Supported by iTHEMS

8th QGG Intensive Lecture: Quantum reference frames and their applications in high-energy physics

September 24 (Wed) - 26 (Fri) 2025

Philipp Höhn (Assistant Professor, Qubits and Spacetime Unit, Okinawa Institute of Science and Technology Graduate University (OIST))

Quantum reference frames (QRFs) are a universal tool for dealing with symmetries in quantum systems. Roughly speaking, they are internal subsystems that transform in some non-trivial way under the symmetry group of interest and constitute the means for describing quantum systems from the inside in purely relational terms. QRFs are thus crucial for describing and extracting physics whenever no external reference frame for the symmetry group is available. This is in particular the case when the symmetries are gauge, as in gauge theory and gravity, where QRFs arise whenever building physical observables. The choice of internal QRF is typically non-unique, giving rise to a novel quantum form of covariance of physical properties under QRF transformations. This lecture series will explore this novel perspective in detail with a specific emphasis on applications in high-energy physics and gravity. I will begin by introducing QRFs in mechanical setups and explain how they give rise to quantum structures of covariance that mimic those underlying special relativity. I will explain how this leads to subsystem relativity, the insight that different QRF decompose the total system in different ways into gauge-invariant subsystems, and how this leads to the QRF dependence of correlations, entropies, and thermal properties. We will then explore how relational dynamics in Hamiltonian constrained systems and the infamous "problem of time" can be addressed with clocks identified as temporal QRFs. In transitioning to the field theory setting, we will first consider hybrid scenarios, where QRFs are quantum mechanical, but the remaining degrees of freedom are quantum fields including gravitons. I will explain how this encompasses the recent discussion of "observers", generalized entropies, and gravitational von Neumann algebras by Witten et al. and how subsystem relativity leads to the conclusion that gravitational entanglement entropies are observer dependent. We will then discuss the classical analog of QRFs in gauge theory and gravity and how they can be used to build gauge-invariant relational observables and to describe local subsystems. This will connect with discussions on edge and soft modes in the literature, the former of which turn out to be QRFs as well. This has bearing on entanglement entropies in gauge theories, which I will describe on the lattice, providing a novel relational construction that overcomes the challenges faced by previous constructions, which yielded non-distillable contributions to the entropy and can be recovered as the intersection of "all QRF perspectives". Finally, I will describe how the classical discussion of dynamical reference frames can be used to build a manifestly gauge-invariant path integral formulation that opens up novel relational perspectives on effective actions and the renormalization group in gravitational contexts, which is typically plagued by a lack of manifest diffeomorphism-invariance. I will conclude with open questions and challenges in the field. Program: September 24 10:15 - 10:30 Registration and reception with coffee 10:30 - 12:00 Lecture 1 12:00 - 13:30 Lunch 13:30 - 15:00 Lecture 2 15:00 - 16:00 Coffee break 16:00 - 17:00 Lecture 3 17:10 - 18:10 Short talk session 18:20 - 21.00 Banquet September 25 10:15 - 10:30 Morning discussion with coffee 10:30 - 12:00 Lecture 4 12:00 - 13:30 Lunch 13:30 - 15:00 Lecture 5 15:00 - 16:00 Coffee break 16:00 - 17:00 Lecture 6 17:10 - 18:10 Short talk session September 26 10:15 - 10:30 Morning discussion with coffee 10:30 - 12:00 Lecture 7 12:00 - 13:30 Lunch 13:30 - 15:00 Lecture 8 15:00 - 16:00 Coffee break 16:00 - 17:00 Lecture 9 & Closing

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

Event Official Language: English

XIIIth International Symposium on Nuclear Symmetry Energy (NuSym25)

September 8 (Mon) - 13 (Sat) 2025

[Scientific scope] The symposium will address experimental and theoretical investigations of the equation-of-state (EoS) of nuclear matter at various isospin asymmetries. Such investigations include efforts in nuclear structure, nuclear reactions and heavy-ion collisions, as well as in astrophysical observations of compact stars and associated phenomena. An important role of the symposium is to unify efforts of the nuclear physics and astrophysics communities in addressing common research challenges.

