physics capabilities and integration with the CPU-based detector simulation code Geant4. Current Celeritas' electromagnetic (EM) physics models for electrons, positrons, and photons will be verified against Geant4, with an additional verification for coupled offloading, where Geant4 processes hadronic and decay physics but sends EM particles to Celeritas, with an estimated speedup of 2–3× compared to a Geant4-only run. The presentation will also preview future plans for integration with HEP experiments, of which EM offloading is the first step. |
Sunday, April 16, 2023 12:21PM - 12:33PM |
G10.00009: Gauge conditions for Generalized Harmonic Evolution that reduce the deformations of the apparent horizon. Himanshu Chaudhary, Saul A Teukolsky, Mark A Scheel, Robert P Owen, Nils Deppe Good gauge conditions are essential for stable numerical relativity simulations. The choice of gauge also affects the coordinate shape of apparent horizons. For codes using spectral methods, like SpEC and SpECTRE, the apparent horizons are represented using spherical harmonics. Having apparent horizons close to spherical is desirable because they can then be accurately represented using low-order spherical harmonics, which will in turn make the code more efficient. In the generalized harmonic formalism, the stability of the system restricts the gauge conditions that we can use. We instead use gauge driver extension of the generalized harmonic formalism, which allows us to set any gauge by giving a target for the contracted Christoffel symbol $Gamma_a$ . We set the target $Gamma_a$ around each apparent horizon to be that of a Kerr black hole of the correct mass and spin. Using this gauge, we can keep the shape of both apparent horizons close to a sphere during the evolution, substantially reducing the number of spherical harmonics required to represent them. The next step is to try setting the gauge directly without using the gauge driver, which would make the simulations even more efficient. |
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