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

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Farewell message from Yuto Yamamoto

Our colleague, Yuto Yamamoto, will be joining the Department of Mathematics, School of Science, Institute of Science Tokyo as an Assistant Professor starting in October 2026. We will all miss him and wish him the best of luck in his new endeavor. Here is a message from Yuto: <i>I am very grateful for the opportunity to have been a member of iTHEMS. During my time here, I enjoyed the stimulating research environment and many opportunities to interact with researchers from different fields.</i> <i>I would like to thank all the members and administrative staff of iTHEMS for their support and for making my time here productive and enjoyable. I have learned a lot from seminars, discussions, and informal conversations with colleagues.</i> <i>Although I am leaving iTHEMS, I hope to stay in touch and to have opportunities to meet and collaborate again in the future. I wish iTHEMS and all its members continued success.</i> <i>Thank you very much for everything.</i>

2026-09-15
Farewell message from Kai Murai

Our colleague, Kai Murai, will be joining Tohoku University as an Assistant Professor starting in October 2026. We will all miss him and wish him the best of luck in his new endeavor. Here is a message from Kai: <i>At the end of September, I will leave iTHEMS and move to Tohoku University as an assistant professor.</i> <i>I joined iTHEMS as an SPDR this April. Although my time here was short, it was a very stimulating experience. I especially appreciated the environment where researchers from various fields worked in the same place. It was interesting to be surrounded by research on topics quite different from my own, and I also enjoyed the opportunities to talk with researchers from other fields.</i> <i>I am very grateful to the iTHEMS members who talked with me, as well as to the assistants for all their support. I will come back to iTHEMS for workshops and other occasions, and I look forward to seeing many of you again.</i>

2026-09-15
JST-ASPIRE Symposium Held in Palo Alto

On July 24, 2026, the JST-ASPIRE Symposium, “Strengthening Japan–U.S. Research Collaboration through International Talent Circulation,” was held at the Japan Innovation Campus in Palo Alto, California. Organized by the Japan Science and Technology Agency (JST), the symposium brought together representatives of the Japanese government, principal investigators of ASPIRE projects, early-career researchers conducting research in the United States, and U.S.-based researchers. The program focused on research activities supported by ASPIRE, the experiences of early-career researchers working abroad, and future opportunities for Japan–U.S. research collaboration. A panel discussion also addressed how international researcher mobility can contribute to strengthening research capabilities and building sustainable international networks. Four young researchers participating in the RIKEN–Berkeley Mathematical Quantum Science Initiative—Yuuka Kanakubo, Gabriele Di Ubaldo, Haruki Emori, and Shoto Aoki—gave a joint presentation. They introduced their respective research activities and shared experiences gained through conducting research in the United States, as well as their perspectives on future research and career development. Their diverse research areas, ranging from high-energy and nuclear physics to quantum gravity, quantum information, and lattice gauge theory, reflect the broad scope of the RIKEN–Berkeley collaboration. The symposium provided an opportunity to introduce the activities of the RIKEN–Berkeley Mathematical Quantum Science Initiative within the broader ASPIRE program and to consider the importance of sustained researcher exchange between Japan and the United States. Reported by Shuntaro Aoki

2026-09-15
Masason Foundation Summer Program Visit to the RIKEN–Berkeley Center on August 11, 2026

Participants in the Masason Foundation’s summer program visited the RIKEN–Berkeley Center at the University of California, Berkeley, on August 11, 2026. The summer program provides young participants with opportunities to broaden their perspectives through visits to universities, research institutions, and other organizations, and through direct interactions with researchers and professionals. The visit began with a tour of the UC Berkeley Physics Department, including an introduction to its history and research environment. This was followed by short presentations by researchers, including Shoto Aoki, Yuka Kanakubo, Gabriele Di Ubaldo, and Akira Dohi, who introduced their research activities to the participants. In the latter part of the program, the participants visited several experimental laboratories at UC Berkeley. Through the presentations, discussions, and laboratory visits, they had an opportunity to learn about a broad range of research activities and to experience firsthand the environment in which cutting-edge research is carried out. The visit provided a valuable opportunity for the young participants to interact directly with researchers at RIKEN and UC Berkeley and to gain a broader perspective on scientific research and possible future career paths. Reported by Shuntaro Aoki

