Field Theory Research Team

Successful numerical simulations heavily depend on an increase of computer performance by improving algorithms and computational techniques. However, we now face a tough problem that the trend of computer architecture becomes large-scale hierarchical parallel structures consisting of tens of thousands of nodes which individually have increasing number of cores in CPU. We need to develop a new type of algorithms and computational techniques, which should be different from the conventional ones, to achieve better computer performance. For optimized use of K computer our research team aims at (1) developing an Monte Carlo algorithm to simulate physical system with negative weight effectively and (2) improving iterative methods to solve large system of linear equations. These technical development and improvement are carried out in the research of physics of elementary particles and nuclei based on lattice QCD (Quantum ChromoDynamics) which describes interactions between quarks known as elementary particles. Lattice QCD is one of the most advanced case in quantum sciences being formulated with the quantum field theory. Physics of elementary particles and nuclei is related to the early universe and the nucleosynthesis through Big Bang cosmology and their quantum properties are shared with the material physics at the atomic or molecular level.

Research Subjects

• Iterative solver for large system of linear equations
• Monte Carlro algorithm with sign problem
• QCD with finite temperature and finite density
• Nuclei in lattice QCD
• Physics beyond standard model

Publications

1. Y. Nakamura, K.-I. Ishikawa, Y. Kuramashi, T. Sakurai, H. Tadano:
   "Modified Block BiCGStab for Lattice QCD"
   Compuer Physics Commuication 183 (2012) 34
2. S. Takeda, Y. Kuramashi, A. Ukawa:
   "Phase of Quark Determinant in Lattice QCD with Finite Chemical Potential"
   Physical Review D85 (2012) 096008
3. PACS-CS Collaboration: S. Aoki et al.:
   "1+1+1 Flavor QCD+QED Simulation at the Physical Point"
   Physical Review D86 (2012) 034507
4. T. Yamazaki, K.-I. Ishikawa, Y. Kuramashi, A. Ukawa:
   "Helium Nuclei, Deuteron and Dineutron in 2+1 Flavor Lattice QCD"
   Physical Review D86 (2012) 074514