Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session X11: Computational Methods for Particle and Nuclear Physics |
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Sponsoring Units: DCOMP Chair: Alexei Bazavov, Michigan State University Room: A220-221 |
Tuesday, April 17, 2018 10:45AM - 10:57AM |
X11.00001: Challenges and Opportunities in HEP Software and Computing Mark Neubauer, Peter Elmer, Michael Sokoloff Realizing the physics goals of the planned or upgraded experiments in high-energy physics (HEP) over the next 10 years will require the HEP community to address a number of challenges in the area of software and computing. In order to identify and prioritize R&D in scientific software and computing infrastructure, a broad community planning process has been undertaken within HEP. In this talk, we present some of the challenges and opportunities in computing and software for realizing the full scientific potential of HEP experiments over the next decades. We discuss the Community White Paper which provides a community roadmap for HEP software and computing R&D for the 2020s -- an activity organized under the umbrella of the HEP Software Foundation. Finally, we describe the conceptualization of a possible NSF HEP Scientific Software Innovation Institute within the US designed to address software and computing challenges for the high-luminosity running of the Large Hadron Collider. [Preview Abstract] |
Tuesday, April 17, 2018 10:57AM - 11:09AM |
X11.00002: A Method for Storing Monte Carlo Cross Section Information in the CMS Experiment Shawn Zaleski The Compact Muon Solenoid (CMS) experiment generators group has created a Cross Section Database (XSDB) Tool to store information related to it’s centrally produced Monte Carlo (MC) samples. XSDB utilizes a non-relational database back-end to store the MC sample information and FLASK web development software for the front-end user interface. Users within the CMS community now have the ability to easily search for cross section information related to a sample of interest from amongst thousands of centrally produced MC samples. In this talk, we explain the use of XSDB and how its features make searching for MC cross section information in CMS simple and easy. [Preview Abstract] |
Tuesday, April 17, 2018 11:09AM - 11:21AM |
X11.00003: Simulation and Design of the next phase of Project 8, a Direct Neutrino Mass Measurement Experiment Tim Wendler The Project 8 experiment seeks to determine the absolute neutrino mass scale via the precise measurement of the electron energy in beta decays. We have developed a novel technique called Cyclotron Radiation Emission Spectroscopy (CRES), which allows single electron detection and characterization through the measurement of cyclotron radiation emitted by magnetically-trapped electrons produced by a gaseous radioactive source. The advantages of this technique include excellent energy resolution and low backgrounds. We present an overview of the Project 8 experimental program, and highlight recent advances in the development of the next phase, a “Large Volume Demonstrator” that will be used to validate the technique’s scalability. The demonstrator consists of a tritium-filled 200 $\mathrm{cm}^{3}$ volume, surrounded by magnetic trap coils and antenna arrays, all within an MRI magnet. Experimental parameters like uniform detector coverage and the reduction of Doppler effects are obtained via simulations using High Performance Computing. We discuss geometric constraints and design optimizations to maximize SNR at the tritium endpoint energy range. This work is supported by the U.S. D.O.E Office of Nuclear Physics and the National Science Foundation. [Preview Abstract] |
Tuesday, April 17, 2018 11:21AM - 11:33AM |
X11.00004: Computational Developments for Coupled Cluster Theory With Triples and Three-Body Forces Justin Lietz, Morten Hjorth-Jensen, Gustav Jansen Solving the many-body Schr$\ddot{\text{o}}$dinger equation for infinite matter systems is a great tool for producing observables about dense neutron matter. Quantities like the nuclear equation of state and single particle addition and removal energies can be calculated from a simulated periodic box of nuclear matter. Unfortunately, solving this problem exactly with a given basis set scales exponentially with the basis size, making the problem computationally infeasible. The coupled cluster (CC) approximation has had great success here as it scales polynomially with basis size, allowing for more physical calculations to be done. Recently however, higher order CC methods are being used to increase the precision of the solution, and three-body nuclear forces are often needed to gain reliably accurate observables. This increases the polynomial order of the CC approximation to the point that even modest basis sets demand extreme amounts of computational power and memory. Getting converged results for CC with full triples excitations and three-body forces becomes a computational challenge of efficient storage of large sparse tensors across many computational nodes and contracting these tensors using data structures that allow for scalable many-core tensor contraction via GPUs. [Preview Abstract] |
Tuesday, April 17, 2018 11:33AM - 11:45AM |
X11.00005: Topological charge and cooling scales in pure SU(2) lattice gauge theory David Clarke, Bernd Berg Recent pure SU(3) and SU(2) studies demonstrated that standard cooling can be used to define a new reference scale, the cooling scale, in a similar manner as the gradient flow. In a continuation of our SU(2) study, we calculate topological charge and topological susceptibility on equilibrated lattices up to size $60^4$ and $\beta=2.928$ by smoothing configurations with standard cooling. Our estimates appear to be reliable at $\beta$ values and lattice sizes which are larger than those used in previous SU(2) studies of this topic. Differences between cooling scales calculated in different topological sectors are too small to be detectable within our statistical uncertainty. [Preview Abstract] |
Tuesday, April 17, 2018 11:45AM - 11:57AM |
X11.00006: A Discontinuous Galerkin Method for Spectral Neutrino Transport Eirik Endeve, Ran Chu, Cory Hauck, Anthony Mezzacappa We are developing methods for simulation of multi-dimensional neutrino transport in nuclear astrophysics applications (e.g., core-collapse supernovae and binary neutron star mergers). We aim to develop methods that are accurate and robust. Here we consider a multi-group two-moment model, where the spectral particle density $\mathcal{N}$ and flux $\boldsymbol{\mathcal{F}}$ -- angular moments of a phase space distribution function $f$ -- approximates the radiation field in a computationally tractable manner. Our approach is based on the Runge-Kutta discontinuous Galerkin method\footnote{Cockburn \& Shu 2001, J. Sci. Comput. {\bf 16}, 173-261}. Building on our previous work\footnote{Endeve et al. 2015, JCP, {287}, 151-183}, we are developing a method that maintains realizable solutions in the sense that $\mathcal{N}$ and $\boldsymbol{\mathcal{F}}$ remains consistent with moments of an underlying Fermi-Dirac distribution (satisfying $0\le f \le1$). We present details of the physical model, the numerical method, and show preliminary numerical results. [Preview Abstract] |
Tuesday, April 17, 2018 11:57AM - 12:09PM |
X11.00007: On the Schur complement of the nearest Kronecker product preconditioner for elliptic boundary value problems Pablo Brubeck The numerical solution of elliptic partial differential equations requires the inversion of large matrices, which is computationally expensive. An elegant and efficient domain decomposition method for almost-separable elliptic PDEs is presented. Suitable preconditioners for continuous Galerkin methods are obtained through exploiting characteristics of the matrix structure. First, the elliptic operator may be well approximated at each subdomain as a sum of two Kronecker products, which may be efficiently obtained via the Lanczos SVD algorithm. The Nearest Kronecker Product (NKP) approximation represents an ideal preconditioner given the minimal computational cost required for inversion, as it can be factored in a separable fashion. Second, the Schur complement method allows the parallel solution of each subdomain by decoupling the interface degrees of freedom via block-Gaussian elimination. The explicit computation of the Schur complement for the NKP is enormously simplified, making its LU decomposition feasible to be used to invert the preconditioner in an iterative solver. Most solutions can be obtained with 30 or less GMRES iterations, disregarding the number of grid points. The method is then utilized to yield eigenmodes for the 2D Laplacian in composite domains. [Preview Abstract] |
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