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- Yasuhiro Idomura, Motoki Nakata, +8 authors Naoyuki Shida
- IJHPCA
- 2014

- Masanori Nunami
- 2001

One of the the basic assumptions in perturbative renormalization as a physical concept in a trivial, perturbatively renormalizable theory is that the intrinsic cutoff of the theory is so large that the nonperturbative effects due to the finite intrinsic cutoff become very small in the infrared regime. We treat trivial theories, including unrenormalizable… (More)

- Tatsuki Matsui, Hideyuki Usui, Toseo Moritaka, Masanori Nunami
- 2011 19th International Euromicro Conference on…
- 2011

With the prevalence of massively parallel computer architecture, MPI parallelization of existing simulation codes for stand-alone system and its parallel optimization to achieve feasible scalability are in critical need. Of many numerical approaches, adaptive mesh refinement(AMR) is known to be one of the particular cases in which MPI parallelization is… (More)

- K. Ida, M. Yoshinuma, +118 authors A. Komori
- 2015

The driving and damping mechanism of plasma flow is an important issue because flow shear has a significant impact on turbulence in a plasma, which determines the transport in the magnetized plasma. Here we report clear evidence of the flow damping due to stochastization of the magnetic field. Abrupt damping of the toroidal flow associated with a transition… (More)

Multiscale gyrokinetic turbulence simulations with the real ion-to-electron mass ratio and β value are realized for the first time, where the β value is given by the ratio of plasma pressure to magnetic pressure and characterizes electromagnetic effects on microinstabilities. Numerical analysis at both the electron scale and the ion scale is used to reveal… (More)

- Shinya Maeyama, Tomohiko Watanabe, Yasuhiro Idomura, Motoki Nakata, Masanori Nunami, Akihiro Ishizawa
- Parallel Computing
- 2015

- Yasuhiro Idomura, Motoki Nakata, +8 authors Naoyuki Shida
- 2012 SC Companion: High Performance Computing…
- 2012

A plasma turbulence research based on 5D gyrokinetic simulations is one of the most critical and demanding issues in fusion science. To pioneer new physics regimes both in problem sizes and in time scales, an improvement of strong scaling is essential. Overlap of computations and communications is a promising approach in improving strong scaling, but it… (More)

- Masanori Nunami
- 2002

Unrenormalizable theories contain infinitely many free parameters. Considering these theories in terms of the Wilsonian renormalization group (RG), we suggest a method for removing this large ambiguity. Our basic assumption is the existence of the maximal ultraviolet cutoff in a cutoff theory, and we require that the theory be so fine-tuned as to reach the… (More)

To achieve a maximal locality in a trivial field theory, we maximize the ultraviolet cutoff of the theory by fine tuning the infrared values of the parameters. This optimization procedure is applied to the scalar theory in D + 1 dimensions (D ≥ 4) with one extra dimension compactified on a circle with radius R. The optimized, infrared values of the… (More)

Plasma turbulence is governed by multi-scale physics, extending over spatio-temporal scales of electrons and ions, whose simulations based on the gyrokinetic theory require huge computations. In this work, we present optimizations of the gyrokinetic Eulerian code GKV, which performs five-dimensional (5D) computational fluid dynamics calculations by means of… (More)