2026-09-08
From Vietnam to Korea: A Summer of Quantum Computing

Duc-Truyen Le, a graduate student at Saitama University, is currently affiliated with iTHEMS as an International Program Associate (IPA). This summer, he participated in a series of quantum computing activities in Vietnam and Korea. In Vietnam, his team received an Honorable Mention at an international quantum computing hackathon involving participants from across Southeast Asia. We asked Duc-Truyen to share his experience with the iTHEMS community: From July 9 to 31, I stayed in Vietnam, mainly to prepare for and participate in a major quantum computing event that brought together scientists, industry leaders, policymakers, and government representatives. The event aimed to strengthen collaboration and promote investment in quantum technologies across both the public and private sectors. The program consisted of a series of activities held over more than a week, including workshops, discussions, networking events, and competitions. One of the highlights was the International Hackathon on Quantum Computing for Social Good (QC4SG Vietnam 2026 / 2nd SEA Quantathon), which brought together participants from across Southeast Asia. The competition was highly selective, with more than 500 initial applications. Selected teams went through a training phase before the finalists were invited to Vietnam to present their projects. For more information about the competition, please see the related link below. Among more than 20 finalist teams, comprising around 100 participants, our team, QuanWatt, was honored to receive an Honorable Mention. It was a rewarding experience and a valuable opportunity to exchange ideas with participants from different backgrounds. Our project explored how quantum computing could contribute to the analysis of modern power systems, which are becoming increasingly complex with the growing integration of renewable energy sources and smart-grid technologies. Although considerable work remains before such approaches can be applied in practice, it was encouraging to see increasing interest from both academia and industry in practical applications of quantum computing. Following the program in Vietnam, I traveled to Korea, where I attended a course at the Institute for Basic Science (IBS) from August 1 to 8 on “Quantum Computing for Quantum Field Theory.” This provided another valuable opportunity to learn about the rapidly developing connections between quantum computing and fundamental physics. Overall, these experiences in Vietnam and Korea were both memorable and intellectually stimulating. I am very grateful for the opportunity to participate and for the continued support I have received from iTHEMS.

2026-09-01
The 3rd NCTS-iTHEMS Joint Workshop on Theoretical, Mathematical, and Computational Sciences on August 18, 2026

The 3rd NCTS-iTHEMS Joint Workshop on Theoretical, Mathematical, and Computational Sciences was held from August 18 to 21, 2026, at the NCTS Physics Lecture Hall in the Cosmology Hall of National Taiwan University (NTU), Taipei. This was the third workshop in the series jointly organized by Taiwan's National Center for Theoretical Sciences (NCTS) and RIKEN iTHEMS, following the first workshop hosted by NCTS in 2024 and the second hosted by RIKEN in 2025. This year's workshop carried special significance as the first major joint activity after the signing ceremony held at NTU on April 23, 2026, where iTHEMS and NCTS launched the joint research initiative "Mathematical Frontiers for Matter, Life, and the Universe." The initiative, signed by iTHEMS Director Satoshi Iso and NCTS Directors Pei-Ming Ho and Ming-Lun Hsieh, aims to foster outstanding early-career researchers and to promote researcher exchanges, international symposia, and collaborative research between the two institutions. Reflecting this spirit, the scope of the workshop expanded beyond previous editions to encompass theoretical physics, mathematics, and computational sciences. The four-day program featured 28 talks and 10 posters. Three plenary lectures were delivered by Tzu-Chieh Wei (Stony Brook University) on the stability of quantum many-body phases against time-dependent perturbations, Etera Livine (ENS Lyon) on spinfoam approaches to quantum gravity, and Tan Bui-Thanh (UT Austin) on model-constrained scientific machine learning for digital twins. Thirteen invited speakers from RIKEN iTHEMS and twelve from Taiwanese universities and Academia Sinica presented research spanning high-energy physics, gravity, condensed matter physics, quantum information and computing, geometry and topology, applied mathematics, machine learning, and scientific AI. In the poster session, ten presenters, mostly students and early-career researchers, introduced their work in three-minute flash talks followed by lively discussions over coffee. The directors of both institutions delivered the opening and closing remarks, and the iTHEMS and NCTS organizers held internal discussions on future joint activities during the workshop. The interdisciplinary atmosphere led to many cross-field conversations during the coffee breaks, the poster session, and the banquet, and several new contacts between researchers of the two institutions were established. We thank the NCTS staff for their excellent local organization and all speakers and participants for making the workshop a success. We look forward to continuing the series and to deepening the collaboration between NCTS and iTHEMS under the new initiative. Reported by Ching-Kai Chiu

