Volume 343
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Seminar Report
Pebbles in Planet Formation on February 10-13, 2025
2025-02-20
From February 10 to 13, the workshop "Pebbles in Planet Formation" featured a diverse range of topics, including dust theory, solar system small body exploration, dust experiments, simulations of planetesimal formation via instabilities, and observations of protoplanetary disks. The program included six keynote talks, 40 contributed talks, and 18 poster presentations.
Ample time was allocated for coffee breaks and discussion sessions, fostering in-depth conversations on various topics. In particular, the workshop reaffirmed the importance of collaboration between experimental groups in Germany and experimental and theoretical groups in Japan. As a result, we have established a foundation for ongoing communication and future cooperation.
Reported by Misako Tatsuuma
Pebbles in Planet Formation
February 10 (Mon) - 13 (Thu), 2025
Upcoming Events
Workshop
Asymptotics in astrophysics iTHEMS workshop
February 25 (Tue) - 28 (Fri), 2025
This workshop will include overview talks of application of asymptotics and perturbation theory techniques in (wave transport or oscillation related) astrophysics and cosmology eigenvalue problems. In addition, there will be introductory talks about fundamental asymptotics and perturbation theory techniques used in theoretical physics.
The purpose of this interdisciplinary workshop is to identify problems in astrophysics and related fields including, but not limited to, stellar structure and evolution, black holes and high-energy physics which can be solved using existing asymptotics and perturbation theory methods in theoretical physics problems (e.g. quantum field theory, gravity), and vice versa.
It will also feature hands-on Mathematica or Python tutorials which demonstrate:
- practical use of WKB methods
- resummation methods and resurgence
- deriving black hole quasinormal modes
- deriving normal modes in stars
- reducing numerical artefacts in hydrodynamics solvers
by examples.
Venue: 8F, Integrated Innovation Building (IIB), Kobe Campus, RIKEN
Event Official Language: English
Seminar
RIKEN Quantum Seminar
Quantum-Centric Supercomputing Software
February 26 (Wed) at 13:00 - 14:00, 2025
Hanhee Paik (Head of IBM Quantum Japan, IBM Quantum)
A quantum-centric supercomputer represents the next generation of computing, combining a quantum computer with a classical supercomputer. It leverages error mitigation and error correction techniques to deliver results within practical timeframes. When fully developed, this system relies on advanced middleware to seamlessly integrate quantum circuits with classical computing resources. In this presentation, we will introduce IBM Quantum’s middleware for quantum-centric supercomputers, highlighting collaborative projects with our research partners.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Seminar
iTHEMS Biology Seminar
Genome and Sex Chromosome Analyses of Japanese Frogs Carrying Both XY and ZW Chromosomes Within the Same Species
February 27 (Thu) at 16:00 - 17:00, 2025
Yukako Katsura (Assistant Professor, Center for the Evolutionary Origins of Human Behavior, Kyoto University)
The evolution of sex chromosomes, particularly sex chromosome turnover, is a complex and fascinating topic in genetics and evolutionary biology. Sex chromosome turnover refers to the process in which the sex chromosome system changes from XY to ZW (or vice versa), or in which sex chromosomes with different evolutionary origins emerge within the same system (e.g., from one XY system to another XY system). To study sex chromosome turnover, we focus on the Japanese frog (Glandirana rugosa), which possesses both XY and ZW sex chromosomes within the same species, and investigate the molecular mechanisms behind the turnover in the frog (Review: Hayashi et al. JB 2024). Previously, we sequenced the nuclear genome of the ZZ frog (Katsura et al. LSA 2021) and identified sex-linked genes in two populations of the XY and ZW frogs (Miura et al. Mol Ecol 2022). It has been suggested that sex chromosomes originating from at least three different chromosomal lineages have independently emerged within this species. The frogs have a total of 13 chromosomes, and in two populations (Tokai/Eastern Central Japan and Hokuriku-Tohoku/North-Western Japan), chromosome 7 has morphologically differentiated into both ZW and XY chromosomes. However, in other populations, sex chromosomes do not show any morphological differentiation. In this seminar, I introduce the background of our sex chromosome study and present the results of sequence comparisons of morphologically differentiated XY and ZW chromosomes, as well as findings from our analyses of populations, genome, and transcriptome.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359, 3F Main Research Building, RIKEN
Event Official Language: English
Seminar
iTHEMS Seminar
Applications of Geometry of Numbers to Phyllotaxis and Crystallography
February 28 (Fri) at 14:00 - 15:30, 2025
Ryoko Oishi-Tomiyasu (Professor, Institute of Mathematics for Industry, Kyushu University)
The golden angle method, originally known from phyllotaxis in botany, has been used to generate dense point packings on surfaces of revolution. In my recent work, I have extended this method to general surfaces and higher-dimensional manifolds by employing the theories of products of linear forms in number theory, diagonalizable metrics in differential geometry, and local solutions of quasilinear hyperbolic equations. This extension suggests that any biological forms can exhibit phyllotactic patterns locally regardless of their morphology, while the overall pattern is influenced by their global properties in the embedded space. On the algebraic side, it is interesting that the same ideas used for phyllotaxis can also be applied to pseudorandom number generation over F2 = {0, 1}.
