10 research outputs found
Gradient-flow scale setting with Wilson-clover twisted-mass fermions
We present a determination of the gradient flow scales w0 , t0‾‾√
and t0/w0 in isosymmetric QCD, making use of the gauge ensembles produced by the Extended Twisted Mass Collaboration (ETMC) with Nf=2+1+1
flavours of Wilson-clover twisted-mass quarks including configurations close to the physical point for all dynamical flavours. The simulations are carried out at three values of the lattice spacing and the scale is set through the PDG value of the pion decay constant, yielding w0=0.17383(63) fm, t0‾‾√=0.14436(61) fm and t0/w0=0.11969(62)
fm. Finally, fixing the kaon mass to its isosymmetric value, we determine the ratio of the kaon and pion leptonic decay constants to be fK/fπ=1.1995(44)
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Isospin-1/2 Dπ scattering and the lightest D 0 ∗ resonance from lattice QCD
Abstract: Isospin-1/2 Dπ scattering amplitudes are computed using lattice QCD, working in a single volume of approximately (3.6 fm)3 and with a light quark mass corresponding to mπ ≈ 239 MeV. The spectrum of the elastic Dπ energy region is computed yielding 20 energy levels. Using the Lüscher finite-volume quantisation condition, these energies are translated into constraints on the infinite-volume scattering amplitudes and hence enable us to map out the energy dependence of elastic Dπ scattering. By analytically continuing a range of scattering amplitudes, a D0∗ resonance pole is consistently found strongly coupled to the S-wave Dπ channel, with a mass m ≈ 2200 MeV and a width Γ ≈ 400 MeV. Combined with earlier work investigating the Ds0∗, and D0∗ with heavier light quarks, similar couplings between each of these scalar states and their relevant meson-meson scattering channels are determined. The mass of the D0∗ is consistently found well below that of the Ds0∗, in contrast to the currently reported experimental result
Towards High-Precision Parton Distributions from Lattice QCD via Distillation
We apply the Distillation spatial smearing program to the extraction of the unpolarized isovector valence PDF of the nucleon. The improved volume sampling and control of excited-states afforded by distillation leads to a dramatically improved determination of the requisite Ioffe-time Pseudo-distribution (pITD). The impact of higher-twist effects is subsequently explored by extending the Wilson line length present in our non-local operators to one half the spatial extent of the lattice ensemble considered. The valence PDF is extracted by analyzing both the matched Ioffe-time Distribution (ITD), as well as a direct matching of the pITD to the PDF. Through development of a novel prescription to obtain the PDF from the pITD, we establish a concerning deviation of the pITD from the expected DGLAP evolution of the pseudo-PDF. The presence of DGLAP evolution is observed once more following introduction of a discretization term into the PDF extractions. Observance and correction of this discrepancy further highlights the utility of distillation in such structure studies
筑波大学計算科学研究センター 平成28年度 年次報告書
まえがき …… 21 センター組織と構成員 …… 32 平成 28 年度の活動状況 …… 73 各研究部門の報告 …… 10I. 素粒子物理研究部門 …… 10II. 宇宙物理研究部門 …… 36III. 原子核物理研究部門 …… 64IV. 量子物性研究部門 …… 88V. 生命科学研究部門 …… 106 V-1. 生命機能情報分野 …… 106 V-2. 分子進化分野 …… 122VI. 地球環境研究部門 …… 140VII. 高性能計算システム研究部門 …… 154VIII. 計算情報学研究部門 …… 205 Ⅷ-1. データ基盤分野 …… 205 Ⅷ-2. 計算メディア分野 …… 22
Lattice Quantum Chromodynamics on Intel Xeon Phi based supercomputers
Preface
The aim of this master\u2019s thesis project was to expand the QPhiX library for twisted-mass fermions with and without clover term. To this end, I continued work initiated by Mario Schr\uf6ck et al. [63]. In writing this thesis, I was following two main goals. Firstly, I wanted to stress the intricate interplay of the four pillars of High Performance Computing: Algorithms, Hardware, Software and Performance Evaluation. Surely, algorithmic development is utterly important in Scientific Computing, in particular in LQCD, where it even outweighed the improvements made in Hardware architecture in the last decade\u2014cf. the section about computational costs of LQCD. It is strongly influenced by the available hardware\u2014think of the advent of parallel algorithms\u2014but in turn also influenced the design of hardware itself. The IBM BlueGene series is only one of many examples in LQCD. Furthermore, there will be no benefit from the best algorithms, when one cannot implement the ideas into correct, performant, user-friendly, read- and maintainable (sometimes over several decades) software code. But again, truly outstanding HPC software cannot be written without a profound knowledge of its target hardware. Lastly, an HPC software architect and computational scientist has to be able to evaluate and benchmark the performance of a software program, in the often very heterogeneous environment of supercomputers with multiple software and hardware
layers. My second goal in writing this thesis was to produce a self-contained introduction into the computational aspects of LQCD and in particular, to the features of QPhiX, so the reader would be able to compile, read and understand the code of one truly amazing pearl of HPC [40]. It is a pleasure to thank S. Cozzini, R. Frezzotti, E. Gregory, B. Jo\uf3, B. Kostrzewa, S. Krieg,
T. Luu, G. Martinelli, R. Percacci, S. Simula, M. Ueding, C. Urbach, M. Werner, the Intel company for providing me with a copy of [55], and the J\ufclich Supercomputing Center for granting me access to their KNL test cluster DEE
Proceedings, MSVSCC 2015
The Virginia Modeling, Analysis and Simulation Center (VMASC) of Old Dominion University hosted the 2015 Modeling, Simulation, & Visualization Student capstone Conference on April 16th. The Capstone Conference features students in Modeling and Simulation, undergraduates and graduate degree programs, and fields from many colleges and/or universities. Students present their research to an audience of fellow students, faculty, judges, and other distinguished guests. For the students, these presentations afford them the opportunity to impart their innovative research to members of the M&S community from academic, industry, and government backgrounds. Also participating in the conference are faculty and judges who have volunteered their time to impart direct support to their students’ research, facilitate the various conference tracks, serve as judges for each of the tracks, and provide overall assistance to this conference. 2015 marks the ninth year of the VMASC Capstone Conference for Modeling, Simulation and Visualization. This year our conference attracted a number of fine student written papers and presentations, resulting in a total of 51 research works that were presented. This year’s conference had record attendance thanks to the support from the various different departments at Old Dominion University, other local Universities, and the United States Military Academy, at West Point. We greatly appreciated all of the work and energy that has gone into this year’s conference, it truly was a highly collaborative effort that has resulted in a very successful symposium for the M&S community and all of those involved. Below you will find a brief summary of the best papers and best presentations with some simple statistics of the overall conference contribution. Followed by that is a table of contents that breaks down by conference track category with a copy of each included body of work. Thank you again for your time and your contribution as this conference is designed to continuously evolve and adapt to better suit the authors and M&S supporters.
Dr.Yuzhong Shen Graduate Program Director, MSVE Capstone Conference Chair
John ShullGraduate Student, MSVE Capstone Conference Student Chai