Monitoring the complexity and dynamics of mitochondrial translation

February 12 (Thu) 16:00 - 17:00, 2026

Taisei Wakigawa (Research Associate, RNA Systems Biochemistry Laboratory, RIKEN Pioneering Research Institute (PRI))

Since mitochondrial translation leads to the synthesis of the essential oxidative phosphorylation (OXPHOS) subunits, exhaustive and quantitative delineation of mitoribosome traversal is needed. Here, we developed a variety of high-resolution mitochondrial ribosome profiling derivatives and revealed the intricate regulation of mammalian mitochondrial translation. Harnessing a translation inhibitor, retapamulin, our approach assessed the stoichiometry and kinetics of mitochondrial translation flux, such as the number of mitoribosomes on a transcript, the elongation rate, and the initiation rate. We also surveyed the impacts of modifications at the anticodon stem loop in mitochondrial tRNAs (mt-tRNAs), including all possible modifications at the 34th position, in cells deleting the corresponding enzymes and derived from patients, as well as in mouse tissues. Moreover, a retapamulin-assisted derivative and mito-disome profiling revealed mitochondrial translation initiation factor (mtIF) 3-mediated translation initiation from internal open reading frames (ORFs) and programmed mitoribosome collision sites across the mitochondrial transcriptome. Our work provides a useful platform for investigating protein synthesis within the energy powerhouse of the cell.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Recent progress in the resource theory of asymmetry and its applications

February 12 (Thu) 13:30 - 15:00, 2026

Hiroyasu Tajima (Associate Professor, Department of Informatics, Faculty of Information Science and Electrical Engineering, Kyushu University)

If you are not affiliated with RIKEN, please register using the registration form. Registration deadline: 12nd Feb. (Thu), 2026 Symmetry and symmetry breaking are among the central themes in physics and have attracted the interest of many physicists. Recently, the resource theory of asymmetry (RTA) [1-4], which approaches these issues from the perspective of resource theories, has been actively studied. In the past few years, several foundational advances have been made in this framework. In particular, the iid-complete monotone that plays a role analogous to entanglement entropy has been identified for arbitrary compact Lie groups [2] as well as for arbitrary finite groups [3]. The resolution for compact Lie groups includes, as a corollary, a solution to the Marvian–Spekkens conjecture [4]. Building on this theoretical foundation, several developments related to the Wigner–Araki–Yanase (WAY) theorem [5-7] have also been obtained. These include extensions of the WAY theorem to the implementation of arbitrary unitary gates [8], and a unification of the WAY-type theorems, i.e. the WAY theorem, the Eastin–Knill theorem (a fundamental limitation on error correction under symmetry) [9], and the above unitary-gate results. The unification is formulated a universal trade-off inequality relating symmetry, irreversibility, and quantumness for arbitrary quantum dynamics [10]. Using this tradeoff relation, the WAY-type limitations can now be applied, for example, to quantum thermodynamics[11] and black hole evaporation [10] etc. If time permits, I will also briefly touch upon some other recent developments, such as extensions of the above tradeoff and the WAY theorem to general resource theory beyond symmetry [12].

Venue: #359, Seminar Room #359

Event Official Language: English

Quantum Electrodynamics of Strong Laser-Matter Interaction: The Ongoing Journey and Beyond

February 10 (Tue) 10:00 - 12:00, 2026

Ciappina Marcelo (Professor, Guangdong Technion, China)

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Finite-size effects on the QCD critical point

February 9 (Mon) 15:30 - 17:30, 2026

Gyozo Kovacs (Research Fellow, Institute of Theoretical Physics, University of Wroclaw, Poland)

[Joint seminar hosted by QMS Team (iTHEMS) and FTR Team (R-CCS)] While effective approaches are important tools in the search for the QCD critical point, the physical systems they describe differ in several aspects from those in heavy-ion collisions and from unextrapolated lattice QCD. A primary discrepancy is the system size, which is infinite only in effective model calculations. Various implementations exist to account for the resulting finite-size effects. Beyond the frequently used methods, we present a comprehensive mean-field approach that allows for both infinite- and finite-size calculations, even within a complex parameter space. We discuss the general impact of finite-size effects on key observables, such as conserved charge fluctuations, and on the analytic structure of the thermodynamic potential. 15:30-16:30 Lecture 16:30-17:30 Discussion with coffee

Venue: #359, Main Research Building (Main Venue) / via Zoom

Event Official Language: English

What can we learn from kilonovae about nucleosynthesis and high-density matter?