This work is motivated by my previous research in crystallography. Time permitting, I will also introduce some of the research, which contributes to the analytical foundations of crystallography and is also an application of the geometry of numbers.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Workshop
RIKEN-Nara Women's University Joint Diversity Promotion Workshop 2025
March 3 (Mon) - 4 (Tue), 2025
The RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) and the Faculty of Science at Nara Women's University are promoting a project to foster female researchers under the auspices of the RIKEN Diversity Promotion Office. As part of the program, 19 undergraduate and graduate students from Nara Women's University will visit several laboratories on the RIKEN Wako campus to ask questions about their research and hold workshops/presentations with iTHEMS researchers.
Organizers:
RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS)
Faculty of Science, Nara Women's University
Program:
13:50-15:15
RIBF Facility, RIKEN Nishina Center (RNC) (E01, Nishina RIBF Building)
15:30-16:30
RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) (C01, Main Research Building, #359)
Introduction to iTHEMS: Tetsuo Hatsuda (iTHEMS Director)
Lecture and Q&A: Nagisa Hiroshima (iTHEMS)
16:45-18:00
RIKEN Center for Brain Science (CBS) (C56, Ikenohata Research Building, #316)
Laboratory for Sensorimotor Integration (Fumi Kubo, Team Leader)
18:30-21:00
Networking Session (C01, Research Building 3F)
9:15-10:30
RIKEN Center for Advanced Photonics (RAP) (C32, Laser Research Building, Mid Conference Room A)
Photonics Control Technology Team (Satoshi Wada, Team Leader)
10:45-12:00
RIKEN Center for Sustainable Resource Science (CSRS) (S01, Biological Science Research Building, S311)
Molecular Bioregulation Research Team (Shinya Hagihara, Team Leader)
Venue: RIKEN Wako Campus
- RIBF Facility, RIKEN Nishina Center (RNC)
- RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS)
- Laboratory for Sensorimotor Integration, RIKEN Center for Brain Science (CBS)
- Photonics Control Technology Team, RIKEN Center for Advanced Photonics (RAP)
- Molecular Bioregulation Research Team, RIKEN Center for Sustainable Resource Science (CSRS)
Workshop
iTHEMS Cosmology Forum 3 - (P)reheating the primordial Universe
March 4 (Tue) - 5 (Wed), 2025
Seishi Enomoto (Postdoctoral Researcher, College of Engineering Science, Yokohama National University)
John T. Giblin (Professor, Department of Physics, Kenyon College, USA)
Kyohei Mukaida (Assistant Professor, Theory Center, High Energy Accelerator Research Organization (KEK))
iTHEMS Cosmology Forum Workshop is a series of short workshops, each focusing on an emerging topics in cosmology. The target audience is cosmologists, high-energy physicists and astronomers interested in learning about the subject, not just those who have already worked on the topic. The goal of the workshop is to provide working knowledge of the topic and leave dedicated time for discussions to encourage mutual interactions among participants.
