News
83 news in 2026
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2026-07-30
Paper of the WeekWeek 5, July 2026
Title: $\mathrm{SL}(2,\mathbb{Z})$ Theta Subgroup Structure of Maxwell theory in the Lattice Villain Hamiltonian Formulation Author: Shoto Aoki, Yoshio Kikukawa, Toshinari Takemoto arXiv: http://arxiv.org/abs/2607.25332v1 Title: A Path Integral Model of Cognition Author: Haruki Emori, Kazunori Kondo, Atsushi Iriki, Andrei Khrennikov arXiv: http://arxiv.org/abs/2607.24807v1 Title: Universality of dual mass-scaled fundamental modes in two-fluid neutron stars with mirror dark matter Author: Hajime Sotani, Ankit Kumar arXiv: http://arxiv.org/abs/2607.27005v1 Title: Expected number density of critical points of smooth Gaussian random fields in arbitrary dimensions Author: Satoshi Kuriki, Takahiko Matsubara, Satoshi Iso arXiv: http://arxiv.org/abs/2607.23903v1 Title: Page transition for the complexity of an evaporating black hole Author: Violet Concepcion, Yasunori Nomura, Kyle Ritchie, Samuel Weiss arXiv: http://arxiv.org/abs/2607.21734v1 Title: Continuous solutions of the complex Kac--Bernstein functional equation on the integers and the real numbers Author: Takashi Satomi arXiv: http://arxiv.org/abs/2607.24033v1 Title: On the Nucleon Effective Mass in Neutron Stars Cooling Author: Yuuki Sugiyama, Akira Dohi arXiv: http://arxiv.org/abs/2607.23253v1 Title: A lower bound on primordial power spectrum from halo substructure Author: Shin'ichiro Ando, Nagisa Hiroshima, Koji Ishiwata, Tomo Takahashi arXiv: http://arxiv.org/abs/2607.20884v1 Title: Stochastic Quantization as Optimal Control Author: Lingxiao Wang arXiv: http://arxiv.org/abs/2607.21436v1 Title: Unitary $k$-designs without Hamiltonian quenches Author: Pratik Nandy arXiv: http://arxiv.org/abs/2607.20640v1
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2026-07-29
Hot Topic
2026 iTHEMS Visit by the National Sun Yat-sen University, Taiwan
On June 25, a group of 3 professors and 13 students from National Sun Yat-sen University, Taiwan, visited RIKEN . The purpose of the visit was to immerse the students in RIKEN’s multidisciplinary research environment and introduce them to stateoftheart scientific methodologies. It also aimed to inspire their future research careers while exploring opportunities for academic exchange and longterm collaboration between both institutions. First, the group visited RIKEN Nishina Center for Accelerator-Based Science, hosted by Dr Claudio Santonastaso & Dr Seiya Sakai. Next visit was RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), hosted by Dr. Gen Kurosawa. Last visit was RIKEN Center for Quantum Computing, hosted by Dr. Franco Nori. Gen Kurosawa, Senior Research Scientist, introduced iTHEMS’s interdisciplinary research environment and explained how mathematical methods from physics can be applied to important questions in biological clocks, leading to testable predictions that are verified experimentally.
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2026-07-24
Hot Topic
Farewell message from Puttarak Jai-akson
Our colleague, Puttarak Jai-akson, will be joining the Graduate School of Science, Kyoto University, as a Program-Specific Researcher, starting in August 2026. We will all miss him and wish him every success in this exciting new chapter. Here is a message from Puttarak: I would like to share that I will be leaving my position as a Postdoctoral Researcher at iTHEMS. I joined iTHEMS in November 2022, and after nearly four wonderful years, I will be moving to a new position as a Researcher at Kyoto University, starting in August 2026. During my time at iTHEMS, I greatly enjoyed the open, friendly, and interdisciplinary research environment. The opportunity to interact with researchers from diverse fields has broadened my perspective, inspired many new ideas, and significantly enriched my research. I am deeply grateful to all the members of iTHEMS for their support, encouragement, and the many enjoyable discussions we have shared. I would also like to express my heartfelt thanks to our wonderful iTHEMS Assistants, whose kindness, professionalism, and constant support made my time at iTHEMS all the more enjoyable. Although I am leaving my full-time position, I am pleased to continue my affiliation with iTHEMS as a Visiting Scientist. I sincerely hope to continue our discussions and collaborations in the future. If you happen to visit Kyoto University, please don't hesitate to let me know. I would be very happy to catch up and continue our conversations. Thank you all very much for everything. It has been a privilege to be part of iTHEMS, and I wish everyone continued success.
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2026-07-23
Paper of the WeekWeek 4, July 2026
Title: Interacting Dark Energy and Dark Matter in O(3) No-Scale Gravity Author: Lincoln da S. Pereira, Muzi Hong, Elisa G. M. Ferreira, Tsutomu T. Yanagida arXiv: http://arxiv.org/abs/2607.20320v1 Title: Gravitational waves from self-resonance during reheating with a quantum-corrected inflaton potential Author: Tomoya Inada, Noel Jonathan Jobu, Kenji Nishiwaki, Toshifumi Noumi, Naoki Yamatsu arXiv: http://arxiv.org/abs/2607.18381v1
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2026-07-16
Paper of the WeekWeek 3, July 2026
Title: Isometries between C$^*$-algebras with finite corank Author: Michiya Mori arXiv: http://arxiv.org/abs/2607.13367v1 Title: Strong-to-Weak Spontaneous Symmetry Breaking from Wormholes in Holography Author: Taishi Kawamoto, Kenya Tasuki, Masahito Yamazaki arXiv: http://arxiv.org/abs/2607.12022v1 Title: Evading Cosmological Strong Coupling in Non-minimally Coupled Vector Gravity Author: Antonio De Felice, Seishi Enomoto, Nagisa Hiroshima, Atsushi Naruko arXiv: http://arxiv.org/abs/2607.11125v1 Title: Magnitude homology of tope graphs Author: Junnosuke Koizumi arXiv: http://arxiv.org/abs/2607.11863v1 Title: Catalog of Altermagnetism in Magnetic Wallpaper/Space Groups and Nonsymmorphic Altermagnets Author: Congcong Le, Fan Cui, Iao-Fai Io, Moritz Hirschmann, Xianxin Wu, Ching-Kai Chiu arXiv: http://arxiv.org/abs/2607.10857v1 Title: Quantum Logic as the Logic of Contexts Author: Haruki Emori, Atsushi Iriki, Andrei Khrennikov, Kazunori Kondo arXiv: http://arxiv.org/abs/2607.09032v1 Title: Solving models with generalized free fermions I: Algebras and eigenstates Author: Kohei Fukai, Balázs Pozsgay, István Vona arXiv: http://arxiv.org/abs/2602.03431v1 Title: A free fermions in disguise model with claws Author: Kohei Fukai, István Vona, Balázs Pozsgay Journal Reference: SciPost Phys. 21, 011 (2026) doi: https://doi.org/10.21468/SciPostPhys.21.1.011 arXiv: http://arxiv.org/abs/2508.05789v2 Title: Diffusion Models for Sampling Near Criticality in Lattice Field Theories Author: Yang-yang Tan, Gert Aarts, Diaa E. Habibi, Biagio Lucini, Lingxiao Wang arXiv: http://arxiv.org/abs/2607.08505v1 Title: Nuclear Many-Body Systems as Benchmarks for Quantum Computing Author: Sota Yoshida, Alessandro Baroni, Takayuki Miyagi, Ermal Rrapaj arXiv: http://arxiv.org/abs/2607.08047v1
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2026-07-16
Hot Topic
2026 iTHEMS Visit by the University of California San Diego Global Seminar Program
On July 8, Dr. Stanley Lo, Teaching Professor in the Department of Cell and Developmental Biology at the School of Biological Sciences, UCSD, visited iTHEMS together with 24 undergraduate students. The purpose of the visit was to learn about iTHEMS and its research activities while supporting the students’ learning about human diversity and the relationship between science and society. Thomas Hitchcock, Research Scientist at iTHEMS, hosted the lecture. He introduced his academic and professional background and presented his current research on evolution, ecology, and genetics.