2026-08-31
New Mechanism for Sustaining Reputation-Based Cooperation Revealed

An international research team including iTHEMS Team Director Yohsuke Murase has theoretically uncovered a new mechanism that enables the evolution of reputation-based cooperation. In human societies, “indirect reciprocity,” in which people decide whether to cooperate with others based on their reputations, is considered an important mechanism for sustaining cooperation. However, previous studies have shown that maintaining cooperation becomes difficult when individuals hold different assessments of the same person. In this study, the researchers introduced a mechanism called “dual reputation updating,” in which reputations are updated based not only on whether a person cooperates with others, but also on whether that person receives cooperation from others. Through mathematical analysis and computer simulations, they demonstrated that this simple extension reduces disagreements in reputation and substantially enhances the maintenance of cooperation. These findings are expected to deepen our understanding of how cooperation emerges and is sustained through reputation, while also providing new insights into collective behaviors in real-world societies, including conformity, cooperation, and exclusion. The findings are scheduled to be published in the Proceedings of the National Academy of Sciences (PNAS) on August 28, 2026.

2026-08-25
Farewell message from Sungsik Kong

Our colleague, Sungsik Kong, will be joining Sejong University in South Korea as a tenure-track Assistant Professor in September 2026. We will all miss him and wish him every success in this exciting new chapter. Here is a message from Sungsik: <i>I joined iTHEMS in August 2025, and over the past year I have had the privilege of working in an exceptional research environment. Starting in September 2026, I will be joining Sejong University in South Korea as a tenure-track Assistant Professor. While I am excited about this move, I am also sad to be leaving my position as a Research Scientist at iTHEMS.</i> <i>My time at RIKEN has been both challenging and incredibly rewarding. I am deeply grateful to RIKEN and iTHEMS for giving me the opportunity to pursue the scientific questions I am passionate about. I will miss iTHEMS' collaborative atmosphere. I have had the chance to learn from researchers across many different fields, many that I would never have had the opportunity to explore otherwise. Those seminars, colloquiums, and conversations have broadened my perspective, sparked new ideas, and made my time here truly valuable and memorable.</i> <i>If you ever visit Seoul, please don't hesitate to get in touch. Thank you all so much. It has been a real pleasure.</i>