The third workshop is devoted to the 'reheating' phase of the early Universe. Reheating bridges the gap between the (almost) empty universe at the end of cosmic inflation and the thermal state of particles, required for Big-Bang nucleosynthesis, and the events of the hot Big-Bang model as a whole, to unfold. It is expected to proceed in different stages starting with a violent parametric resonant creation of particles, dubbed preheating, followed by a redistribution of energy leading to a thermal state. This phase potentially hosts rich phenomenology such as the formation of topoligical defects e.g. solitons, generation of gravitiational wave, and so on. Yet, the very non-linear nature of reheating makes it notoriously hard to describe analytically, and even numerical simulations struggle to follow the whole sequence of events in a given model. Reheating studies have thus yet to reach the degree of compherensiveness and universality that the understanding of cosmic inflation has achieved.
This forum will consist of two events. The first, on March 4th, will be in conference format comprising scientific talks on research trends in (P)Reheating. The second, on March 5th, will be a tutorial on numerical aspects of reheating (both theory and hands-on with code) hosted by Tom Giblin of Kenyon College.
The workshop will be in English.
The workshops are organised by the iTHEMS Cosmology Forum working group, which is the successor of the Dark Matter Working Group at RIKEN iTHEMS.
Important dates:
Feb. 25th - Registration deadline
March 4th - Workshop Day (Room #435-437, Main Research Building 4F)
March 5th - Tutorial Day (Room #445-447, Main Research Building 4F)
Invited Speakers:
John T. Giblin - Kenyon College
Kyohei Mukaida - KEK
Seishi Enomoto - Yokohama National University
Organisers:
Kohei Hayashi, Nagisa Hiroshima, Derek Inman, Amaury Micheli, Ryo Namba
Venue: #435-437, 4F, Main Research Building, RIKEN / #445-447, 4F, Main Research Building, RIKEN
Event Official Language: English
Colloquium
iTHEMS Colloquium
Smart heuristics of a single-celled organism
March 7 (Fri) at 14:00 - 15:30, 2025
Toshiyuki Nakagaki (Professor, Research Institute for Electronic Science, Hokkaido University)
Although we rarely question how smart unicellular organisms are, it has become clear that unicellular organisms are smarter than we expected. In fact, various protozoa (unicellular eukaryotes) can take actions that are advantageous for their survival even in complex environments in the wild environments. In this talk, I will introduce some typical examples of smart behaviors in a protozoan amoeba (the plasmodium of Physarum polycephalum): (1) maze-solving, (2) formation of multi-functional transport network that mimics public transportation network among cities in Tokyo region, and so on. We will propose a mathematical model of these behaviors and extract the heuristics (simple rules of behavior) that give rise to their smartness. In general, we will discuss the future potential of research into the behavioral intelligence of protozoa.
References
- Research Project “Ethological Dynamics in Diorama Environments”
- Toshiyuki Nakagaki, Hiroyasu Yamada & Ágota Tóth, Maze-solving by an amoeboid organism, Nature 407, 470 (2000), doi: 10.1038/35035159
- Atsushi Tero, Seiji Takagi, Tetsu Saigusa, Kentaro Ito, Dan P. Bebber, Mark D. Fricker, Kenji Yumiki, Ryo Kobayashi, and Toshiyuki Nakagaki, Rules for Biologically Inspired Adaptive Network Design, Science 327(5964):439-42 (2010), doi: 10.1126/science.1177894
- John S. MacNeil, Slimy, But Not Stupid
- Philip Ball, Cellular memory hints at the origins of intelligence, Nature volume 451, 385 (2008), doi: 10.1038/451385a
- Steve Nadis, Slime and fleas feature in Ig Nobel awards, Nature volume 455, pages 714–715 (2008), doi: 10.1038/455714b
- Pete Wilton, Ig Nobel for slime networks
- Ferris Jabr, How Brainless Slime Molds Redefine Intelligence [Video]
Venue: Okochi Hall, 1F Laser Science Laboratory, RIKEN / via Zoom
Event Official Language: English
Workshop
Third Workshop on Density Functional Theory: Fundamentals, Developments, and Applications (DFT2025)
March 25 (Tue) - 27 (Thu), 2025
The density functional theory (DFT) is one of the powerful methods to solve quantum many-body problems, which, in principle, gives the exact energy and density of the ground state. The accuracy of DFT is, in practice, determined by the accuracy of an energy density functional (EDF) since the exact EDF is still unknown. Currently, DFT has been used in many communities, including nuclear physics, quantum chemistry, and condensed matter physics, while the fundamental study of DFT, such as the first principle derivations of an accurate EDF and methods to calculate many observables from obtained densities and excited states, is still ongoing. However, there has been little opportunity to have interdisciplinary communication.