February 9 (Mon) 14:00 - 15:15, 2026

Oliver Just (Postdoctoral Researcher, GSI Helmholtzzentrum für Schwerionenforschung, Germany)

The electromagnetic transients accompanying neutron-star mergers (NSMs), called kilonovae, are powered by the radioactive decay of freshly synthesized heavy elements. As such they should contain rich information about the ejected matter and the properties of the extremely dense meta-stable neutron-star remnant formed right after the collision. However, extracting such information from observed kilonova light curves and spectra remains a challenging endeavor, which requires sophisticated models of various hydrodynamic processes and neutrino transport effects, detailed knowledge of nuclear and atomic physics, as well as complex radiative transfer calculations. In this talk I will report recent efforts from our "HeavyMetal" collaboration aimed at deciphering kilonovae.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Mathematical Application Research Team Meeting #12

February 6 (Fri) 14:00 - 15:30, 2026

Riccardo Muolo (Special Postdoctoral Researcher, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

Mathematical Application Research Team invites Riccardo Muolo fom Division of Fundamental Mathematical Science to this meeting. You are welcome to join the meeting. Title: Dynamics beyond nodes: a topological framework for oscillatory dynamics on higher-order networks Abstract: In recent years, increasing attention has been given to dynamical processes taking place on higher-order networks, where interactions are not limited to links, but may involve also higher-dimensional simplices [1]. While classical network models assume that state variables live on nodes and interact through links, many real systems — including brain, climate, and transportation systems — cannot be fully described within this node-centric perspective [2]. In this seminar, I will introduce the framework of higher-order networks and the concept of topological signals, namely, dynamical variables defined on simplices of higher dimensions. I will briefly present the basic tools required for this setting, including elementary notions of discrete calculus, discrete topology and geometric algebra, which serve as the mathematical foundation for modeling dynamical processes beyond the node-based paradigm. Next, I will discuss models of oscillatory dynamics extended to this framework. First, I will present the topological Kuramoto model [3], in which phases are not restricted to nodes but may also be associated with links, and where the coupling arises from the combinatorial structure of the simplicial complex. Then, I will introduce the discrete Hodge Laplacian and the Dirac-Bianconi operator [4], the former generalizing diffusive interactions to the higher-order setting, while the latter provides cross-talk between signals defined on simplices of different dimensions. Finally, I will introduce the notion of Dirac-Bianconi driven oscillators, where the dynamics of node- and link-signals coexist, interact and may give rise to collective oscillatory behaviors [5].

Venue: #359, 3F, Main Research Building (Main Venue) / via Zoom

Event Official Language: English

Quantitative characterization of microbial diversity and environmental adaptation

February 5 (Thu) 13:00 - 14:30, 2026

Mio Matsumoto (Junior Research Associate, Geobiology and Astrobiology Laboratory, RIKEN Pioneering Research Institute (PRI))
Shino Suzuki (Chief Scientist, Geobiology and Astrobiology Laboratory, RIKEN Pioneering Research Institute (PRI))

Event Official Language: English

Scalable Simulation of Quantum Many-Body Dynamics with Or-Represented Quantum Algebra

February 4 (Wed) 14:30 - 16:00, 2026

Lukas Broers (Postdoctoral Researcher, Computational Materials Science Research Team, RIKEN Center for Computational Science (R-CCS))

High-performance numerical methods are essential for advancing quantum many-body physics, as well as for enabling the integration of supercomputers with emerging quantum computing platforms. We have developed a scalable and general-purpose numerical framework for quantum simulations based on or-represented quantum algebra (ORQA). This framework applies to arbitrary spin-systems and naturally integrates with quantum circuit simulation in the Heisenberg picture, particularly relevant to recent large-scale experiments on superconducting qubit processors [Kim et al., Nature 618, 500 (2023)]. As a benchmark, we simulate the kicked Ising model on a 127-qubit heavy-hexagon lattice, successfully tracking the time-evolution of local magnetization using up to one trillion Pauli strings. Our simulations exhibit strong scaling up to 2^17 parallel processes with near-linear communication overhead. Further, we show that our framework is naturally extended to a broader range of quantum systems, superseding the capabilities of recently established Pauli propagation methods. We present possible future directions on how to utilize our algorithm.

