122 events in 2024
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Seminar
Dust-driven instabilities in protoplanetary disks: toward understanding formation of planetesimals
January 17 (Wed) at 10:30 - 11:30, 2024
Ryosuke Tominaga (Special Postdoctoral Researcher, Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research (CPR))
Planet formation starts from collisional growth of sub-micron-sized dust grains in a gas disk called a protoplanetary disk. They are expected to grow toward km-sized objects called planetesimals. The resulting planetesimals further coalesce by gravity and form planets. However, there are some barriers preventing planetesimal formation, which includes fast radial drift and collisional fragmentation of dust grains. To circumvent the barriers and to explain planetesimal formation, previous studies have proposed hydrodynamic instabilities of dusty-gas disks. The instabilities can cause dust clumping, and planetesimals form if the resulting clumps collapse self-gravitationally. We have been investigating the linear/nonlinear development of these dust-gas instabilities. We also found a new instability driven by collisional growth of dust, which can bridge a potential gap between the first dust growth and the later planetesimal formation via the previous instabilities. In this talk, I will introduce our work on the dust-driven instabilities and their impact on planetesimal formation.
Venue: Hybrid Format (3F #359 and Zoom), Main Research Building
Event Official Language: English
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Seminar
Does horizontal gene transfer stabilize cooperation in bacteria?
January 16 (Tue) at 16:00 - 17:00, 2024
Anna Dewar (Postdoctoral Researcher, Department of Biology, University of Oxford, UK)
Bacteria are highly social. Much of this sociality occurs through the production of cooperative ‘public goods’. Unlike in animals, bacterial genes are able to transfer horizontally between individuals, in addition to vertically via descendants. This widespread horizontal gene transfer has implications for the concept of relatedness and how cooperation is maintained in bacteria. It has been suggested that horizontal gene transfer, particularly via small segments of DNA called plasmids, could stabilize cooperation in bacteria. Transfer of a cooperative gene could turn non-cooperative ‘cheats’ into cooperators, preventing cheats from invading and destabilizing cooperation. We tested this with a comparative analysis across bacterial species. In contrast to the predictions of the hypothesis, we found that genes for cooperative traits were not more likely to be carried on either: (1) plasmids compared to chromosomes; or (2) plasmids that transfer at higher rates. Our results were supported by theoretical modelling which showed that, while horizontal gene transfer can help cooperative genes initially invade a population, it has less influence on the longer-term maintenance of cooperation.
Venue: via Zoom
Event Official Language: English
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Seminar
Probing structure of neutron stars through X-ray bursters
January 12 (Fri) at 14:00 - 15:15, 2024
Akira Dohi (Special Postdoctoral Researcher, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
Type-I X-ray bursts are rapidly brightening phenomena triggered by the nuclear burning of light elements near the surface of accreting neutron stars. Most of the X-ray bursters show irregular behavior of light curves. However, some X-ray bursters are somehow quite regular, i.e., constant recurrence time and constant shaper of light curves, and are often called Clocked bursters, which are powerful sites to probe uncertainties of many model parameters such as accretion rate, the composition of accreted matter, reaction rates, neutron star structure, and temperature. In this study, we focus on the uncertainties of the equation of states, which determines the latter two properties. Based on our numerical models covering whole areas of neutron stars, we will present their impact on X-ray burst light curves. Furthermore, we will discuss the possibility of constraining the equation of states from Clocked bursters such as GS 1826-24 and 1RXS J180408.9-342058.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Others
Seoul National University student group visit
January 10 (Wed) at 14:00 - 20:00, 2024
Catherine Beauchemin (Deputy Program Director, iTHEMS)
Akinori Tanaka (Senior Research Scientist, RIKEN Center for Advanced Intelligence Project (AIP))
Misako Tatsuuma (Research Scientist, iTHEMS)
Ryo Namba (Senior Research Scientist, iTHEMS)
Dongwook Ghim (Postdoctoral Researcher, iTHEMS)
Steffen Backes (Senior Research Scientist, iTHEMS)A group of 22 undergraduate students in the GLEAP programme at Seoul National University will visit iTHEMS to hear short talks by our members, exchange one-on-one, and visit our facilities. I would like to encourage all available iTHEMS members to take part in this event which will be held in different spaces throughout the day, all at the RIKEN Wako campus Main Research Building: 15:50-16:10 at iTHEMS Common Room (#246-248) Coffee break with iTHEMS members and SNU visitors 16:10-17:50 on 4th floor, room #435-437 Short talks by iTHEMS members 18:05-18:30 in 3rd floor common space Short intro talks by SNU visitors 18:30-20:00 in 3rd floor common space Free informal discussion between SNU visitors and iTHEMS members over some light food [Note some slight changes in the times previously announced]
Venue: 3rd floor public space, Main Research Building / #435-437, Main Research Building / Common Room #246-248
Event Official Language: English
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Seminar
Symmetry Topological field theory for Subsystem symmetry
January 9 (Tue) at 15:00 - 16:00, 2024
Qiang Jia (Research Fellow, School of Physics, Korea Institute for Advanced Study (KIAS), Republic of Korea)
We generalize the idea of symmetry topological field theory (SymTFT) to subsystem symmetry. We propose the 2-foliated BF theory with level N in (3+1)d as subsystem SymTFT for subsystem Z_N symmetry in (2+1)d. Focusing on N=2, we investigate various topological boundaries. The subsystem Kramers-Wannier and Jordan-Wigner dualities can be viewed as boundary transformations of the subsystem SymTFT and are included in a larger duality web from the subsystem SL(2,Z_2) symmetry of the bulk foliated BF theory.
Venue: via Zoom / Seminar Room #359
Event Official Language: English
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Workshop
Functional Renormalization Group at Niigata 2024
January 7 (Sun) - 8 (Mon), 2024
Gergely Fejos (Assistant Professor, Institute of Physics, Eötvös Loránd University, Hungary)
Kenji Fukushima (Professor, Department of Physics, Graduate School of Science, The University of Tokyo)
Kouichi Okunishi (Associate Professor, Faculty of Science, Niigata University)
Junichi Haruna (Ph.D. Student, Graduate School of Science, Kyoto University)
Xu-Guang Huang (Professor, Physics Department and Center for Particle Physics and Field Theory, Fudan University, China)
Katsumi Itoh (Professor, Faculty of Education, Niigata University)
Kiyoharu Kawana (Research Fellow, Korea Institute for Advanced Study (KIAS), Republic of Korea)
Shunsuke Yabunaka (Researcher, Japan Atomic Energy Agency (JAEA))
Takeru Yokota (Special Postdoctoral Researcher, iTHEMS)One of the most fundamental challenges in theoretical physics is to uncover the physical properties of strongly-interacting quantum many-body systems. This problem is shared in both subatomic physics and condensed matter physics; e.g., to unveil ground state structures and dynamical aspects of quantum systems. However, it has been an unresolved issue to establish non-perturbative theoretical tools, which allows a reliable analytic approach to quantum many-body problems described by field theory. The Functional Renormalization Group (FRG) is proposed as one of the theoretical methods that facilitates the non-perturbative investigation of quantum many-body systems. The FRG has found applications in various fields of physics, ranging from particle and nuclear physics to condensed matter physics, leading to several unique achievements in each fields. The aim of this two-day workshop is to provide an overview of the recent applications and progress of FRG in various fields of physics, discuss future directions, and explore potential new collaborations that bridge different fields of physics.
Venue: Kaishi Professional University Yoneyama Campus (Main Venue) / via Zoom
Event Official Language: English
122 events in 2024