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2026-07-09
Paper of the WeekWeek 2, July 2026
Title: Strong Evidence for Three-$α$ Clustering in the Ground State of $^{12}\mathrm{C}$ Author: Kazuki Yoshida, Masaaki Kimura arXiv: http://arxiv.org/abs/2606.31437v1 Title: 6d Supergravity Blocks Author: Yuta Hamada, Seongmin Jeon, Hee-Cheol Kim arXiv: http://arxiv.org/abs/2607.05496v1 Title: Equation of state of QCD(-like) theory using Lattice Monte Carlo simulations Author: Etsuko Itou arXiv: http://arxiv.org/abs/2607.04624v1 Title: Quiver BPS Indices from Crystal Profiles Author: Jiakang Bao, Masahito Yamazaki arXiv: http://arxiv.org/abs/2607.03617v1 Title: Lattice study of primordial black hole formation in bumpy axion inflation Author: Masahiro Kawasaki, Kai Murai, Shunsuke Tsuchida arXiv: http://arxiv.org/abs/2607.01780v1
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2026-07-02
Paper of the WeekWeek 1, July 2026
Title: Three-Dimensional Simulations of Type Ia Supernova Remnants I: Effects of a Main-Sequence Companion Star Author: Jingxiao Luo, Gilles Ferrand, Zhengwei Liu, Xuefei Chen, Zhanwen Han Journal Reference: ApJ, 1005, 117 (2026) doi: https://doi.org/10.3847/1538-4357/ae6ce6 arXiv: http://arxiv.org/abs/2607.00354v1 Title: Rethinking quantum information in gravity and fields Author: Kanato Goto, Yuta Hamada, Kohtaro Kato, Takato Mori, Yoshifumi Nakata, Masataka Watanabe, Hayata Yamasaki, Masahito Yamazaki, Takuya Yoda arXiv: http://arxiv.org/abs/2606.30853v1 Title: Analytic index theory and spectral flow in real Hilbert $C^*$-modules Author: Chris Bourne, Alan L. Carey, Koen van den Dungen, Adam Rennie arXiv: http://arxiv.org/abs/2606.31322v1 Title: FRG analysis of dense two-color QCD within the linear sigma model Author: Gergely Fejős, Daiki Suenaga arXiv: http://arxiv.org/abs/2606.31040v1 Title: Nonequilibrium Andreev transport at the QGP-2SC interface Author: Tingyu Zhang, Honoka Hoshino, Hiroyuki Tajima, Motoi Tachibana, Mariusz Sadzikowski arXiv: http://arxiv.org/abs/2606.30521v1 Title: Characterisation of reactive Nash equilibria in repeated additive games Author: Franziska Lesigang, Christian Hilbe, Nikoleta E. Glynatsi arXiv: http://arxiv.org/abs/2606.27653v1 Title: Simultaneous Estimation of Partial-Transpose Moments with Active Memory Independent of the Moment Order Author: Junxiang Huang, Xiaoyang Wang, Xiao Yuan, Yukun Zhang arXiv: http://arxiv.org/abs/2606.14204v2
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2026-06-25
Paper of the WeekWeek 4, June 2026
Title: Time-dependent weighted directed networks of cryptocurrency interaction from high-frequency returns Author: Shubhangam Shukla, Mahesh Peyyala, Abhijit Chakraborty arXiv: http://arxiv.org/abs/2606.25466v1 Title: Time-reversal symmetric topological superconductivity in Machida-Shibata lattices Author: Ioannis Ioannidis, Ching-Kai Chiu, Thore Posske arXiv: http://arxiv.org/abs/2504.08674v2 Title: Neutrinoless double $β$ decay and leptogenesis in seesaw model Author: Kazuo Fujikawa arXiv: http://arxiv.org/abs/2606.24109v1 Title: Conformal blocks, parenthesized braid operad, and $c=1/2$ Virasoro vertex operator algebra Author: Yuto Moriwaki arXiv: http://arxiv.org/abs/2606.23076v1 Title: Microscopic mechanism of the Fayans pairing for the enhancement of charge radii Author: Tomoya Naito, Gianluca Colò, Xavier Roca-Maza, Hiroyuki Sagawa, Enrico Vigezzi arXiv: http://arxiv.org/abs/2606.21491v1 Title: Mechanistic mathematical model of the in vitro infection dynamics of Bunyamwera and Batai viruses including MOI-dependent shortening of the eclipse phase Author: Bevelynn Whaler, Eleanor Todd, Amelia B. Shaw, John N. Barr, Catherine A. A. Beauchemin, Grant Lythe, Carmen Molina-Paris, Martin Lopez-Garcia arXiv: http://arxiv.org/abs/2606.21481v1 Title: Quantum Simulation of Generalized Parton Distributions in the Schwinger Model Author: Tianyin Li, Hongxi Xing arXiv: http://arxiv.org/abs/2606.22602v1 Title: Macroscopic Black-Hole Remnants in a Nonlocal Field Theory: Towards Hawking Radiation in SFT Author: Feng-Yin Cheng, Pei-Ming Ho, Wei-Hsiang Shao arXiv: http://arxiv.org/abs/2606.20314v1
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2026-06-24
Press Release
Tracing the Origin of the “Freely Chosen Numbers” Appearing in the Laws of Nature
An international research team including Yuya Kusuki, Visiting Scientist at iTHEMS (Associate Professor, Institute for Advanced Study, Kyushu University), analyzed a situation in which two conformal field theories are connected through an interface. The researchers showed that, by appropriately extracting the response to a small deformation of the interface, one can obtain a local operator that captures the difference between the two theories. They also provided an explicit method for constructing such operators. This result lends support to the conjecture that quantum gravity does not admit continuous parameters that can be freely chosen from the outside, and is expected to contribute to a deeper understanding of fundamental issues in quantum gravity. For further details, please see the press release from Kyushu University.
