RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) | iTHEMS

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Identifying Topological Superconductors from Fermi Surface Information

An international research group including Seishiro Ono, Special Postdoctoral Researcher, Division of Fundamental Mathematical Science, iTHEMS (at the time of the research; currently Visiting Scientist, Division of Global Collaborations and Research Talent Development), has established a theoretical formula that determines the topological properties of superconductors from information on the “Fermi surface,” which describes the electronic states responsible for electrical conduction and superconductivity. These research results are expected to provide a foundation for efficiently searching for topological superconductors among a vast number of materials, thereby accelerating both theoretical predictions and experimental exploration of candidate materials. For more details, please see the RIKEN press release.

2026-05-26
Discovery of a New Phenomenon Where Translational Symmetry Can No Longer Be Restored

A research group consisting of Tsubasa Oishi and doctoral student Takuma Saito of the Yukawa Institute for Theoretical Physics, Kyoto University, and Hiromi Ebisu, Research Scientist at RIKEN, has revealed that in systems of arbitrary dimensions subject to the Lieb–Schultz–Mattis (LSM) constraint arising from the interplay between internal symmetry and translational symmetry, the operation known as gauging—which converts a global symmetry into a local one—causes the translational symmetry itself to transform into a non-invertible symmetry. For further details, please see the Kyoto University press release.

2026-05-25
Mayor Takeshi Sakamoto of Itabashi City Visits iTHEMS on May 14

On May 14, Takeshi Sakamoto, Mayor of Itabashi City, visited iTHEMS and met with Center Director Satoshi Iso. Mayor Sakamoto introduced Itabashi City’s initiatives and basic development plan, followed by Director Iso’s presentation on the vision and activities of iTHEMS. The mayor then toured the iTHEMS spaces on the 2nd to 4th floors of the east side of the Main Research Building, where he interacted with researchers engaged in active discussions. In addition, at the Memorial Archives Room, Mayor Sakamoto viewed valuable historical materials that are also connected to Itabashi City.

2026-05-18
Talk Event “Useless Science and Art vol.2” Held at the Museum of Contemporary Art Tokyo

As a related event to the exhibition MOT Collection: Mission∞Infinity – Space × Art × Quantum, currently being held at the Museum of Contemporary Art Tokyo, the talk event “Useless Science and Art vol.2: Prototyping ‘Useless’ Science and Art” took place on Wednesday, May 6, 2026. This event was organized in connection with Black Hole Recorder, a work inspired by quantum black hole theory. Researchers and creators gathered to discuss the new possibilities that can emerge from ideas that may initially appear “useless.” Approximately 110 people attended the event. During the talks, the speakers introduced the conceptual framework of Black Hole Recorder and the theoretical ideas behind its creation. Visitors were also able to experience part of the work through a listening session held at the venue. The speakers included Tetsuo Hatsuda (Team Director, Quantum Mathematical Science Team, RIKEN iTHEMS), Koji Hashimoto (Professor, Graduate School of Science, Kyoto University), Yoshihiro Kozuka (Creative Director, ADK Marketing Solutions), and Haruka Kodama (Experience Designer, ADK Marketing Solutions). From their respective professional perspectives, they exchanged ideas on collaborations between science and art. Professor Hashimoto also discussed his cross-disciplinary activities exploring the theme of “Quantum × Music,” including translating concepts from quantum physics into musical expression. This program was held as the second installment of an ongoing talk series. Following the first session, the discussion further explored the significance of initiatives that bridge academic research and creative practice. After the main event, a wrap-up talk featuring participating artists, creators, and researchers from the exhibition was also held, with the same members continuing the discussion.