Venue: Integrated Innovation Building (IIB)

Event Official Language: English

The 29th MACS Colloquium

July 4 (Fri) 14:45 - 18:00, 2025

Takashi Sakajo (Professor, Division of Mathematics and Mathematical Sciences, Graduate School of Science, Kyoto University)
Shinichi Sasa (Professor, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

14:45-15:00 Teatime discussion 15:00–15:50 Talk by Prof. Takashi Sakajo (Professor, Division of Mathematics and Mathematical Sciences, Graduate School of Science, Kyoto University) 16:00–16:50 Talk by Prof. Shinichi Sasa (Professor, Division of Physics and Astronomy, Graduate School of Science, Kyoto University) 17:15-18:00 Discussion

Venue: Science Seminar House (Map 9), Kyoto University

Event Official Language: Japanese

The 28th MACS Colloquium

April 25 (Fri) 14:45 - 18:30, 2025

Shizuo Kaji (Professor, Institute of Mathematics for Industry, Kyushu University / Professor, Center for Science Adventure and Collaborative Research Advancement (SACRA), Graduate School of Science, Kyoto University)

14:45-15:00 Teatime discussion 15:00-16:00 Talk by Prof. Shizuo Kaji (Professor, Institute of Mathematics for Industry, Kyushu University / Professor, Center for Science Adventure and Collaborative Research Advancement (SACRA), Graduate School of Science, Kyoto University) 16:15-17:20 2024 Study Group introduction session 17:30-18:30 Discussion

Venue: Science Seminar House (Map 9), Kyoto University

Event Official Language: Japanese

MACS 10th Anniversary Colloquium & 2024 MACS Achievement Report Meeting

February 19 (Wed) 14:45 - 18:30, 2025

Hiroshi Kokubu (Executive Vice-President, Kyoto University)
Yoshiko Takahashi (Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University)

14:45-15:00 Teatime discussion [15:00-16:30 First part: MACS 10th Anniversary Colloquium] 15:05-15:05 Opening 15:05-15:30 Talk by Prof. Hiroshi KOKUBU Title: How did MACS begin? Abstract: As the MACS program, which began with a kick-off symposium in May 2016, enters its 10th year in the academic year 2025, I would like to look it back and talk about how it started, what thoughts shared by people involved at the time led to the spirit of MACS. I’d also like to share ideas and experiences in the history of MACS over the past 10 years, including what we wanted to do with MACS in the beginning but could not, or how MACS have collaborated with other subsequent activities of Kyodai RIGAKU (Kyoto U Science). 15:30-15:55 Talk by Prof. Yoshiko TAKAHASHI Title: Excitement through the MACS program Abstract: When the MACS program was launched, a research article was published by Harvard University, in which the gut looping during vertebrate development was beautifully explained by inter-disciplined science with experimental biology, physics, and mathematics. I was very impressed and motivated by this paper, and aimed at similar new waves through the MACS program. I have been running a study group, in which graduate- and undergrad students of not only life science but also physics and mathematics joined, and we enjoyed discussion and looking at real chicken embryos. Such experiences are not what we can easily obtain in conventional education program in campus life. 15:55-16:20 Discussion 16:20-16:30 Break [16:30-18:30 Second part: 2024 MACS Achievement Report Meeting] 16:30-17:30 Flash Talks to report results 17:30-18:30 Poster Session by SG participating students

Venue: Science Seminar House (Map 9), Kyoto University

Event Official Language: Japanese

The 27th MACS Colloquium

November 25 (Mon) 14:45 - 18:00, 2024

Ryusuke Hamazaki (RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team, RIKEN Cluster for Pioneering Research (CPR))
Teruaki Enoto (Associate Professor, Department of Physics, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

14:45-15:00 Teatime discussion 15:00-16:00 Talk by Dr. Ryusuke Hamazaki (RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team) 16:15-17:15 Talk by Dr. Teruaki Enoto (Associate Professor, Department of Physics, Division of Physics and Astronomy, Graduate School of Science, Kyoto University) 17:15-18:00 Discussion

Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research

Event Official Language: Japanese

The 26th MACS Colloquium

July 8 (Mon) 14:45 - 18:00, 2024

Satoshi Taguchi (Professor, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University)
Michitaka Notaguchi (Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University)

14:45-15:00 Teatime discussion 15:00-16:00 Talk by Prof. Satoshi Taguchi (Professor, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University) 16:15-17:15 Talk by Prof. Yoshihiro Morishita (Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University) 17:15-18:00 Discussion

Venue: Science Seminar House (Map 9), Kyoto University

Event Official Language: Japanese

The 25th MACS Colloquium

April 19 (Fri) 14:45 - 18:30, 2024

Wataru Morita (Researcher, Department of Anthropology, National Museum of Nature and Science / Associate Professor, Department of Biological Sciences, Graduate School of Science, The University of Tokyo)

14:45-15:00 Teatime discussion 15:00-16:00 Talk by Dr. Wataru Morita (Researcher, Department of Anthropology, National Museum of Nature and Science / Associate Professor, Department of Biological Sciences, Graduate School of Science, The University of Tokyo) 16:15-17:20 2024 Study Group introduction session 17:30-18:30 Discussion

Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research

Event Official Language: Japanese

The 24th MACS Colloquium

November 20 (Mon) 14:45 - 18:00, 2023

Satoshi Horike (Professor, Department of Chemistry, Graduate School of Science, Kyoto University)
Yoshihiro Morishita (Team Leader, Laboratory for Developmental Morphogeometry, RIKEN Center for Biosystems Dynamics Research (BDR))

14:45-15:00 Teatime discussion 15:00-16:00 Talk by Dr. Satoshi Horike (Professor, Department of Chemistry, Graduate School of Science, Kyoto University) Title: Material science of new glasses of metal-molecular architectures Abstract: The three major materials - ceramics, metals and organic polymers - all form glass phases and underpin our daily lives and industry. Unlike crystals, glasses have a random structure and designing their molecular structures and properties is still a major challenge. In this talk, I will present research on new glasses made of metals and molecules. It will discuss how the glasses are designed and synthesised, as well as the unique glass structures and functions that result from the metal-molecule chemical bonds. 16:15-17:15 Talk by Prof. Yoshihiro Morishita (RIKEN Center for Biosystems Dynamics Research, Team leader) Title: Optimal coding design of positional information and an appropriate spacetime coordinate system to capture an archetype of organ morphogenetic dynamics Abstract: We are engaged in developmental biology research at the intersection of experimentation and theory, driven by a curiosity to understand the laws governing organogenesis. Ideally, we aim to mathematically represent these laws and find commonalities across species and organs. In this seminar, I will present research on a coding design of spatial information within developing tissues, as well as propose spacetime coordinates to directly and quantitatively compare the morphogenetic dynamics of homologous organs across species with different sizes and developmental rates. Furthermore, we will introduce results suggesting the existence of speceis-independent morphogenetic dynamics (a kind of archetype) achieved by applying these methods to biological data. 17:15-18:00 Discussion

Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research

Event Official Language: Japanese

The 23rd MACS Colloquium

July 14 (Fri) 14:45 - 18:00, 2023

Tetsushi Ito (Associate Professor, Division of Mathematics and Mathematical Sciences, Graduate School of Science, Kyoto University)
Aya Ishihara (Professor, International Center for Hadron Astrophysics / Institute for Advanced Academic Research, Chiba University)

14:45-15:00 Teatime discussion 15:00-16:00 Talk by Dr. Tetsushi Ito (Associate Professor, Division of Mathematics and Mathematical Sciences, Graduate School of Science, Kyoto University) 16:15-17:15 Talk by Prof. Aya Ishihara (Professor, International Center for Hadron Astrophysics / Institute for Advanced Academic Research, Chiba University) 17:15-18:00 Discussion

Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research

Event Official Language: Japanese

6th Workshop on Virus Dynamics

July 4 (Tue) - 6 (Thu) 2023

Catherine Beauchemin (Deputy Program Director, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))
Shingo Iwami (Professor, Graduate School of Science, Nagoya University)

The Workshop on Virus Dynamics is an international meeting held every 2 years. It brings virologists, immunologists, and microbiologists together with mathematical and computational modellers, bioinformaticians, bioengineers, virophysicists, and systems biologists to discuss current approaches and challenges in modelling and analyzing different aspects of virus and immune system dynamics, and associated vaccines and therapeutics. This 6th version of the workshop builds on the success of previous ones held in Frankfurt (2013), Toronto (2015), Heidelberg (2017), Paris (2019) and virtually (2021). It is supported by the Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) program at RIKEN, by Nagoya University, and by the Japan Science and Technology Agency. Up-to-date information and registration is available via the website. The workshop is for in-person participation only (no virtual or hybrid option).

Venue: Noyori Conference Hall, Higashiyama Campus, Nagoya University

Event Official Language: English

The 22nd MACS Colloquium

April 28 (Fri) 15:00 - 18:30, 2023

Masaaki Imaizumi (Associate Professor, Graduate School of Arts and Sciences, The University of Tokyo)

15:00-16:00 Talk by Dr. Masaaki Imaizumi (Graduate School of Arts and Science, The University of Tokyo) "Theory of Deep Learning and Overparameterization" 16:15-17:20 2023 Study Group introduction session 17:30-18:00 Discussion

Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research

Event Official Language: Japanese

The 21st MACS Colloquium

November 18 (Fri) 15:00 - 18:00, 2022

Yutaka Yoshikawa (Professor, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University)
Zhaomin Hou (Chief Scientist, Organometallic Chemistry Laboratory, RIKEN Cluster for Pioneering Research (CPR) / Group Director, Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science (CSRS))