On December 2022, we had the first workshop on this series (DFT2022) at Yukawa Institute for Theoretical Physics, Kyoto University, and several interdisciplinary discussions and collaborations were started. On February 2024, we had the second workshop on this series (DFT2024) at RIKEN Kobe Campus, and more stimulated discussion occured. To keep and extend collaborations, we organize the third workshop. Since the third workshop, we extend the scope of the workshop to the development and application of DFT as well. In this workshop, the current status and issues of each discipline will be shared towards solving these problems by meeting together among researchers in mathematics, nuclear physics, quantum chemistry, and condensed matter physics.
This workshop mainly comprises lectures/seminars on cutting-edge topics and discussion, while sessions composed of contributed talks are also planned.
Venue: 8F, Integrated Innovation Building (IIB), Kobe Campus, RIKEN / via Zoom
Event Official Language: English
Seminar
Quantum Gravity Gatherings
Stability of nonsingular black holes
March 27 (Thu) at 15:00 - 16:30, 2025
Shinji Tsujikawa (Professor, Graduate School of Advanced Science and Engineering, Faculty of Science and Engineering, Waseda University)
We show that nonsingular black holes (BHs) realized in nonlinear electrodynamics are always prone to Laplacian instability around the center because of a negative squared sound speed in the angular direction. This is the case for both electric and magnetic BHs, where the instability of one of the vector-field perturbations leads to enhancing a dynamical gravitational perturbation in the even-parity sector. Thus, the background regular metric is no longer maintained in a steady state. We also generalize our analysis to the case in which a scalar field is present besides the U(1) gauge field and find no explicit examples of linearly stable nonsingular BHs. Our results suggest that the construction of regular BHs without instabilities is generally challenging within the scheme of classical field theories.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Seminar
iTHEMS Seminar
Artificial Intelligence and Neuroscience
April 11 (Fri) at 14:00 - 15:30, 2025
Junichi Chikazoe (Professor, Center for Brain,Mind and KANSEI Sciences Research, Hiroshima University)
Recent advancements in artificial intelligence have led to various discoveries in the field of neuroscience. For example, it has been demonstrated that the information on orientation columns in the visual cortex and the basic taste information in the gustatory cortex can be extracted by applying machine learning to relatively low-resolution functional MRI data. Additionally, intriguing findings have emerged, such as the information processing structures of artificial neural circuits—designed independently of the brain—showing similarities to those of biological neural networks.
In this talk, I will discuss the applications of artificial intelligence in neuroscience and explore future directions in this field.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Upcoming Visitors
February 24 (Mon) - 25 (Tue), 2025 Gokcumen OmerProfessor, Department of Biological Sciences, University at Buffalo, USA Visiting Place: RIKEN Wako Campus |
February 24 (Mon) - 28 (Fri), 2025 Nobuo IidaPostdoctoral Fellow, Department of Mathematics, School of Science, Institute of Science Tokyo Visiting Place: RIKEN Wako Campus |
February 24 (Mon) - 28 (Fri), 2025 Keita GotoPostdoctoral Fellow, National Taiwan University, Taiwan Visiting Place: RIKEN Wako Campus |
Paper of the Week
Week 4, February 2025
2025-02-20
Title: Systematic study of the composition of Type I X-ray burst ashes: Neutron star structure v.s. Reaction rate uncertainties
Author: Guoqing Zhen, Helei Liu, Akira Dohi, Guoliang Lü, Nobuya Nishimura, Chunhua Zhu, Renxin Xu
arXiv: 2502.10992
Title: Chiral symmetry restoration in QC_2D from effective model using the functional renormalization group
Author: G. Fejos, D. Suenaga
arXiv: 2502.10134
Title: Birational Transformations and 2d (0,2) Quiver Gauge Theories beyond Toric Fano 3-folds
Author: Dongwook Ghim, Minsung Kho, Rak-Kyeong Seong
arXiv: 2502.08741
Title: Numerical evidence for a CP broken deconfined phase at θ=π in 4D SU(2) Yang-Mills theory through simulations at imaginary θ
Author: Mitsuaki Hirasawa, Masazumi Honda, Akira Matsumoto, Jun Nishimura, Atis Yosprakob
arXiv: 2502.09115
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