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RIKEN Advanced Institute for Computational Science

# Field Theory Research Team

Team Leader: Yoshinobu Kuramashi (D.Sci.)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 a numerical algorithm to effectively simulate physical system with negative weight in partition function 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.

## Main Research Field

Mathematical and physical sciences

## Related Research Fields

Interdisciplinary science and engineering

## Research Subjects

- Iterative solver for large system of linear equations
- Numerical algorithm based on tensor network scheme
- Physics of elementary particle and nuclei with lattice gauge theories

## Selected Publications

- Y. Nakamura, K.-I. Ishikawa, Y. Kuramashi, T. Sakurai, H. Tadano.:

"Modified Block BiCGStab for Lattice QCD"

Computer Physics Commuication 183 (2012) 34. - S. Takeda, Y. Kuramashi, A. Ukawa.:

"Phase of Quark Determinant in Lattice QCD with Finite Chemical Potential"

Physical Review D85 (2012) 096008. - PACS-CS Collaboration: S. Aoki et al.:

"1+1+1 Flavor QCD+QED Simulation at the Physical Point"

Physical Review D86 (2012) 034507. - 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. - X.-Y. Jin, Y. Kuramashi, Y. Nakamura, S. Takeda, A. Ukawa.:

"Finite Size Scaling Study of Nf=4 Finite Density QCD on the Lattice"

Physical Review D88 (2013) 094508. - Y. Shimizu and Y. Kuramashi.:

"Grassmann Tensor Renormalization Group Approach to One-Flavor Lattice Schwinger Model"

Physical Review D90 (2014) 014508. - Y. Shimizu and Y. Kuramashi.:

"Critical Behavior of the Lattice Schwinger Model with a Topological Term at θ=π using the Grassmann Tensor Renormalization Group"

Physical Review D90 (2014) 074503. - T. Yamazaki, K.-I. Ishikawa, Y. Kuramashi, A. Ukawa.:

"Study of Quark Mass Dependence of Binding Energy for Light Nuclei in 2+1 Flavor Lattice QCD"

Physical Review D92 (2015) 014501. - X.-Y. Jin, Y. Kuramashi, Y. Nakamura, S. Takeda, A. Ukawa.:

"Critical Endpoint of the Finite Temperature Phase Transition for Three Flavor QCD"

Physical Review D91 (2015) 014508. - X.-Y. Jin, Y. Kuramashi, Y. Nakamura, S. Takeda, A. Ukawa.:

"Curvature of the Critical Line on the Plane of Quark Chemical Potential and Pseudo Scalar Meson Mass for Three-Flavor QCD"

Physical Review D92 (2015) 114511.

## Lab Members

### Principal Investigator

- Yoshinobu Kuramashi
- Team Leader

### Core Members

- Hiroya Suno
- Research Scientist
- Yoshifumi Nakamura
- Research Scientist
- Eigo Shintani
- Research Scientist
- Yuya Shimizu
- Postdoctoral Researcher
- Yusuke Yoshimura
- Postdoctoral Researcher
- Shoichi Sasaki
- Visiting Scientist
- Takeshi Yamazaki
- Visiting Scientist
- Kenichi Ishikawa
- Visiting Scientist
- Shinji Takeda
- Visiting Scientist