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2026-06-18
Paper of the WeekWeek 3, June 2026
Title: Holographic Schwinger-Keldysh effective action for heavy quarks in confinement and deconfinement phases Author: Shin Nakamura, Daichi Takeda arXiv: http://arxiv.org/abs/2606.17919v1 Title: A Lindbladian for holographic Brownian motion Author: Daichi Takeda arXiv: http://arxiv.org/abs/2606.17909v1 Title: Structural Oscillatority Criterion of Boolean Networks Author: Hiroki Kodama arXiv: http://arxiv.org/abs/2606.15852v1 Title: Non-Archimedean balanced metrics and their application to totally degenerate abelian varieties Author: Keita Goto arXiv: http://arxiv.org/abs/2606.15758v1 Title: Hadronic tensor in lattice gauge theories by quantum computing Author: Dairui Zou, Tianyin Li, Jian Liang, Enke Wang, Hongxi Xing arXiv: http://arxiv.org/abs/2606.17003v1 Title: Hadron spectra of finite-density QC$_2$D Author: Kei Iida, Etsuko Itou, Kotaro Murakami, Daiki Suenaga arXiv: http://arxiv.org/abs/2606.13974v1 Title: Invariants of Sequential Circuits and Generalized Non-Abelian Statistics Author: Shintaro Sato, Yoshimasa Hidaka, Ryohei Kobayashi arXiv: http://arxiv.org/abs/2606.11527v1 Title: Numerical Hints for Dyon Condensation at $θ=2π$ via Wilson-'t Hooft Loops in $SU(2)$ Yang-Mills Theory Author: Hiromasa Watanabe, Issaku Kanamori, Okuto Morikawa, Yuki Nagai, Yuya Tanizaki, Akio Tomiya arXiv: http://arxiv.org/abs/2606.13428v1 Title: A model of local and global reciprocity Author: Mari Kawakatsu, Yohsuke Murase, Taylor A. Kessinger, Joshua B. Plotkin arXiv: http://arxiv.org/abs/2606.13678v2
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2026-06-11
Paper of the WeekWeek 2, June 2026
Title: Collective neutrino oscillations: Many-body non-forward effects and non-classicality Author: Julien Froustey, Ermal Rrapaj, Yuhao Liu, Gushu Li, Costin Iancu, Vincenzo Cirigliano arXiv: http://arxiv.org/abs/2606.12404v1 Title: Searches for GeV-Scale ALPs at RHIC Author: Kaori Fuyuto, Claudio Andrea Manzari, Hitoshi Murayama arXiv: http://arxiv.org/abs/2606.07739v1 Title: Post-Merger Gravitational-Wave Uncertainties of Binary Neutron Stars under Multi-Messenger EOS Constraints Author: Yong-Jia Huang, Luca Baiotti arXiv: http://arxiv.org/abs/2606.08522v2 Title: Generative Criticality in Large Language Model Temperature Scaling Author: Huajian Ruan, Jinyang Li, Xingyu Guo, Lingxiao Wang arXiv: http://arxiv.org/abs/2606.06238v1 Title: Magnetic Symmetries and the Structure of Correlation Functions in Quantum Field Theory Author: Masaru Hongo, Kentaro Nishimura arXiv: http://arxiv.org/abs/2606.03082v1 Title: Understanding deconfined quantum critical points from crystalline categorical Landau paradigm Author: Hiromi Ebisu, Bo Han, Weiguang Cao arXiv: http://arxiv.org/abs/2606.05856v1 Title: Symmetry-based selection rules for higher-order interactions in coupled oscillators Author: Iván Léon, Riccardo Muolo, Yuanzhao Zhang, Maxime Lucas arXiv: http://arxiv.org/abs/2606.04904v1
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2026-06-11
Hot Topic
The First RIKEN Quantum International Workshop on Frontiers of Quantum Computing Applications and Quantum-HPC Integration on May 25-26, 2026
The First RIKEN Quantum International Workshop on Frontiers of Quantum Computing Applications and Quantum–HPC Integration was held from May 25 to 26 at the Large Conference Room on the 2nd floor of the Administrative Headquarters, RIKEN Wako Campus. The workshop featured an entirely invited program, consisting of 13 plenary presentations (40 minutes each) and 9 highlight presentations (20 minutes each). The presentations covered a broad range of fields—including quantum chemistry, life sciences, condensed matter physics, atomic physics, and high-energy physics—with a primary focus on the theme of quantum–HPC hybrid integration. With more than 130 registered participants, each presentation was followed by lively and engaging discussions. Furthermore, the networking reception held on the evening of the first day was well-attended, fostering active interaction and collaboration among researchers from universities, national research institutes, and private industries. This workshop is expected to drive further advancements in quantum computing through quantum–HPC hybrid integration. Reported by Shinichiro Fujii
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2026-06-08
Seminar Report
iTHEMS Math Seminar by Mikhail Khovanov on May 28, 2026
On May 28, 2026, iTHEMS hosted a special iTHEMS Math Seminar, “Introduction to Categorification and Link Homology,” delivered by Professor Mikhail Khovanov of Johns Hopkins University. The event was held in a hybrid format at Okochi Hall and via Zoom, with more than 80 participants attending in person and over 70 joining online. Professor Khovanov is a leading mathematician whose work has had a major influence on knot theory, low-dimensional topology, representation theory, and mathematical physics. He is especially well known for introducing the categorification of the Jones polynomial, now called "Khovanov homology". In the talk, Professor Khovanov introduced the idea of “categorification” by starting from the classical relationship between the Euler characteristic and homology groups in topology. He then discussed the Jones polynomial, a knot invariant introduced by mathematician V. F. Jones in the 1980s, with particular emphasis on its representation-theoretic interpretation. He explained how this invariant can be lifted to a homology theory, guiding the audience toward the construction of Khovanov homology. He concluded the talk by mentioning future directions of the theory, including its connections to algebraic geometry and geometric representation theory. Reported by Taketo Sano
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2026-06-04
Paper of the WeekWeek 1, June 2026
Title: Noise spectroscopy of two-body loss as a probe of dynamical bulk viscosity in ultracold atomic gases Author: Tingyu Zhang, Hiroyuki Tajima, Takeo Kato arXiv: http://arxiv.org/abs/2606.01835v1 Title: Equivalence of additive and parametric pinning control protocols for systems of weakly coupled oscillators Author: Riccardo Muolo, Yuzuru Kato Journal Reference: 2026 SICE International Symposium on Control Systems (SICE ISCS) doi: https://doi.org/10.23919/SICEISCS67856.2026.11524551 Title: Solving models with generalized free fermions II: Path-product expansion and conserved charges Author: Kohei Fukai, Balázs Pozsgay, István Vona arXiv: http://arxiv.org/abs/2605.31453v1