Venue: via Zoom / Seminar Room #359

Event Official Language: English

JST-Sakura Science Exchange Program: AI for Atmospheric Science

February 4 (Wed) - 10 (Tue) 2026

This JST-Sakura Science Exchange Program leverages the complementary strengths and research foundations of Fudan University and RIKEN in atmospheric science, focusing on the important scientific challenge of applying artificial intelligence to cloud remote sensing and data assimilation. The exchange program also includes one-day workshop in R-CCS with Data Assimilation Research Team.

Venue: S704-S705, Integrated Innovation Building (IIB) (Main Venue) / via Zoom / RIKEN Center for Computational Science, 1F Seminar room

Event Official Language: English

From Wavefunction Sparsity to Quantum Filter-Assisted Subspace Diagonalization

February 4 (Wed) 13:00 - 14:30, 2026

Han Xu (Postdoctoral Researcher, Computational Materials Science Research Team, RIKEN Center for Computational Science (R-CCS))

Subspace diagonalization techniques based on quantum sampling, such as quantum selected configuration interaction (QSCI) and sample-based quantum diagonalization (SQD), are a class of quantum-centric algorithms for approximating ground-state energies of many-body systems. One of the foundational bottlenecks for SQD is due to the lack of compactness of the ground-state wavefunctions. In this talk, we will introduce a filter-assisted SQD protocol that enhances the wavefunction sparsity through a quantum-circuit transformation of the Hamiltonian. Using the Gini coefficient as a robust sparsity measure, we clarify how sparsity determines the resource requirements of SQD. To construct the quantum filter, we develop a tensor-network-based automatic circuit-encoding algorithm that encodes the target matrix product states with controllable fidelity. We benchmark the method on the quantum Ising model under the transverse and longitudinal fields, using both numerical simulations and experiments on IBM quantum hardware. Our results show that the filter-assisted protocol reduces energy-estimation errors by orders of magnitude and substantially lowers the overhead of measurement compared with standard SQD, which highlight the potential of filter-assisted protocol in quantum-centric computing for strongly correlated materials.

Venue: via Zoom / Seminar Room #359

Event Official Language: English

International Workshop on Quantum Geometry

February 3 (Tue) - 6 (Fri) 2026

In recent years, quantum geometry has attracted a renewed interest as an important concept in physics, and is being actively studied in a wide variety of fields ranging from condensed matter physics to high-energy physics. This international workshop aims to invite researchers actively working at the forefront of quantum geometry research and hold intensive discussions, thereby providing an opportunity to facilitate mutual interaction that will lead to future collaborations. The workshop will cover a wide range of topics related to quantum geometry, as in condensed matter physics, AMO physics, quantum gravity, quantum information, etc.

Venue: 1F, Lecture Room #112, Information Science Bldg. (C43) (Main Venue) / Satellite : 4F, "Common Space" of FQSP, Information Science Bldg.(C43)

Event Official Language: English

Gauge fixing for open systems: A pathway to open gravity EFTs

January 30 (Fri) 14:00 - 16:00, 2026

Maria Mylova (Project Researcher, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU))

Understanding how to gauge-fix open quantum field theories is essential for building consistent open frameworks for cosmology and gravity, where gauge symmetry must coexist with dissipation and noise and decoherence. I will present our recent work developing explicit top-down constructions of open effective field theories (EFTs) for gauge degrees of freedom, with particular emphasis on the role of gauge fixing. We implement BRST quantisation on the Schwinger-Keldysh contour and show that the in-in boundary conditions reduce the doubled global BRST symmetry to a single diagonal copy. This diagonal BRST symmetry is nevertheless sufficient to guarantee that the influence functional remains gauge invariant under two independent gauge transformations, retarded and advanced, independently of the choice of initial state, the presence of symmetry-breaking phases, and whether the gauge theory is Abelian or non-Abelian. We further clarify how this is compatible with the decoupling limit, in which the global advanced symmetry is generically broken by the state. I will conclude by outlining bottom-up implications, and how these principles provide a systematic route to causal, gauge-invariant open EFTs suitable for cosmological and gravitational applications.

