News
9 news in 2026
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2026-01-15
Hot Topic
iTHEMS Colloquium by Hiroki R. Ueda on October 10, 2025
On October 10, 2025, Dr. Hiroki Ueda, Professor at the University of Tokyo’s Graduate School of Medicine and former Team Leader at RIKEN Center for Biosystems Dynamics Research (BDR), delivered a splendid iTHEMS Colloquium talk on the Wako campus. His lecture, titled “Why Do We Sleep? The Role of Calcium and Phosphorylation in Sleep,” attracted a wide audience—not only researchers from iTHEMS but also colleagues from other RIKEN centers, including the Pioneering Research Institute (PRI) and the Center for Brain Science (CBS), as well as administrative staff. The talk was highly engaging and accessible to specialists and non-specialists alike. Dr. Ueda began with an overview of the long history of sleep research and the major unsolved questions that continue to inspire the field. He then presented his group’s recent discoveries on the role of calcium in sleep regulation. He also introduced a new theoretical framework—the WISE (Wake Inhibition Sleep Enhancement) mechanism—together with its mathematical modeling. Because sleep is closely connected to our daily lives, the audience had many questions from diverse perspectives, and Dr. Ueda kindly addressed each of them in detail. During and after the colloquium, including at the dinner that followed, we had stimulating discussions with him about his group’s model and potential new directions for sleep research and related areas of life science. We are deeply grateful to Dr. Ueda for his inspiring lecture and for sharing his broad expertise with our community. (Photos: courtesy of Assistant Chikako Ota, RIKEN iTHEMS.) Reported by Gen Kurosawa
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2026-01-15
Press Release
A New Principle for Controlling the “Butterfly Effect”
Takemasa Miyoshi (Team Principal, Data Assimilation Research Team, RIKEN Center for Computational Science (R-CCS) / Team Director, Prediction Science Research Team, Division of Applied Mathematical Science, RIKEN iTHEMS), has developed a new mathematical framework for efficiently controlling chaos by turning the fundamental limitation of predictability in deterministic chaos—widely known as the “butterfly effect”—to an advantage. He proposed a “duality principle,” demonstrating that data assimilation, which forms the foundation of weather forecasting (a process that synchronizes a model with the behavior of nature using observational data), and the control of chaos are mathematically twin concepts. Rather than suppressing chaos itself, this new approach exploits the high sensitivity characteristic of chaotic systems to synchronize real-world behavior with a manageable “target trajectory” through only a small amount of “intervention.” In this way, the study theoretically outlines a path toward controlling chaos beyond the conventional limits of predictability. This achievement provides a theoretical basis for future research in disaster prevention and mitigation—for example, applying minimal interventions to synchronize real atmospheric phenomena with a “typhoon scenario that causes no damage” (a target trajectory) simulated in a model, with the aim of avoiding extreme weather events. It is also expected to have applications in a wide range of fields that exhibit chaotic behavior, including ecosystems and economics. For further details, please refer to the related links.
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2026-01-15
Press Release
A 300-Billion-Particle Milky Way Simulation Achieved with AI × Fugaku
An international collaborative research team including Keiya Hirashima, Special Postdoctoral Researcher, has achieved the world’s highest-resolution simulation of the Milky Way galaxy by utilizing the entire system of the AI and supercomputer “Fugaku” (approximately 150,000 nodes) and modeling 300 billion particles representing stars, interstellar gas, and other components—resolving the galaxy down to individual stars. This research is expected to contribute to a better understanding of the Milky Way’s spiral arm structure (the arm-like features of spiral galaxies that extend outward from the center while winding across the galactic disk), the circulation of chemical elements within the galaxy, and the origins of the materials that formed the Solar System and life. For more details, please refer to the related links.
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2026-01-15
Paper of the WeekWeek 3, January 2026
Title: Equivalence of Doubly Periodic Tangles Author: Ioannis Diamantis, Sofia Lambropoulou, Sonia Mahmoudi arXiv: http://arxiv.org/abs/2310.00822v2 Title: Relaxation Process During Complex Time Evolution In Two-Dimensional Integrable and Chaotic CFTs Author: Chen Bai, Weibo Mao, Masahiro Nozaki, Mao Tian Tan, Xueda Wen arXiv: http://arxiv.org/abs/2601.09290v1 Title: Dissipative ground-state preparation of a quantum spin chain on a trapped-ion quantum computer Author: Kazuhiro Seki, Yuta Kikuchi, Tomoya Hayata, Seiji Yunoki arXiv: http://arxiv.org/abs/2601.08137v1 Title: Coherence of Supermassive Black Hole Binary Demographics with the nHz Stochastic Gravitational Wave Background Author: Katsunori Kusakabe, Yoshiyuki Inoue, Daisuke Toyouchi arXiv: http://arxiv.org/abs/2510.10548v2 Title: Extending the Handover-Iterative VQE to Challenging Strongly Correlated Systems: $N_2$ and Fe-S Cluster Author: Pilsun Yoo, Kyungmin Kim, Eyuel E. Elala, Shane McFarthing, Aidan Pellow, Johanna I. Fuks, Doo Hyung Kang, Pratanphorn Nakliang, Jaewan Kim, Himadri Pathak, Tomonori Shirakawa, Seiji Yunoki, June-Koo Kevin Rhee arXiv: http://arxiv.org/abs/2601.06935v1 Title: Dynamics of Interfaces in the Two-Dimensional Wave-Pinning Model Author: Shunsuke Kobayashi, Koya Sakakibara, Taikei Uechi arXiv: http://arxiv.org/abs/2601.04746v1