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2026-06-03
Award
Keiya Hirashima Receives the HPCI Software Award (Development Division Excellence Award)
Keiya Hirashima, Special Postdoctoral Researcher at the RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), has received the Excellence Award in the Development Division of the HPCI Software Award, presented by the HPCI Consortium. The HPCI Software Award recognizes young researchers and organizations that have made significant contributions to the advancement of computational science through the development and dissemination of useful software. The Development Division specifically honors software that has demonstrated outstanding value in large-scale computational science and related fields. Hirashima received the award for the development of ASURA-FDPS-ML, a galaxy simulation code that incorporates artificial intelligence technologies. The software combines numerical simulations of galaxy formation and evolution with machine learning techniques, aiming to improve the efficiency and capability of large-scale astrophysical simulations. This award recognizes the significance of integrating computational science and AI technologies to advance next-generation scientific computing. Congratulations, Keiya!
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2026-06-03
Award
Okuto Morikawa Receives the 21st Particle Physics Medal: Young Scientist Award
Okuto Morikawa, Special Postdoctoral Researcher at the RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), has been awarded the 21st Particle Physics Medal: Young Scientist Award (FY2026). This award is presented to young researchers who have made outstanding contributions to the field of theoretical particle physics. The award-winning paper established a unified framework based on the exact WKB method for analyzing resonant states, which play an important role in quantum mechanics and quantum field theory. By connecting several previously independent approaches, including Zel'dovich regularization, the complex-scaling method, and the rigged Hilbert space formulation, the work provides a unified perspective on the description of resonant states. The study further demonstrated the effectiveness of this framework through exactly solvable models and was highly recognized for offering new insights that bridge scattering theory, non-Hermitian quantum systems, and resurgence theory. This research advances the fundamental understanding of quantum theories involving resonant states and is expected to contribute to future studies of non-perturbative structures in more general quantum systems, quantum field theories, and quantum gravity. Congratulations, Okuto!
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2026-06-02
Press Release
Development and Safety Validation of a High-Performance Japanese Medical LLM
As part of NEDO’s project “Safety Verification and Demonstration for the Social Implementation of a Japanese Medical Domain-Specific LLM,” a collaborative research team comprising ten institutions, including the University of Tokyo, RIKEN, and Kyushu University, developed a high-performance Japanese large language model (LLM) designed to support administrative tasks in healthcare settings. In evaluations based on specialist medical examinations, the model achieved an accuracy of up to 90.8%, demonstrating performance comparable to state-of-the-art commercial LLMs. The project also conducted extensive safety assessments tailored to the characteristics of the Japanese healthcare system. Jun Seita, Team Director of the Medical Science Deep Learning Team at iTHEMS, also participated in the project and contributed to its research and development. For more details, please see the NEDO press release.
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2026-05-28
Paper of the WeekWeek 5, May 2026
Title: Revisiting boundary electromagnetic duality and edge modes Author: Keito Shimizu, Sotaro Sugishita arXiv: http://arxiv.org/abs/2605.27870v1 Title: Estimation of potential radius based on momentum distribution of a constituent particle Author: Eisuke Kawamura, Kotaro Murakami, Daisuke Jido arXiv: http://arxiv.org/abs/2605.28323v1 Title: Fermionic Bubble Loop in Cosmological Collider Revisited: Exact signals from spectral and Mellin-Barnes methods Author: Shuntaro Aoki, Zhehan Qin, Masahide Yamaguchi, Yuhang Zhu arXiv: http://arxiv.org/abs/2605.28054v1 Title: Thom polynomials relative to prescribed maps around the boundary Author: Masato Tanabe arXiv: http://arxiv.org/abs/2603.15010v2 Title: A Casimir obstruction to asymptotically flat black-brane completions of non-supersymmetric 7-branes Author: Yuta Hamada, Hayate Kimura arXiv: http://arxiv.org/abs/2605.25588v1 Title: Beyond Local Detailed Balance: Microscopic Rates Reshape Nonequilibrium Phase Behavior Author: Takahiro Kanazawa, Kyogo Kawaguchi, Kyosuke Adachi arXiv: http://arxiv.org/abs/2605.25406v1 Title: The Pseudospectral Method for the Dirac Equation with Confining Potential Author: Dengshan Liu, Huihui Xie, Pengxiang Du, Jian Li, Tomoya Naito arXiv: http://arxiv.org/abs/2605.25390v1 Title: Thermal Spin Polarization Driven by Nuclear Spin-Orbit Coupling in Neutron Star Pasta Author: Hiroyuki Tajima, Yuta Sekino, Hiroshi Funaki, Shota Kisaka, Nobutoshi Yasutake, Mamoru Matsuo arXiv: http://arxiv.org/abs/2605.25067v1 Title: Dense $\mathrm{QC_2D_2}$ with uniform matrix product states Author: Kohei Fujikura, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2605.17183v1 Title: Detectability of avoided crossings in black hole ringdowns Author: Hayato Imafuku, Naritaka Oshita, Hiroki Takeda arXiv: http://arxiv.org/abs/2605.16199v1 Title: Spin Hall effect and Berry curvature of gravitons from quantum field theory Author: Ritsuki Ito, Kazuya Mameda, Naoki Yamamoto arXiv: http://arxiv.org/abs/2605.19817v1 Title: Multiwavelength Probes of Cosmic Ray Transport in Molecular Cloud Structures Author: Hayden P. H. Ng, Ellis R. Owen, Naomi Tsuji, Szu-Ting Chen arXiv: http://arxiv.org/abs/2605.16698v1 Title: Multicellular simulations with shape and volume constraints using optimal transport Author: Antoine Diez, Jean Feydy arXiv: http://arxiv.org/abs/2402.17086v4 Title: Editorial Trajectories in Wikipedia Reflect Underlying Hyperlink Structure Author: Yeonji Seo, Mi Jin Lee, Seung-Woo Son, Hang-Hyun Jo, Yohsuke Murase arXiv: http://arxiv.org/abs/2605.16850v1
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2026-05-26
Press ReleaseIdentifying 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.