Venue: #445-447, 4F (Hybrid), Main Research Building

Event Official Language: English

Development of a real-time object tracking and response system

January 29 (Thu) 13:00 - 14:00, 2026

Isaac Planas Sitja (Postdoctoral Researcher, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

I will introduce the real-time tracking software and automatic response system that we are developing: TracktorLive. We created a modular system to overcome several issues in close-loop experiments, with the aim to automatise mechanical stimulus delivery or time-consuming actions, and provide tools for VR experiments in animals. This tracker, coded as a Python package, separates the processes into server and client functions to run several processes in parallel, which minimises the frame processing time, and allows running on low-end computers. We hope to implement LLM or AI functions as server processes in the future.

Venue: Seminar Room #359

Event Official Language: English

iTHEMS Cosmology Forum n°5 - Effective Field Theory approaches across the Universe

January 29 (Thu) 10:00 - 17:00, 2026

Katsuki Aoki (Research Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)
Toshifumi Noumi (Associate Professor, Graduate School of Arts and Sciences, The University of Tokyo)
Lucas Pinol (CNRS Researcher, Laboratoire de Physique de l’École Normale Supérieure (LPENS), CNRS/École Normale Supérieure, France)

This fifth workshop will bring together researchers exploring the effective field theory (EFT) framework in diverse cosmological contexts. Topics will include EFT formulations of interacting dark matter and dark energy, open EFTs for gravity, and multi-field inflationary dynamics. By highlighting recent progress and open questions, the workshop seeks to bridge insights from the early and late universe through the unifying language of EFT. In addition to the invited talks, the workshop will feature a panel discussion designed to promote interaction between the speakers and participants. One of the key goals of this event is to foster collaboration among researchers working in neighboring fields, and to encourage participation from young and early-career researchers who are interested in, but may not yet have worked on, these themes. The workshop welcomes a broad audience with an interest in theoretical cosmology, gravitation, and quantum field theory. The workshops are organised by the Cosmology Study Group at RIKEN iTHEMS.

Venue: Okochi Hall

Event Official Language: English

DEEP-IN-iPI Joint Meeting

January 26 (Mon) - 30 (Fri) 2026

Xingyu Guo (Lecturer, Institute of Quantum Matter, South China Normal University, China)
Gert Aarts (Professor, Department of Physics, Swansea University, UK)
Shuzhe Shi (Assistant Professor, Physics Department, Tsinghua University, Beijing, China)
Sung Hak Lim (Senior Researcher, Center for Theoretical Physics of the Universe (CTPU-PTC), Institute for Basic Science (IBS), Republic of Korea)
Jinyang Li (Ph.D. Student, Program of Particle and Nuclear Physics, The Graduate University for Advanced Studies (SOKENDAI))
Yingying Xu (Research fellow, Department of Mathematics and Statistics, University of Helsinki, Finland)

The series of DEEP-IN meetings (Jan 26–30, 2026) are joint with UTokyo Institute for Physics of Intelligence (iπ), which is a multi-day scientific program bringing together researchers to explore quantum simulations, machine learning physics, and applications in particle and nuclear physics. The tentative schedule is, UTokyo-iπ Session (Venue: #512, Faculty of Science Bldg.1, School of Science, UTokyo) Day 1: Jan 26 (Mon) 14:30–16:00 Onset of Bjorken flow in a quantum many-body simulation of the massive Schwinger model, Shuzhe Shi Day 2: Jan 27 (Tue) 14:30–16:00 Physics of Diffusion Models, Gert Aarts 16:00–17:30 Discovering Symmetry from Energy-Based Diffusion Models, Jinyang Li RIKEN-iTHEMS Session (Venue: Seminar Room #359, Main Research Building) Day 3: Jan 28 (Wed) 14:30–16:00 Understanding Galactic Dark Matter with Generative Models, Sung Hak Lim 16:00–18:00 Free Discussion ML Physics-1 Day 4: Jan 29 (Thu) 10:00–11:30 Quantum Simulations of HEP and Beyond, Xingyu Guo 14:30–16:00 Physics of Machine Learning, Gert Aarts 16:00–17:30 Storage capacity of perceptron with variable selection, Yingying Xu Day 5: Jan 30 (Fri) 11:00–14:00: Free Discussion ML Physics-2

Venue: via Zoom / Seminar Room #359 / Faculty of Science Bldg.1, School of Science, The University of Tokyo, Hongo Campus

