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Breaking and restoration of rotational symmetry on the lattice for bound state multiplets

Physical review d 2014年第3期90卷 034507-034507页

作者： Bing-Nan Lu Timo A. Lähde dean Lee Ulf-G. Meißner Institute for Advanced Simulation Institut für Kernphysik and Jülich Center for Hadron Physics Forschungszentrum Jülich D-52425 Jülich Germany Department of Physics North Carolina State University Raleigh North Carolina 27695 USA Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn D-53115 Bonn Germany JARA-High Performance Computing Forschungszentrum Jülich D-52425 Jülich Germany

We explore the breaking of rotational symmetry on the lattice for bound state energies and practical methods for suppressing this breaking. We demonstrate the general problems associated with lattice discretization errors and finite-volume errors using an α cluster model for Be8 and C12. We consider the two and three α-particle systems and focus on the lowest states with nonzero angular momentum which split into multiplets corresponding to different irreducible representations of the cubic group. We examine the dependence of such splittings on the lattice spacing and box size. We find that lattice spacing errors are closely related to the commensurability of the lattice with the intrinsic length scales of the system. We also show that rotational symmetry breaking effects can be significantly reduced by using improved lattice actions, and that the physical energy levels are accurately reproduced by the weighted averages of the spin multiplets.

关键词： BrOKEN symmetry (Physics) LATTICE theory BOUNd states (Quantum mechanics) MOLECULAr rotation ANGULAr momentum (Nuclear physics) dISCrETIZATION methods

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Breaking and restoration of rotational symmetry for irreducible tensor operators on the lattice

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Physical review d 2015年第1期92卷 014506-014506页

We study the breaking of rotational symmetry on the lattice for irreducible tensor operators and practical methods for suppressing such breaking. We illustrate the features of the general problem using an α cluster model for Be8. We focus on the lowest states with nonzero angular momentum and examine the matrix elements of multipole moment operators. We show that reduced matrix elements are well reproduced by averaging over all possible orientations of the quantum state. This averaging is performed in terms of a sum of matrix elements weighted by the Clebsch-Gordan coefficients of each orientation. For our α cluster model, we find that the effects of rotational symmetry breaking can be largely eliminated for lattice spacings of a≤1.7 fm, and we expect similar improvement for lattice Monte Carlo calculations.

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Hyperon-nucleon interaction within chiral effective field theory revisited

arXiv

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arXiv 2019年

作者： Haidenbauer, Johann Meißner, U.-G. Nogga, A. Jülich Center for Hadron Physics Forschungszentrum Jülich JülichD-52425 Germany Helmholtz Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn BonnD-53115 Germany Tbilisi State University Tbilisi0186 Georgia JARA-High Performance Computing Forschungszentrum Jülich JülichD-52425 Germany

The ΛN and ΣN interactions are considered at next-to-leading order in SU(3) chiral effective field theory. different options for the low-energy constants that determine the strength of the contact interactions are explored. Two variants are analysed in detail which yield equivalent results for ΛN and ΣN scattering observables but differ in the strength of the ΛN → ΣN transition potential. The influence of this difference on predictions for light hypernuclei and on the properties of the Λ and Σ hyperons in nuclear matter is investigated and discussed. The effect of the variation in the potential strength of the ΛN-ΣN coupling (also called Λ − Σ conversion) is found to be moderate for the considered 3ΛH and 4ΛHe hypernuclei but sizable in case of the matter properties. Further, the size of three-body forces and their relation to different approaches to hypernuclear interactions is discussed. Copyright © 2019, The Authors. All rights reserved.

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Simulations of 3d flow and sediment transport in a fishway

Simulations of 3D flow and sediment transport in a fishway

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19th IASTEd International Conference on Modelling and Simulation, MS 2008

作者： Chang, Wen-Yi Lien, Ho-Cheng Lee, Lung-Cheng Tsai, Whey-Fong Lai, Jihn-Sung Tan, Yih-Chi Guo, Wen-dar National Center for High-Performance Computing Hsinchu Science Park No. 7 R and D Rd. VI Hsinchu 30076 Taiwan Department of Bioenvironmental Systems Eng. National Taiwan University Taipei City 106 Taiwan WG-ENV ICID. SG Chinese Taipei Committee China Hydrotech Research Institute Taiwan Dept. of Bioenvironmental System Eng. National Taiwan University Taipei City 106 Taiwan Hydrotech Research Institute National Taiwan University Taipei City 106 Taiwan

ISBN: (纸本)9780889867420

A 3d two-phase flow numerical model based on the large eddy simulation is developed to deal with the free surface problems by using the surface capturing method. In addition, the advection-diffusion equation is incorporated into the model to deal with the sediment transport problems. For validations, the analytical solutions of re-suspended sediment concentration distributions by Hjemfelt and Lenau (1970), and the measured data of deposited sediment concentration distributions by Jobson and Sayre (1970) are employed for comparisons. Then, this numerical model is used for simulation of 3d flow and sediment transport in a fish-bone-type fishway. The flow patterns and sediment transport processes in a fishbone-type fishway are illustrated.