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2026-05-25
Press Release
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.
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2026-05-21
Paper of the WeekWeek 4, May 2026
Title: Black-hole formation and thermalization in open JT gravity Author: Ryo Adachi, Rumi Hasegawa, Takanori Ishii, Daichi Takeda arXiv: http://arxiv.org/abs/2605.14573v1 Title: Simulation of vibrational dynamics using qubits and qudits Author: Erik Lötstedt, Kaoru Yamanouchi arXiv: http://arxiv.org/abs/2605.12866v1
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2026-05-18
Hot Topic
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.
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2026-05-18
Hot Topic
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.
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2026-05-14
Hot Topic
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.
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2026-05-14
Paper of the WeekWeek 3, May 2026
Title: A Monte Carlo Study of the Dipolar Universality Class in Three Dimensions Author: Akira Matsumoto, Yu Nakayama, Toshiki Onagi, Slava Rychkov arXiv: http://arxiv.org/abs/2605.11573v1 Title: A stabilized dual-SAV parametric finite element framework for constrained planar geometric flows with mesh regularization Author: Koya Sakakibara arXiv: http://arxiv.org/abs/2605.11721v1 Title: Non-Parametric Equation of State Reveals Non-Conformal Behavior Beyond Neutron Star Densities Author: Yong-Jia Huang, Shao-Peng Tang, Yi-Zhong Fan arXiv: http://arxiv.org/abs/2605.08584v1 Title: Cooling of Isolated Neutron Stars with Hyperon-mixed Kaon-Condensation Matter Author: Bhavnesh Bhat, Akira Dohi, Takumi Muto, Tsuneo Noda arXiv: http://arxiv.org/abs/2605.09723v1 Title: Classification of Chimera States via Fourier Analysis and Unsupervised Learning Author: Rommel Tchinda Djeudjo, Riccardo Muolo, Thierry Njougouo, Timoteo Carletti arXiv: http://arxiv.org/abs/2605.09401v1 Title: Chemical Bond Analysis in Biomolecular Systems Using Intrinsic Atomic and Bond Orbitals (IAOs and IBOs) with PySCF Author: Mariia Ivonina doi: https://doi.org/10.26434/chemrxiv.15002966/v1 Title: Positivity of the gravitational path integral implies the axionic weak gravity conjecture Author: Gabriele Di Ubaldo, Luca V. Iliesiu, Henry W. Lin, Cynthia Yan arXiv: http://arxiv.org/abs/2605.05305v1
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2026-05-11
Hot Topic
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.
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2026-05-11
Hot Topic
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.
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2026-05-07
Paper of the WeekWeek 2, May 2026
Title: Implementation of the Habegger--Lin decision algorithm Author: Yuka Kotorii, Atsuhiko Mizusawa arXiv: http://arxiv.org/abs/2605.04433v1 Title: Quasinormal modes and continuum response of de Sitter black holes via complex scaling method Author: Shoya Ogawa, Okuto Morikawa, Takuya Hirose arXiv: http://arxiv.org/abs/2605.03277v1 Title: Generalized Free Fields in de Sitter from 1D CFT Author: Kanato Goto, Alexey Milekhin, Herman Verlinde, Jiuci Xu arXiv: http://arxiv.org/abs/2605.03037v1 Title: Loop expansion in polymer field theory: application to phase separation Author: Kiyoharu Kawana, Kyosuke Adachi arXiv: http://arxiv.org/abs/2605.01261v1 Title: A variational approach to estimating the state of a magma reservoir from observed displacement Author: Shungo Kun Tonoyama, Atsushi Suzuki, Takemasa Miyoshi arXiv: http://arxiv.org/abs/2605.00409v1 Title: Examination of the $c\bar{c}+n+^{10}$Be bound-state problem within three cluster models based on QCD charmonium-nucleon interactions Author: Faisal Etminan arXiv: http://arxiv.org/abs/2604.27652v1 Title: Anomalous tunneling as a low-energy theorem for Nambu-Goldstone modes Author: Keisuke Fujii, Daichi Kagamihara, Masaru Hongo arXiv: http://arxiv.org/abs/2604.27489v1
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2026-04-30
Award
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!
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2026-04-30
Hot Topic
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 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. 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 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 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.). 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.
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2026-04-30
Paper of the WeekWeek 5, April 2026
Title: Chimera states on m-directed hypergraphs Author: Rommel Tchinda Djeudjo, Timoteo Carletti, Hiroya Nakao, Riccardo Muolo doi: https://doi.org/10.1103/j1zm-98yt arXiv: http://arxiv.org/abs/2506.12511v5
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2026-04-27
Award
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!