Event Official Language: English

New computational methods in quantum field theory 2026

January 26 (Mon) - 28 (Wed) 2026

Recent developments in quantum computers and related theoretical/technical advancements have brought attention to "new computational methods in quantum field theory" in the fields of high energy/nuclear physics. Main targets of this school are graduate students and postdocs. This school provides opportunities to discuss recent research trends and their applications through lectures by experts and presentations by participants. Lecturers: Junichi Haruna (University of Osaka) "Introduction to Quantum Error Correction (tentative)" Yoshimasa Hidaka (Yukawa Institute for Theoretical Physics/RIKEN iTHEMS) “Introduction to Hamiltonian Lattice Gauge Theory (tentative)” Tokiro Numasawa (University of Tokyo) "Open Majorana system (tentative)"

Venue: #435-437, 4F, Main Research Building

Event Official Language: English

Evolution of sterile soldier castes in aphids

January 21 (Wed) 13:00 - 14:00, 2026

Keigo Uematsu (Assistant Professor, Keio University)

This seminar is jointly organized with the RIKEN Center for Sustainable Resource Science (CSRS). Social evolution in aphids is tightly linked to the formation of galls on their host plants. Galls provide efficient colony defense and nutritionally rich feeding sites such that colony members need not forage outside, leading to high intra-group relatedness. Typically, social aphids form a gall on their primary host plant, after which winged morphs disperse to secondary host plants and establish a free-living, open colony. Remarkably, sterile soldier castes have independently evolved twice in these open colonies, where individuals live on plant surfaces without modifying their structure. These aphids raise intriguing questions about the prerequisites for eusocial evolution and the mechanisms by which two distinct social systems are maintained within a single genome. In this talk, I will first provide an overview of the life cycle and the diversity of altruistic behaviors in gall-forming aphids, and then present our studies of the evolution of a sterile soldier caste in aphids inhabiting open colonies. From a developmental perspective, we tested the hypothesis that the sterile soldiers evolved through the co-option of pre-existing soldier phenotypes in a gall, based on similarity in morphology, transcriptome and behavior. From an ecological perspective, we investigated the kin structure and altruistic behavior of young nymphs in the open colonies of pre-eusocial species, and demonstrate that young aphids exhibit altruism by yielding feeding sites to older kin. Together, we propose that the open colonies of social aphids provide an ideal model system for studying the evolution of altruism.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Analog variational quantum eigensolver for neutral atomic quantum simulators

January 20 (Tue) 10:00 - 12:00, 2026

Kazuma Nagao (Postdoctoral Researcher, Computational Materials Science Research Team, RIKEN Center for Computational Science (R-CCS))

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Introduction to the gravitational wave background from the primordial universe

January 16 (Fri) 16:00 - 17:15, 2026

Ryo Namba (Senior Research Scientist, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))

Being genuine propagating degrees of freedom of the spacetime metric, gravitational waves (GWs) serve as an independent "eye" through which we can probe the evolution history of our universe. They are complementary to electromagnetic observables such as cosmic microwave background (CMB) and can act as direct messengers from the earliest stage of the universe, where conventional probes lose access. In particular, a stochastic background of GWs is widely regarded as a smoking gun of cosmic inflation. In this talk, I introduce the basic theoretical framework for GWs produced in the primordial universe and discuss how they arise from vacuum fluctuations of the metric. I also outline additional production mechanisms sourced by matter fields in the early universe and contrast their characteristic observational signatures with those of vacuum tensor modes. The emphasis of my talk will be on physical intuition and analytic derivations, with the aim of making the subject accessible to non-specialists in the astrophysics community.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

A one-world interpretation of quantum mechanics

January 16 (Fri) 14:00 - 16:00, 2026

Isaac Layton (Postdoctoral Researcher, Department of Physics, Graduate School of Science, The University of Tokyo)

The measurement problem arises in trying to explain how the objective classical world emerges from a quantum one. In this talk I’ll advocate for an alternative approach, in which the existence of a classical system is assumed a priori. By asking that the standard rules of probability theory apply to it when it interacts with a system linearly evolving in Hilbert space, I’ll show that with a few additional assumptions one can recover the unitary dynamics, collapse and Born rule postulates from quantum theory. This gives an interpretation of quantum mechanics in which classically definite outcomes are always assigned probabilities, rather than superpositions, giving one-world instead of many. The main technical tool used is a change of measure on the space of classical paths, the functional form of which characterises the quantum dynamics and Born rules of a class of quantum-like theories. Time allowing, I will also discuss how these results clarify which additional assumptions must be accepted if one wishes to seriously consider classical alternatives to quantum gravity.

Venue: #445-447, 4F, Main Research Building / via Zoom

Event Official Language: English