关键词： Sediment transport

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First-principle calculations of dark matter scattering off light nuclei

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Physical review C 2017年第3期96卷 035805-035805页

作者： C. Körber A. Nogga J. de Vries Institute for Advanced Simulations 4 Institute für Kernphysik 3 Jülich Center for Hadron Physics and JARA–High Performance Computing Forschungszentrum Jülich D-52425 Jülich Germany Department of Physics and Astronomy Ohio University Athens Ohio 45701 USA Nikhef Theory Group Science Park 105 1098 XG Amsterdam The Netherlands

We study the scattering of dark matter particles off various light nuclei within the framework of chiral effective field theory. We focus on scalar interactions and include one- and two-nucleon scattering processes whose form and strength are dictated by chiral symmetry. The nuclear wave functions are calculated from chiral effective field theory interactions as well and we investigate the convergence pattern of the chiral expansion in the nuclear potential and the dark matter–nucleus currents. This allows us to provide a systematic uncertainty estimate of our calculations. We provide results for H2, H3, and He3 nuclei, which are theoretically interesting, and the latter is a potential target for experiments. We show that two-nucleon currents can be systematically included but are generally smaller than predicted by power counting and suffer from significant theoretical uncertainties even in light nuclei. We demonstrate that accurate high-order wave functions are necessary in order to incorporate two-nucleon currents.

关键词： Chiral perturbation theory Nuclear astrophysics Nuclear forces Nucleon-nucleon interactions Particle dark matter A ≤ 5 Ab initio calculations

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Nuclear Binding Near a Quantum Phase Transition

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Physical review Letters 2016年第13期117卷 132501-132501页

作者： Serdar Elhatisari Ning Li Alexander rokash Jose Manuel Alarcón dechuan du Nico Klein Bing-nan Lu Ulf-G. Meißner Evgeny Epelbaum Hermann Krebs Timo A. Lähde dean Lee Gautam rupak Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn D-53115 Bonn Germany Institute for Advanced Simulation Institut für Kernphysik and Jülich Center for Hadron Physics Forschungszentrum Jülich D-52425 Jülich Germany Institut für Theoretische Physik II Ruhr-Universität Bochum D-44870 Bochum Germany JARA–High Performance Computing Forschungszentrum Jülich D-52425 Jülich Germany Department of Physics North Carolina State University Raleigh North Carolina 27695 USA Department of Physics and Astronomy and HPC2 Center for Computational Sciences Mississippi State University Mississippi State Mississippi 39762 USA

How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (He4 nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.

关键词： Nuclear forces Nuclear many-body theory Nuclear structure & decays Monte Carlo methods

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Flood inundation simulations in the lowlands of the Changhua County, Taiwan

Flood inundation simulations in the lowlands of the Changhua...

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19th IASTEd International Conference on Modelling and Simulation, MS 2008

作者： Lien, Ho-Cheng Chang, Wen-Yi Tsai, Whey-Fong Lai, Jihn-Sung Chang, Shiang-Kuan Pan, Tsung-Yi Tan, Yih-Chi National Center for High-Performance Computing Hsinchu Science Park No. 7 R and D Rd. VI Hsinchu 30076 Taiwan Department of Bioenvironmental Systems Eng. National Taiwan University Taipei City 106 Taiwan Department of Bioenvironmental System Engineering National Taiwan University Taipei City 106 Taiwan Disaster Research Center National Taiwan University Taipei City 106 Taiwan WG-ENV ICID. SG Chinese Taipei Committee China Hydrotech Research Institute Taiwan Dept. of Bioenvironmental Systems Eng. National Taiwan University Taipei City 106 Taiwan

ISBN: (纸本)9780889867420

A two-dimensional (2d) inundation model is applied to simulate flood inundation due to typhoon storm rainfall in the Changhua county located in the lowlands of western Taiwan. Using collected data in the Changhua county, the inundation-prone areas and depths are simulated to calibrate parameters of the 2d inundation model. The calibrated parameters are used to simulate 5-year and 200-year return-period potential inundation. With different precision of digital Elevation Model (dEM) data for land surface topography, in a local drainage system inundation depths are simulated to analyze the effects of grid size related to dEM accuracy. The potential inundation-prone areas can be simulated and analyzed in advance to provide the disaster prevention information for planning of emergency response and design of flood protection.

关键词： Floods

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Ab Initio Calculation of the Spectrum and Structure of O16

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Physical review Letters 2014年第10期112卷 102501-102501页

作者： Evgeny Epelbaum Hermann Krebs Timo A. Lähde dean Lee Ulf-G. Meißner Gautam rupak Institut für Theoretische Physik II Ruhr-Universität Bochum D-44870 Bochum Germany Institute for Advanced Simulation Institut für Kernphysik and Jülich Center for Hadron Physics Forschungszentrum Jülich D-52425 Jülich Germany Department of Physics North Carolina State University Raleigh North Carolina 27695 USA Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn D-53115 Bonn Germany JARA-High Performance Computing Forschungszentrum Jülich D-52425 Jülich Germany Department of Physics and Astronomy Mississippi State University Mississippi State Mississippi 39762 USA

We present ab initio lattice calculations of the low-energy even-parity states of O16 using chiral nuclear effective field theory. We find good agreement with the empirical energy spectrum, and with the electromagnetic properties and transition rates. For the ground state, we find that the nucleons are arranged in a tetrahedral configuration of alpha clusters. For the first excited spin-0 state, we find that the predominant structure is a square configuration of alpha clusters, with rotational excitations that include the first spin-2 state.