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2026-04-23
Paper of the WeekWeek 4, April 2026
Title: Interaction between nuclear clusters and superfluid phonons in the neutron-star inner crust Author: Masayuki Matsuo, Arata Nishiwaki, Toshiyuki Okihashi, Masaru Hongo arXiv: http://arxiv.org/abs/2604.20725v1 Title: Complex scaling approach to quasinormal modes of Schwarzschild and Reissner--Nordström black holes Author: Shoya Ogawa, Takuya Hirose, Okuto Morikawa arXiv: http://arxiv.org/abs/2604.20442v1 Title: Understanding supernova gravitational waves with protoneutron star asteroseismology Author: Hajime Sotani arXiv: http://arxiv.org/abs/2604.19557v1 Title: Merger rate of initially clustered primordial black holes for the two-body channel Author: Kentaro Kasai, Masahiro Kawasaki, Kai Murai, Shunsuke Neda arXiv: http://arxiv.org/abs/2604.19316v1 Title: A unified framework for efficient quantum simulation of nonlinear spectroscopy Author: Long Xiong, Xiaoyang Wang, Xiaoxia Cai, Xiao Yuan arXiv: http://arxiv.org/abs/2604.16164v1 Title: PSMC-FAC: Automated Optimization of False-Negative Rate Corrections for Low-Coverage PSMC-Based Demographic Inference Author: Francisco Iglesias-Santos, Alba Nieto, Sònia Casillas, Antonio Barbadilla, Carlos Sarabia Journal Reference: Biology 2026, 15(8), 631 doi: https://doi.org/10.3390/biology15080631
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2026-04-23
Hot Topic
The third RIKEN Quantum internal meeting on March 30, 2026
On Monday, March 30, the third RIKEN Quantum internal meeting was held in the Large Conference Room (2F, Administrative Headquarters) at RIKEN, Wako, attended by a total of over 50 RIKEN Quantum members and related researchers. At this meeting, Yahui Chai and Danny Jammooa, who were invited from overseas, gave presentations on their recent research, 'Quantum Simulation of Particle Scattering' and 'Parametric Matrix Models,' respectively. Furthermore, Jian Xu, who recently joined RIKEN Quantum, presented the research he plans to pursue at the institute. In addition, 12 researchers from various fields associated with RIKEN Quantum, who also serve as RIKEN TRIP visiting scientists for collaborative projects, gave short talks to introduce their work. At the banquet following the meeting, members, including those meeting for the first time, exchanged ideas in a relaxed atmosphere, leading to fruitful discussions for the further development of RIKEN Quantum. Reported by Shinichiro Fujii
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2026-04-21
Award
Keiya Hirashima received FY2025 RIKEN Research and Technology Incentive Award (RIKEN OHBU Award 理研桜舞賞)
Keiya Hirashima (Special Postdoctoral Researcher, iTHEMS) has been awarded the FY2025 RIKEN Research and Technology Incentive Award (RIKEN OHBU Award). The RIKEN OHBU Award is presented to early-career researchers and staff members at RIKEN who have demonstrated outstanding achievements in research and development, research support, or contributions to the promotion and dissemination of research outcomes, through active research activities. Hirashima was recognized for his work entitled “Establishment of galaxy simulations resolving individual stars through the integration of AI surrogate models and large-scale parallel computing.” This work integrates advanced AI surrogate modeling with large-scale parallel computation to enable high-resolution galaxy simulations that resolve individual stars, contributing to a deeper understanding of galaxy formation and evolution. Congratulations, Keiya!
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2026-04-21
Award
Masazumi Honda received FY2025 RIKEN Excellent Achievement Award (RIKEN BAIHO Award 理研梅峰賞)
Masazumi Honda (Senior Research Scientist, iTHEMS) has been awarded the FY2025 RIKEN Excellent Achievement Award (RIKEN BAIHO Award). The RIKEN BAIHO Award is presented by the President of RIKEN to individuals who have achieved original and outstanding research and development results that are expected to receive high recognition in academic communities, or who have made distinguished contributions to research support both within and outside the institute. Honda was recognized for his work entitled “Development of non-perturbative methods in quantum field theory and quantum gravity.” This work develops novel theoretical approaches to analyze strongly coupled phenomena in quantum field theory and quantum gravity, and is expected to contribute to the advancement of fundamental physics through a deeper understanding of non-perturbative dynamics. Congratulations, Masazumi!
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2026-04-21
Award
Leo Speidel, RIKEN ECL Research Unit Leader, Receives the SMBE Early-Career Excellence Award
Leo Speidel, RIKEN ECL Research Unit Leader of the Mathematical Genomics RIKEN ECL Research Unit, Division of Fundamental Mathematical Science, RIKEN iTHEMS, has been awarded the 2026 SMBE Early-Career Excellence Award on March 12, 2026. This award is presented by the Society for Molecular Biology and Evolution (SMBE) to researchers who have made significant contributions to the advancement of the field through innovative research and who embody the values of the society through activities such as education and outreach. He has advanced research on genetic data analysis using mathematical approaches, providing new insights into molecular evolution and population genetics. This award recognizes his research achievements and contributions to the field. Congratulations, Leo!
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2026-04-16
Paper of the WeekWeek 3, April 2026
Title: Generalised (bi-)Hamiltonian structures of hydrodynamic type and (bi-)flat F-manifolds Author: Paolo Lorenzoni, Zhe Wang arXiv: http://arxiv.org/abs/2604.12819v1 Title: Interaction-powered Type Ibn Supernovae as a Transient PeVatron Candidate: The Case of SN 2023uqf Author: Ryo Sawada, Yusuke Inoue, Yosuke Ashida arXiv: http://arxiv.org/abs/2604.12496v1 Title: Exact SL(2,Z)-Structure of Lattice Maxwell Theory with $θ$-term in Modified Villain Formulation Author: Shoto Aoki, Yoshio Kikukawa, Toshinari Takemoto arXiv: http://arxiv.org/abs/2604.08736v1
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2026-04-10
Hot Topic
Talk Event “Useless Science & Art” Held at the Museum of Contemporary Art Tokyo
As a related program of the Mission∞Infinity exhibition at the Museum of Contemporary Art Tokyo, the talk event “Useless Science & Art: The Usefulness of ‘Useless’ Science and Art” was held on Saturday, March 21, 2026, attracting 119 participants. This event was organized as a continuation of “Entangle Moment [Quantum, Sea, and Universe] × Art,” held at the EXPO Messe “WASSE” during Expo 2025 Osaka, Kansai, from August 14 to 20, 2025, which welcomed approximately 60,000 visitors in total. Continuing the momentum of that initiative, the event brought together iTHEMS researchers and artists to discuss the value of scientific research and artistic expression that may initially appear “useless.” Using Black Hole Recorder, a work inspired by quantum black hole theory, as a starting point, participants shared multifaceted perspectives on the relationship between science and creativity. Audience members also actively engaged in the discussion, raising numerous questions and exchanging ideas about the relationship between science and art and how their value should be understood. The venue was filled with lively and enthusiastic discussion throughout the event. Expanding further on the fusion of science and art sparked by the Expo, the event provided a valuable opportunity to reflect on the nature of knowledge from a long-term perspective. The Mission∞Infinity: Space, Quantum, and Art exhibition at the Museum of Contemporary Art Tokyo, including the display of Useless Prototyping Studio’s Black Hole Recorder, will continue through Wednesday, May 6, 2026 (national holiday).