2026-05-18
iTHEMS x academist Online Event "World of Mathematical Sciences 2026" on April 18, 2026

RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) held the online event “Exploring the World of Science through Mathematics 2026” on Saturday, April 18, 2026, in collaboration with academist Inc. The event featured a series of lectures spanning a wide range of scientific fields, all connected through the perspective of mathematical sciences. Junnosuke Koizumi, Osamu Fukushima, Muzi Hong, and Kenji Okubo each gave presentations in their respective areas of expertise. The talks incorporated concrete examples to facilitate understanding, and also included discussions with commentators as well as Q&A sessions with participants. In addition, during the lunch break, Honorary Research Scientist Shun-ichi Amari and iTHEMS Director Satoshi Iso led a special session titled “Intelligence and Learning in the Age of AI.” Through an interactive dialogue with practical examples, they discussed how AI is influencing human intellectual activity and transforming approaches to learning. According to the post-event survey, overall satisfaction with the event was high. While some participants commented that the presentations were “somewhat difficult,” many also described them as “easy to understand.” A total of 303 participants (528 cumulative attendees) joined the event, with the maximum number of simultaneous connections reaching 184.

2026-05-14
Mathematical Genomics ECL Research Unit Retreat, 27–28 April 2026

On 27 - 28 April, the Mathematical Genomics ECL Research Unit went on a two-day retreat to SUURI-COOL Kyoto. With two new members joining in April, the retreat was a great chance for everyone to get together outside our usual work environment. Our unit started in late 2024 and over the past year and a half, we have grown to six members: Leo Speidel, Unit Leader, Lucas Sort and Aina Colomer i Vilaplana, both postdocs who joined last year, Tomoko Iwanami who is our most valued assistant, and most recently, we welcomed two additional members to our unit, postdoctoral scientist Alba Nieto Heredia and PhD student Satsuki Hirasawa. As a team, our expertise lies in modelling how our genomes are inherited through generations and using statistical inference to uncover the stories hidden within them. Our DNA can tell detailed stories about human history and prehistory, including migration, adaptation, and the origins of modern humans, while also uncovering the biological processes that shape evolution and influence human health today. We decipher these from the genomes of many thousands of present-day people, as well as from DNA sequenced from ancient human bone. The signatures left in our DNA are often subtle but preserve the stories of ordinary people not necessarily recorded in history books. At the retreat, we explored topics beyond our usual day-to-day activities. We organised three sessions: first, a mock Kakenhi grant exercise where each of us pitched a potential research idea; second, a series of practical tutorials on techniques we use in our day-to-day work, including figure design (Aina), AI tools in VS Code (Alba), LaTeX (Lucas), ancient DNA sequencing (Satsuki), and the many quirks of administration (Tomoko); and finally, a deep dive into Japanese history, spanning from prehistoric Japan, the rise of early states, through the world of Heian-period court culture, and all the way up to the Edo period. Attached is a photo of us at Byodo-in Temple in Uji, Kyoto, one of the oldest surviving temple complexes of the Heian period in Japan, already celebrated in classical literature written more than 1,000 years ago.

2026-05-11
RIKEN iTHEMS and Taiwan’s NCTS Launch Joint Research Initiative to Foster Outstanding Early-Career Researchers, Hold Signing Ceremony

In April 2026, the RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) and the National Center for Theoretical Sciences (NCTS) in Taiwan launched a joint research initiative titled “Mathematical Frontiers for Matter, Life, and the Universe,” which aims to address fundamental questions in matter, life, the universe, and society through interdisciplinary approaches centered on mathematics. A signing ceremony was held on April 23 at National Taiwan University (NTU). Representing RIKEN at the ceremony were Satoshi Iso (Director, iTHEMS), Shigehiro Nagataki (Deputy Director, iTHEMS; Division Director, Division of Global Collaborations and Research Talent Development), Yasuyuki Kawahigashi (Deputy Director, iTHEMS), and Tomoya Nagai (Coordinator, iTHEMS). Participants from National Taiwan University (NTU) included Chih-Hsing Yang (Executive Vice President, NTU), Chung-Chih Wu (Vice President for Research and Development (R&D), NTU), Pei-Ming Ho (Director, NCTS), and Ming-Lun Hsieh (Director, NCTS), along with theoretical researchers in physics, mathematics, and related scientific fields from multiple institutions. Through this collaboration, the two institutions aim to further strengthen their partnership by expanding researcher exchanges, co-organizing international symposia, and promoting international collaborative research in cutting-edge theoretical sciences. In addition, this partnership seeks to provide early-career theoretical researchers with an environment that offers a high degree of academic freedom, while creating valuable opportunities to collaborate with researchers across a broad range of disciplines and interdisciplinary fields within Asia’s leading theoretical physics and mathematics communities.