关键词： Ground state

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Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell

arXiv

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arXiv 2023年

作者： Leidi, G. Andrassy, r. Higl, J. Edelmann, P.V.F. röpke, F.K. Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 HeidelbergD-69118 Germany High-Performance Computing Center Stuttgart Nobelstraße 19 Stuttgart70569 Germany Los Alamos National Laboratory Los AlamosNM87545 United States Zentrum für Astronomie der Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 HeidelbergD-69120 Germany

Convection is one of the most important mixing processes in stellar interiors. Hydrodynamic mass entrainment can bring fresh fuel from neighboring stable layers into a convection zone, modifying the structure and evolution of the star. Because flows in stellar convection zones are highly turbulent, multidimensional hydrodynamic simulations are fundamental to accurately capture the physics of mixing processes. Under some conditions, strong magnetic fields can be sustained by the action of a turbulent dynamo, adding another layer of complexity and possibly altering the dynamics in the convection zone and at its boundaries. In this study, we used our fully compressible Seven-League Hydro code to run detailed and highly resolved three-dimensional magnetohydrodynamic simulations of turbulent convection, dynamo amplification, and convective boundary mixing in a simplified setup whose stratification is similar to that of an oxygen-burning shell in a star with an initial mass of 25 M☉. We find that the random stretching of magnetic field lines by fluid motions in the inertial range of the turbulent spectrum (i.e., a small-scale dynamo) naturally amplifies the seed field by several orders of magnitude in a few convective turnover timescales. during the subsequent saturated regime, the magnetic-to-kinetic energy ratio inside the convective shell reaches values as high as 0.33, and the average magnetic field strength is ∼1010 G. Such strong fields efficiently suppress shear instabilities, which feed the turbulent cascade of kinetic energy, on a wide range of spatial scales. The resulting convective flows are characterized by thread-like structures that extend over a large fraction of the convective shell. The reduced flow speeds and the presence of magnetic fields with strengths up to 60% of the equipartition value at the upper convective boundary diminish the rate of mass entrainment from the stable layer by ≈ 20% as compared to the purely hydrodynamic case. Copyright © 2023,

关键词： Magnetohydrodynamics

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Pseudoscalar-pole contributions to the muon g - 2 at the physical point 39

Pseudoscalar-pole contributions to the muon g - 2 at the phy...

引用

39th International Symposium on Lattice Field Theory, LATTICE 2022

作者： Burri, S. Kanwar, G. Alexandrou, C. Bacchio, S. Bergner, G. Finkenrath, J. Gasbarro, A. Hadjiyiannakou, K. Jansen, K. Kostrzewa, B. Koutsou, G. Ottnad, K. Petschlies, M. Pittler, F. Steffens, F. Urbach, C. Wenger, U. Albert Einstein Center for Fundamental Physics Institute for Theoretical Physics University of Bern Sidlerstrasse 5 BernCH-3012 Switzerland Department of Physics University of Cyprus Nicosia20537 Cyprus Computation-based Science and Technology Research Center The Cyprus Institute 20 Konstantinou Kavafi Street Nicosia2121 Cyprus University of Jena Institute for Theoretical Physics Max-Wien-Platz 1 JenaD-07743 Germany Deutsches Elektronen-Synchrotron DESY Platanenallee 6 Zeuthen15738 Germany High Performance Computing and Analytics Lab Rheinische Friedrich-Wilhelms-Universität Bonn Friedrich-Hirzebruch-Allee 8 BonnD-53115 Germany PRISMA+ Cluster of Excellence Institut für Kernphysik Johannes Gutenberg-Universität Mainz Johann-Joachim-Becher-Weg 45 MainzD-55128 Germany Rheinische Friedrich-Wilhelms-Universität Bonn Nussallee 14-16 BonnD-53115 Germany Bethe Center for Theoretical Physics Rheinische Friedrich-Wilhelms-Universität Bonn Wegelerstraße 10 BonnD-53115 Germany

Pseudoscalar-pole diagrams are an important component of estimates of the hadronic light-by-light (HLbL) contribution to the muon g - 2. We report on our computation of the transition form factors FP→γ*γ* for the neutral pseudoscalar mesons P = π0 and η. The calculation is performed using twisted-mass lattice QCd with physical quark masses. On the lattice, we have access to a broad range of (space-like) photon four-momenta and therefore produce form factor data complementary to the experimentally accessible single-virtual direction, which directly leads to an estimate of the pion- and η-pole components of the muon g - 2. For the pion, our result for the g - 2 contribution in the continuum is comparable with previous lattice and data-driven determinations, with combined relative uncertainties below 10%. For the η meson, we report on a preliminary determination from a single lattice spacing. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-Noderivatives 4.0 International License (CC BY-NC-Nd 4.0).

关键词： Poles

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