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2026-04-09
Award
Ryo Sawada Receives the Young Investigator Award from the Japan Forum of Nuclear Astrophysics (UKAKUREN)
Ryo Sawada, a Special Postdoctoral Researcher at RIKEN iTHEMS, received the 2nd Young Investigator Award from the Japan Forum of Nuclear Astrophysics (UKAKUREN) on March 31, 2026. The research recognized with this award concerns the impact of cosmic-ray environments originating from past supernovae on the formation of Earth-like planets [1]. Congratulations Ryo!
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2026-04-09
Award
Akira Dohi Receives the Young Investigator Award from the Japan Forum of Nuclear Astrophysics (UKAKUREN)
Akira Dohi, a Special Postdoctoral Researcher at the RIKEN Pioneering Research Institute (PRI) and concurrently affiliated with RIKEN iTHEMS, received the 2nd Young Investigator Award from the Japan Forum of Nuclear Astrophysics (UKAKUREN) on March 31, 2026. The paper [1], recognized with this award, presents a theoretical study of clocked X-ray bursters. This work also represents the scientific result from NinjaSat, the world’s first ultra-small general-purpose X-ray satellite, launched on November 11, 2023 under the leadership of the Tamagawa High-Energy Astrophysics Laboratory at RIKEN PRI. For further details, please refer to the press release issued by RIKEN PRI via the related link. Congratulations Akira!
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2026-04-09
Paper of the WeekWeek 2, April 2026
Title: Twisted doughnuts: Thick disk torus around equatorial asymmetric black hole Author: Che-Yu Chen, Eva Hackmann, Audrey Trova arXiv: http://arxiv.org/abs/2604.05604v1 Title: Gauss law codes and vacuum codes from lattice gauge theories Author: Javier P. Lacambra, Aidan Chatwin-Davies, Masazumi Honda, Philipp A. Hoehn arXiv: http://arxiv.org/abs/2604.06087v1 Title: Reconstruction of fast-rotating neutron star observables with the neural network Author: Wen Liu, Lingxiao Wang, Zhenyu Zhu arXiv: http://arxiv.org/abs/2604.05428v1 Title: Electroweak Doublet Dark Matter for a Galactic Halo Gamma-Ray Excess Author: Yasunori Nomura, Tomonori Totani arXiv: http://arxiv.org/abs/2604.05016v1 Title: Cosmological collider signals of modular spontaneous CP breaking Author: Shuntaro Aoki, Alessandro Strumia arXiv: http://arxiv.org/abs/2604.05548v1 Title: Mechanochemical instabilities drive digit morphogenesis in organoids Author: Rio Tsutsumi, Antoine Diez, Steffen Plunder, Ryuichi Kimura, Shinya Oki, Kaori Takizawa, Rei Nakano, Haruhiko Akiyama, Ritsuko Takada, Shinji Takada, Marco Musy, James Sharpe, Mototsugu Eiraku doi: https://doi.org/10.1101/2025.08.31.673315 Title: Multi-field oscillons/I-balls in the Friedberg-Lee-Sirlin model Author: Kai Murai, Tatsuya Ogawa, Fuminobu Takahashi arXiv: http://arxiv.org/abs/2604.04494v1 Title: Exponentially Long Evaporation of Noncommutative Black Hole Author: Pei-Ming Ho, Wei-Hsiang Shao, Takuya Yoda arXiv: http://arxiv.org/abs/2604.04774v1 Title: Type-IV 't Hooft Anomalies on the Lattice: Emergent Higher-Categorical Symmetries and Applications to LSM Systems Author: Tsubasa Oishi, Hiromi Ebisu arXiv: http://arxiv.org/abs/2604.02856v1 Title: Continuous-time evolution via probabilistic angle interpolation and its applications Author: Tomoya Hayata, Yuta Kikuchi arXiv: http://arxiv.org/abs/2604.02854v1 Title: Phase transitions in parametrized quantum circuits Author: Xiaoyang Wang, Han Xu, Lukas Broers, Tomonori Shirakawa, Seiji Yunoki arXiv: http://arxiv.org/abs/2603.27532v1 Title: Angular momentum transport in the convection zone of a 3D MHD simulation of a rapidly rotating core-collapse progenitor Author: Ryota Shimada, Lucy O. McNeill, Vishnu Varma, Keiichi Maeda, Takaaki Yokoyama, Bernhard Müller arXiv: http://arxiv.org/abs/2603.26550v1 Title: Cosmology from asymptotically safe Proca theories Author: Carlos Pastor-Marcos, Lavinia Heisenberg, Álvaro Pastor-Gutiérrez, Jan M. Pawlowski, Manuel Reichert arXiv: http://arxiv.org/abs/2604.01090v1 Title: Lindbladian Simulation with Commutator Bounds Author: Xinzhao Wang, Shuo Zhou, Xiaoyang Wang, Yi-Cong Zheng, Shengyu Zhang, Tongyang Li arXiv: http://arxiv.org/abs/2603.28602v1 Title: Disentangling the interactive effects of anthropogenic disturbances on biodiversity Author: Isaac Planas-Sitjà, Ryosuke Iritani, Adam L. Cronin arXiv: http://arxiv.org/abs/2603.29116v1 Title: Gravitational waves from gaps of neutron stars Author: Akira Dohi, Asuka Ito, Shota Kisaka arXiv: http://arxiv.org/abs/2603.29514v1 Title: Universal Non-Gaussian Signatures from Transient Instabilities Author: Shuntaro Aoki, Diederik Roest, Denis Werth arXiv: http://arxiv.org/abs/2604.01035v1 Title: Evaluating Phylogenetic Comparative Methods under Reticulate Evolutionary Scenarios Author: Lydia Morley, Emma Lehmberg, Sungsik Kong arXiv: http://arxiv.org/abs/2603.25986v1 Title: Segmentation of monotone data by Kobayashi-Warren-Carter type total variation energies Author: Yoshikazu Giga, Ayato Kubo, Hirotoshi Kuroda, Koya Sakakibara arXiv: http://arxiv.org/abs/2603.28078v2 Title: Zeta Zeros in a Narrow Vertical Box Author: Daniel A. Goldston, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2603.28104v1 Title: Finite-nuclear-size effect for hydrogenlike ions under high external pressure Author: Dengshan Liu, Huihui Xie, Pengxiang Du, Tianshuai Shang, Jian Li, Jiguang Li, Tomoya Naito arXiv: http://arxiv.org/abs/2603.22901v1
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2026-04-06
Person of the Week
Self-introduction: Yuta Hamada
I am interested in particle physics such as string theory and early universe cosmology. Recently, I am working on identifying consistent gravitational effective field theories that can be ultraviolet completed. Additionally, I am interested in applying AI and quantum computing to string theory and quantum field theory.
