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Workshop In Session
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.
Venue: 8F, Integrated Innovation Building (IIB)
Event Official Language: English
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Seminar Today
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
Event Official Language: English
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Seminar Tomorrow
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: #359, 3F, Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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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
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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 / #445-447, 4F, Main Research Building
Event Official Language: English
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Seminar
From the Andes to the Lab Bench: Genomic, Evolutionary, and Functional Insights into Amylase Gene Variation and Metabolic Adaptation
March 6 (Thu) at 16:00 - 17:00, 2025
Gokcumen Omer (Professor, Department of Biological Sciences, University at Buffalo, USA)
Our laboratory investigates how genomic structural variations (SVs) uniquely drive biological diversity and evolution, surpassing smaller-scale variations like single nucleotide polymorphisms. This talk highlights our work on the amylase locus, a rapidly evolving genomic region shaped by dietary adaptations, frequent duplications, and high mutation rates. I will discuss its convergent evolution across mammals, driven by natural selection linked to starch-rich diets, and describe how long-read sequencing uncovered the mutational mechanisms behind its rapid evolution. We also examine local positive selection in indigenous Andean populations with historically starch-rich diets and how these adaptations impact metabolic health. Finally, I will summarize functional experiments in transgenic mice and diabetic-prone Western Nile rats, relevant models for human metabolism, to investigate the broader metabolic roles of amylase gene duplications. This research provides a roadmap for studying complex SVs in evolution, offering insights into human adaptation and health.
Venue: via Zoom / Seminar Room #359
Event Official Language: English
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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.
Venue: Okochi Hall (Main Venue) / via Zoom
Event Official Language: English
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Conference
Meeting for Intersections of Nuclear and Other Researches
March 10 (Mon) - 11 (Tue), 2025
The purpose of this workshop (held in Japanese) is to promote interdisciplinary research by young researchers through exchanges among all fields of theoretical physics, including the nuclear physics, which is a boundary region between various fields.
Venue: #435-437, Main Research Building
Event Official Language: Japanese
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Seminar
RIKEN Quantum hands-on workshop on QURI SDK for creating and executing quantum algorithms on various quantum computers and simulators
March 13 (Thu) at 15:00 - 17:30, 2025
This workshop will be a hands-on session on QURI SDK, following the RIKEN Quantum seminar by Andreas Thomasen (QunaSys) on January 27. Even if you did not attend the previous seminar, please join us if you would like to learn how to use QURI SDK.
Venue: #359, 3F, Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
It’s about time! Daily rhythms in malaria infections matter for parasite survival and transmission
March 13 (Thu) at 17:00 - 18:00, 2025
Reece Sarah (Professor, University of Edinburgh, UK)
The Reece lab provides a unique perspective on parasites, examining their world within hosts and vectors (insects that transmit parasites). Working at the intersection of parasitology, chronobiology, and evolutionary ecology, our research asks: “what makes a successful parasite” and “what are their evolutionary limits”? Unlike most infection research, that focuses solely on genetics and molecular aspects, our approach considers parasites in their ecological and evolutionary contexts. This has enabled us to uncover the sophisticated strategies that malaria parasites possess, such as optimizing the balance between transmission and replication, strategic investment in each sex of transmission stages, and scheduling activities according to the time of day. By understanding how parasites navigate their challenging lifestyles and seize opportunities, we contribute to interventions that can outsmart parasites and reduce the risk of resistance evolution. Our findings extend beyond the laboratory, showcasing the potential of environmental research to curb the impact of parasitic infections, whether in humans, wildlife, livestock, or agriculture, and helping to protect ecosystems.
Venue: via Zoom
Event Official Language: English
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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) / via Zoom
Event Official Language: English
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Seminar
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 (Main Venue) / via Zoom
Event Official Language: English
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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: #359 3F, Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English