15:00-16:00 Talk by Dr. Yutaka Yoshikawa (Division of Earth and Planetary Sciences, Kyoto University) "The Earth Climate and Ocean Surface Waves" 16:15-17:15 Talk by Dr. Zhaomin Hou (Organometallic Chemistry Laboratory, RIKEN Cluster for Pioneering Research / Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science) "New Catalysts, New Reactions and New Functional Materials" 17:15-18:00 Discussion

Venue: via Zoom

Event Official Language: Japanese

The 20th MACS Colloquium

July 8 (Fri) 15:00 - 18:00, 2022

Akira Mori (Associate Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University)
Namiko Mitarai (Associate Professor, Niels Bohr Institute, University of Copenhagen, Denmark)

15:00-16:00 Talk by Dr. Akira Mori "Defense with prey toxins: A snake that has both venomous and poisonous glands" 16:15-17:15 Talk by Dr. Namiko Mitarai "Who "sleeps" and when? Bacterial growth and dormancy" 17:15-18:00 Discussion

Venue: via Zoom

Event Official Language: Japanese

The 19th MACS Colloquium

April 18 (Mon) 15:00 - 17:40, 2022

Yasuhiro Inoue (Professor, Department of Micro Engineering, Graduate School of Engineering, Kyoto University)

15:00- The 19th MACS Colloquium: Talk by Prof. Yasuhiro Inoue "Multicellular Dynamics Simulation of Morphogenesis" 16:05- MACS SG information session 17:10- Individual explanation by each study group (Zoom breakout room)

Venue: via Zoom

Event Official Language: Japanese

The 18th MACS Colloquium

February 14 (Mon) 15:00 - 17:30, 2022

Tetsuya Nagata (Professor, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

15:00- Talk by Prof. Tetsuya Nagata 16:05- 2021 MACS Result Briefing 16:30- Discussion

Venue: via Zoom

Event Official Language: Japanese

The 17th MACS Colloquium

November 19 (Fri) 15:00 - 18:00, 2021

Momoko Hayamizu (Assistant Professor, Faculty of Science and Engineering, School of Fundamental Science and Engineering, Waseda University / PRESTO Researcher, Japan Science and Technology Agency (JST))
Shigeru Kuratani (Chief Scientist, Evolutionary Morphology Laboratory, RIKEN Cluster for Pioneering Research (CPR) / Team Leader, Laboratory for Evolutionary Morphology, RIKEN Center for Biosystems Dynamics Research (BDR))

15:00- Talk by Prof. Momoko Hayamizu 16:15- Talk by Dr. Shigeru Kuratani 17:15- Discussion

Venue: via Zoom

Event Official Language: Japanese

Can social issues be solved by mathematical science? -attempts and challenges

October 26 (Tue) 10:00 - 17:00, 2021

Tetsuo Hatsuda (Program Director, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))
Masato Wakayama (Fundamental Mathematics Research Principal, NTT Institute for Fundamental Mathematics)
Takashi Sakajo (Professor, Division of Mathematics and Mathematical Sciences, Graduate School of Science, Kyoto University)
Shingo Iwami (Professor, Graduate School of Science, Nagoya University)
Hirotaka Irie (Assistant Manager, DENSO Corporation)

In recent years, the importance of mathematical sciences has been increasingly recognized in various fields, as exemplified by the rapid progress of AI technology and the development of DX (Digital Transformation) in companies. In academia, research centers have been established in fields such as space, materials, life, and medicine, where experts in the mathematical sciences play an important role in research activities in their respective fields. At the same time, the universality of mathematics and the quantitative and predictive nature of data analysis are also being considered useful in industry, and some companies are actively using mathematical science in their own business. Some companies are actively utilizing mathematical science in their business. In this symposium, researchers who are conducting research with the mission of returning research using mathematical science to society and implementing it will gather to discuss, based on the results of their cutting-edge research, "Can social issues be solved with mathematical science? -Attempts and Challenges" and discuss the role of mathematical science in society.

Venue: Hybrid Format (Noyori Conference Hall, Nagoya University and Zoom)

Event Official Language: Japanese

The 16th MACS Colloquium

July 5 (Mon) 15:00 - 18:00, 2021

Yoshitaka Tanimura (Professor, Department of Chemistry, Graduate School of Science, Kyoto University)
Hidetoshi Nishimori (Senior Visiting Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) / Specially Appointed Professor, Tokyo Institute of Technology)

15:00- Talk by Prof. Yoshitaka Tanimura 16:15- Talk by Prof. Hidetoshi Nishimori 17:15- Discussion

Venue: via Zoom

Event Official Language: Japanese