2026-08-17
Using chaos and symmetry to bootstrap quantum gravitational wormholes

An international research collaboration between Gabriele Di Ubaldo (RIKEN-Berkeley Center at UC Berkeley and RIKEN iTHEMS), Jan Boruch (University of California, Berkeley, US), Felix M. Haehl (University of Southampton, UK), Eric Perlmutter (Université Paris-Saclay and Institut des Hautes Études Scientifiques, France), and Moshe Rozali (University of British Columbia, Canada) published the new study in <em>Physical Review Letters</em>. Random matrix theory provides a universal description of chaos in quantum systems, capturing statistical patterns among energy levels without requiring knowledge of microscopic details. The new challenge addressed is its extension to 2D Conformal Field Theories and their holographically dual 3D quantum gravity via the AdS₃/CFT₂ correspondence. In the AdS₃/CFT₂ correspondence, quantum gravity in a three-dimensional negatively curved spacetime is encoded in a two-dimensional conformal field theory on its boundary. The key difference is <strong>modular invariance</strong>, a symmetry stating that a theory on a 2D torus is invariant under modular transformations, which imposes stringent constraints and a rigid mathematical structure, seemingly incompatible with quantum chaos and random matrix theory. Building on the 2023 work of Di Ubaldo and Perlmutter, “AdS₃/RMT₂ duality”, the researchers developed a general, nonperturbative framework called RMT₂ that uplifts the correlations of any random matrix model into fully modular-invariant quantities. The team then used RMT₂ to predict quantum amplitudes for 3D wormholes with multiple torus-shaped boundaries. A wormhole is a tunnel-like geometric connection between otherwise separate regions or boundaries of spacetime. While it is not a shortcut for interstellar travel as in sci-fi movies, it encodes deeply quantum information about gravity and black holes. For the three-boundary wormhole, the team also performed a gravity calculation that agrees with the RMT₂ prediction. By turning the earlier AdS₃/RMT₂ proposal into a general framework, the study advances a research direction that Gabriele helped pioneer and provides a new tool for probing black-hole microstates and, in the near future, solving AdS₃ quantum gravity. For further details, please see the article in <em>Physical Review Letters</em>.

2026-08-07
Riccardo Muolo Awarded Third Place at Falling Walls Lab Tokyo 2026

Riccardo Muolo awarded 3rd Place at Falling Walls Lab Tokyo, Japan Riccardo Muolo (Special Postdoctoral Researcher, Division of Fundamental Mathematical Science, iTHEMS) took part in the Falling Walls Lab Tokyo, Japan, held on 28 July 2026 at Shibuya Sakura Stage, and was awarded 3rd Place by the jury. The Falling Walls Lab is an international pitch and science-communication competition hosted by the Falling Walls Foundation, a Berlin-based non-profit founded in 2009 on the twentieth anniversary of the fall of the Berlin Wall. The Foundation channels the spirit of that night to ask a recurring question — which are the next walls to fall in science and society — and works to make breakthrough ideas accessible across borders and disciplines. Open to students and early-career professionals of all disciplines and nationalities, the Lab invites participants to pitch their research, business model, or innovative idea in just three minutes, in front of their peers and a jury from academia and business. Academic institutions around the world are invited to host their own Falling Walls Lab and send their winners to the Falling Walls Lab Finale in Berlin, where the Finalists compete for the title of Breakthrough Winner in the Emerging Talents category and the chance to pitch again on the main stage of the Falling Walls Science Summit. This year’s Tokyo edition was organized by EURAXESS Japan, the German Centre for Research and Innovation (DWIH) Tokyo, and Tobitate! Japan. Riccardo’s research covers nonlinear dynamics on networks and higher-order structures, synchronization, Turing pattern formation, and the control of dynamical systems — exactly the kind of cross-disciplinary work the Falling Walls Lab is designed to showcase. Distilling it into a compelling three-minute pitch and earning recognition among a strong international field of participants is a fine achievement. Congratulations, Riccardo!

2026-08-07

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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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Visiting

Yang-Yang Tan

Postdoctoral Researcher, Institute for Physics of Intelligence, Graduate School of Science, The University of Tokyo

Term: May 1 (Fri) 2026 - April 30 (Fri) 2027

Visiting Place: Main Research Building, RIKEN Wako Campus
Visiting

Liang Zhang

Visiting Scientist, Quantum Mathematical Science Team, Division of Applied Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) / Postdoctoral Researcher, Institute of Modern Physics, Fudan University, China

Term: September 4 (Fri) - November 3 (Tue) 2026

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

Ph.D. Student, The University of Osaka

Term: September 7 (Mon) - 18 (Fri) 2026

Visiting Place: Main Research Building, RIKEN Wako Campus