2026-05-11
Takumi Doi Receives the Awards for Science and Technology (Research Category) in the FY2026 Commendation for Science and Technology by MEXT

Takumi Doi (Senior Research Scientist, iTHEMS) has received the Awards for Science and Technology (Research Category) in the FY2026 Commendation for Science and Technology by MEXT. This award is given to researchers who have achieved outstanding research accomplishments. He was honored for his research entitled “ First-Principles Studies of Realistic Hadron Interactions and Exotic Hadrons.” Congratulations, Takumi!

2026-04-30
Farewell message from Iao-Fai Io

Our colleague, Iao-Fai Io, will be returning to National Taiwan University starting in May to complete his Ph.D. We will miss him and wish him all the best in his future career. Here is a message from Iao-Fai: <i>I joined iTHEMS in May 2025 as an International Program Associate (IPA). Over the past year, I have been very happy to be part of the iTHEMS member.</i> <i>RIKEN is one of national research institute in Japan, during my time here I had the opportunity to attend many high-quality seminars and workshops. I have also had the opportunity to visit and interact with member from different centers in RIKEN(such as CEMS, FQSP, RQC, etc.). I am also very grateful for the “coffee meetings” and “iTHEMS Now & Next” events, which helped me understand iTHEMS and learn about research which is beyond my own field.</i> <i>I would like to express my sincere gratitude to my host researcher, Dr. Ching-Kai Chiu. He has taught me a great deal about research, particularly in superconductivity and altermagnetism, which has significantly improved my research abilities in condensed matter theory. Whenever I encountered difficulties in my research, he was always willing to discuss them with me and suggest valuable advice. I am also grateful to him for introducing me his collaborators, including Congcong Le (a former iTHEMS member) and collaborators from China. In addition, I would like to thank him for his support during my visits abroad.</i> <i>I would also like to thank Tomoko Iwanami-san and Chikako Ota-san for their administrative support. In addition, I am grateful to all the people I have met at iTHEMS over the past year (such as Yan, Xiaoyang, Duc-Truyen, Tianyin, Zhe, Jinyang, Rumi, Yuta, Brian, Shuntaro, Lingxiao, Muzi, Sho, Satsuki, Iso, Haruki, Tada, Hatsuda, etc.).</i> <i>Over the coming year, I will return to National Taiwan University to complete my Ph.D., while also beginning to apply for postdoctoral positions. In the future, if I have the opportunity, I would be happy to visit RIKEN iTHEMS again. I sincerely hope to see you all again in the near future.</i>

2026-04-30
Ryusuke Hamazaki Receives the Young Scientists’ Award from MEXT

Ryusuke Hamazaki (RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team, RIKEN Cluster for Pioneering Research (CPR) / Senior Research Scientist, iTHEMS) has received the Young Scientists’ Award in the FY2026 Commendation for Science and Technology by MEXT. This award recognizes early-career researchers who have achieved outstanding research accomplishments. He was honored for his research entitled “Studies on universality and novel phases in nonequilibrium quantum many-body systems.” Congratulations, Ryusuke!

2026-04-27

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RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) is an international research center at RIKEN. It facilitates close collaborations among researchers from different disciplines in theoretical, mathematical and computational sciences. On April 1, 2025, iTHEMS transitioned from a program to a center. The ultimate goal of iTHEMS is to unravel the mystery of the Universe, matter, and life, as well as to solve key problems in modern society through interdisciplinary approaches.

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Director: Satoshi Iso

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Harunobu Fujimura

Ph.D. Student, The University of Osaka

Term: May 11 (Mon) - 27 (Wed) 2026

Visiting Place: Main Research Building, RIKEN Wako Campus
Harunobu Fujimura

Ph.D. Student, The University of Osaka

Term: June 1 (Mon) - 5 (Fri) 2026

Visiting Place: Main Research Building, RIKEN Wako Campus