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2026-01-08
Hot Topic
RIKEN–IBS Joint Workshop on Mathematical Approaches to Nature Held in Daejeon, Korea, December 9–12, 2025
In December 9–12, 2025, a collaborative workshop jointly organized by the Institute of Basic Science (IBS, Korea) and RIKEN was held in Daejeon, Korea. The workshop aimed to explore the unifying mathematical principles that underlie diverse natural phenomena—from the fundamental interactions that shape the universe to the complex behaviors observed in living systems. From RIKEN, iTHEMS researchers including Derek Inman, Ryo Namba, Alvaro Pastor Gutierrez, Shuntaro Aoki, Sungsik Kong, Amaury Micheli, Puttarak Jai-akson, Ryoko Oishi-Tomiyasu, Che-Yu Chen, and Christy Kelly delivered talks. All the presentations were impressive and thoughtfully prepared so that researchers from different fields could follow and appreciate the content. Indeed, there were many stimulating cross-disciplinary questions, and we enjoyed lively discussions over lunches and dinners, accompanied by excellent (and wonderfully spicy) food. Although the workshop was originally designed to foster collaboration between RIKEN and IBS, connections were already present—for example, through Shuntaro Aoki, a physicist at iTHEMS formerly at IBS, and Shingo Gibo, a mathematical biologist at IBS formerly at iTHEMS. This workshop further strengthened these ties and created new ones. The planning and local organization of the workshop were led by the center of Masahide Yamaguchi (IBS), Yusuke Yamada (IBS), and by Yuto Yamamoto and Ryo Namba at RIKEN iTHEMS, with strong support from IBS and the International Collaboration Section of the Global Strategy Division at RIKEN. We are deeply grateful for their dedicated efforts. I hope that the successful interactions fostered through this workshop will continue to develop even further. (Photos: courtesy of Director Satoshi Iso, RIKEN iTHEMS.) Reported by Gen Kurosawa
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2026-01-08
Paper of the WeekWeek 2, January 2026
Title: Phases of the $q$-deformed $\mathrm{SU}(N)$ Yang-Mills theory at large $N$ Author: Tomoya Hayata, Yoshimasa Hidaka, Hiromasa Watanabe arXiv: http://arxiv.org/abs/2601.03843v1 Title: Revisiting Spherically Symmetric Spacetime I: Geometro-Hydrodynamics Author: Puttarak Jai-akson, Yuki Yokokura arXiv: http://arxiv.org/abs/2601.03077v1 Title: Exceptional Lines and Excitation of (Nearly) Double-Pole Quasinormal Modes: A Semi-Analytic Study in the Nariai Black Hole Author: Nao Nakamoto, Naritaka Oshita arXiv: http://arxiv.org/abs/2601.00704v1 Title: Gauge Symmetry in Quantum Simulation Author: Masanori Hanada, Shunji Matsuura, Andreas Schafer, Jinzhao Sun arXiv: http://arxiv.org/abs/2512.22932v1
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2026-01-08
Seminar Report
GW-EOS WG Seminar by Pierbiagio Pieri on November 6, 2025
In this seminar, pairing phenomena in three kinds of quantum many-body systems were discussed. First, the speaker reviewed his work on the Bose-Fermi mixture, mainly focusing on the quasiparticles called Fermi-polarons. Second, inhomogeneous pairing fluctuations in a spin-polarized Fermi-Fermi mixture are reviewed. Finally, dissipations called mutual friction arising from interplay between Andreev bound states in the vortex core and delocalized thermal excitations were discussed for strongly interacting Fermi superfluids. Reported by Yuta Sekino
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2026-01-06
Award
Yuya Kusuki Receives the 22nd (FY 2025) JSPS Prize
Yuya Kusuki (Visiting Scientist, iTHEMS / Associate Professor, Institute for Advanced Study, Kyushu University) has received the 22nd (Fiscal Year 2025) Japan Society for the Promotion of Science (JSPS) Prize. The JSPS Prize was established to recognize outstanding young researchers with exceptional creativity and research ability at an early stage of their careers, and to support their motivation and further development in research. Kusuki has made significant contributions through his research on the development and application of new methods at the interface between quantum gravity and quantum many-body systems. This award recognizes the originality and academic impact of his research achievements. The award ceremony is scheduled to be held on February 3, 2026, at the Japan Academy Hall. Congratulations, Yuya!
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2026-01-01
Paper of the WeekWeek 1, January 2026
Title: Geometric phase of exceptional point as quantum resonance in complex scaling method Author: Okuto Morikawa, Shoya Ogawa, Soma Onoda arXiv: http://arxiv.org/abs/2512.24528v1 Title: Tensor Computing Interface: An Application-Oriented, Lightweight Interface for Portable High-Performance Tensor Network Applications Author: Rong-Yang Sun, Tomonori Shirakawa, Hidehiko Kohshiro, D. N. Sheng, Seiji Yunoki arXiv: http://arxiv.org/abs/2512.23917v1 Title: Description of Baryon Mass Spectrum by Open Strings and Diquarks Author: Yuki Fujimoto arXiv: http://arxiv.org/abs/2512.24882v1 Title: Measuring out-of-time-order correlators on a quantum computer based on an irreversibility-susceptibility method Author: Haruki Emori, Hiroyasu Tajima arXiv: http://arxiv.org/abs/2512.22643v1 Title: Error and Disturbance as Irreversibility with Applications: Unified Definition, Wigner--Araki--Yanase Theorem and Out-of-Time-Order Correlator Author: Haruki Emori, Hiroyasu Tajima arXiv: http://arxiv.org/abs/2309.14172v3
9 news in 2026