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2026-04-02
Hot Topic
KEK-iTHEMS Workshop “Concepts of Quantum and Spacetime” on March 9, 2026
We held the workshop “Concepts of Quantum and Spacetime” (at KEK in Japan from 9 to 12 March 2026), a joint workshop organized by KEK Theory Center and RIKEN iTHEMS. The two fundamental questions, “What is quantum?” and “What is spacetime?”, are deeply intertwined. The workshop discussed the question “How can quantum theory and spacetime be understood in a consistent manner?” from a fundamental and broad perspective and shared various ideas with open minds, to find directions guiding quantum theory over the next 100 years. The topics were diverse: foundations of quantum theory, quantum gravity, emergence of spacetime, formulation of semi-classical gravity, experimental aspects of fundamental properties in nature, and foundations of quantum many-body systems and thermodynamics. Around 90 researchers from various countries, generations, and fields came together. (Around 40% of these were from overseas.) The 14 keynote speakers—many of whom are rarely seen in Japan—shared their visions on quantum theory and spacetime. (The talk slides are available in the website.) The 13 selected short talks and the 22 poster presentations were of a high standard, leading to lively discussions; we also held a poster award competition. Interestingly, the disagreements and confusion arising from differences in their expertise and viewpoints actually gave rise to new discussions and ideas. This was likely due to the open atmosphere of sincere engagement that emerged because the thema was not confined to specific methods or theoretical frameworks. Furthermore, small yet significant touches—such as providing boxed lunches to keep the lively atmosphere of the lecture hall going during the lunch break, and setting up whiteboards in open spaces to encourage discussion—proved effective. These efforts fostered constant, natural interaction and lively discussion throughout the venue. Participants did not merely listen; they truly shaped the workshop. (Visit the website to see photos during the event.) Many participants commented that it was an interesting and wonderful workshop. We also received feedback such as, “I gained ideas for future research,” and “This provided valuable insights for organizing future workshops.” These are the result of the deep curiosity shared by all participants regarding fundamental questions, “What is quantum?” and “What is spacetime?” It is precisely such curiosity that will naturally give rise to new ideas and collaborative research and connect the world. I hope that workshops embodying a similar spirit will be held around the world on a variety of themes in the future. Reported by Yuki Yokokura, chair of organizing committee.
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2026-04-02
Paper of the WeekWeek 1, April 2026
Title: Nonlocal operators on the lattice for the Higgs-confinement phase transition Author: Yusuke Shimada, Arata Yamamoto Journal Reference: J.Subatomic Part.Cosmol. 5, 100267 (2026) doi: https://doi.org/10.1016/j.jspc.2025.100267 Title: The 'Forgotten' Neutrons: Implications for the Propagation of High-Energy Cosmic Rays in Magnetized Astrophysical and Cosmological Structures Author: Ellis R. Owen, Kinwah Wu, Yoshiyuki Inoue, Tatsuki Fujiwara, Qin Han, Hayden P. H. Ng arXiv: http://arxiv.org/abs/2603.25060v1 Title: Josephson effects in an interaction-asymmetric junction across the BCS-BEC crossover Author: Tingyu Zhang, Hiroyuki Tajima arXiv: http://arxiv.org/abs/2603.25577v1
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2026-04-02
Person of the Week
Self-introduction: Muzi Hong
I am doing research in cosmology, especially in early universe physics. Recently, I have been working on topics such as inflation, cosmological perturbations, baryogenesis, and dark energy. Cosmology is an interdisciplinary field, and I look forward to discussing various topics in physics with researchers from other fields.
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2026-04-02
Press Release
Observation of Regular Oscillations in Magnetization with a Quantum Computer
A research group including Senior Research Scientist Tomonori Shirakawa demonstrated that discrete time crystals and discrete time quasicrystals can be stably realized for up to 100 time steps on a 133-qubit two-dimensional lattice using IBM’s superconducting quantum computer (here, one time step corresponds to one period of the drive). This result is expected to contribute to experimental validation toward digital quantum simulation of two-dimensional nonequilibrium quantum many-body systems, which are difficult to simulate using classical computation. For further details, please refer to the related link.
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2026-04-01
Award
Yuta Sekino received FY2025 RIKEN Research and Technology Incentive Award (RIKEN OHBU Award 理研桜舞賞)
Yuta Sekino (Postdoctoral Researcher, iTHEMS) has been awarded the FY2025 RIKEN Research and Technology Incentive Award (RIKEN OHBU Award). The RIKEN Ohbu Award is presented to early-career researchers and staff members at RIKEN who have demonstrated outstanding achievements in research and development, research support, or contributions to the promotion and dissemination of research outcomes, through active research activities. Sekino was recognized for his proposal entitled “Quantum simulation of spin transport using ultracold atomic gases.” This work presents a novel theoretical framework for simulating and understanding spin transport phenomena in quantum many-body systems using ultracold atom platforms, and is expected to contribute to the advancement of quantum simulation and quantum condensed matter physics. Congratulations, Yuta!
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2026-03-31
Hot Topic
Farewell message from Takashi Satomi
Our colleague, Takashi Satomi, will be joining Tokyo Denki University as a Lecturer starting April 2026. We will all miss him and wish him the best of luck in this new endeavor. Here is a message from Takashi: I would like to share that I will be leaving my position as an SPDR at iTHEMS. Although my term was originally planned to continue, I have decided to end it early as I will start a new position as a lecturer at Tokyo Denki University from April. I have been a member of iTHEMS as an SPDR from April 2024 to March 2026. During this time, I greatly enjoyed the open and interdisciplinary environment. Discussions with researchers from different fields gave me many new ideas and perspectives, and these experiences have been very valuable for my research. I would like to express my sincere thanks to all the members at iTHEMS for their support and kindness. From April, I will continue to be affiliated with iTHEMS as a visiting researcher. I hope to continue discussions and collaborations in the future. Thank you very much for everything.
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