Theoretical analysis of High-dose/Refuge strategy for durability of pest control

November 21 (Thu) at 16:00 - 17:00, 2024

Sayaki Suzuki (Postdoctoral Researcher, Research Center for Integrative Evolutionary Science, The Graduate University for Advanced Studies)

When using chemicals to control pathogens or pests, a problem that always arises is that parasites develop resistance to the chemicals. In many cases, the amount of chemical used must be reduced for using the chemicals sustainably. However, if certain conditions are met, a method is known that can suppress the development of resistance in diploid organisms such as pest insects. This is the high-dose/refuge strategy (HD/R) proposed by Comins (1977). This unique method combines high doses of pesticide spraying with ‘Refuge’ that are completely pesticide-free, and is a rare example of a successful method that actually fields. In this presentation, I will provide an overview of the HD/R strategy, a formulation that incorporates the entire life cycle of the insect, which was an issue that Comins had not yet resolved. And show the life cycle of the insect and the conditions under which the HD/R strategy is effective, based on the results of an approximation using a source-think model.

Venue: via Zoom

Event Official Language: English

Nuclear clustering phenomena revealed by knockout reaction

November 20 (Wed) at 15:30 - 17:00, 2024

Kazuki Yoshida (Assistant Professor, Research Center for Nuclear Physics, Osaka University)

Nuclear clustering is one of the unique phenomena in the nucleon many-body system. Historically, alpha formation has been known since the very early years of the nuclear physics, in the light and heavy mass regions. The former is known as the alpha clustering and its threshold rule, which was introduced by the Ikeda diagram in 1968. The latter has been known since the beginning of the nuclear physics as the alpha decay phenomena; the formation of alpha particles and their tunneling through the Coulomb barrier. Recently, the alpha clustering has been experimentally confirmed in the medium mass nuclei, 112-124Sn (Tin isotopes), using the alpha knockout reaction. Triggered by the experimental observation, the alpha knockout reaction is used as a reaction probe for the alpha clustering phenomena. In this talk, I will give an overview of the clustering phenomena and its reaction observables, in particular I will introduce the idea that the alpha knockout reaction can be a probe for the alpha formation on the alpha decay nuclei. In general, this idea can be applied to probe the particle trapped in the potential resonance.

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

Event Official Language: English

Machine learning applications in neutron star physics

November 19 (Tue) at 15:00 - 16:30, 2024

Márcio Ferreira (Researcher, Physics Department, University of Coimbra, Portugal)

The equation of state and the internal composition of a neutron star are still unanswered questions in astrophysics. To constrain the different composition scenarios inside neutron stars, we rely on pulsars observations and gravitational waves detections. This seminar shows different applications of supervised/unsupervised machine learning models in neutron stars physics, such as: i) extract the equation of state; ii) infer the proton fraction; iii) detect the possible existence of a second branch in the mass-radius diagram; and iv) detect the presence of hyperons. Márcio Ferreira is a researcher at the Center for Physics at the University of Coimbra, Portugal, focusing on the application of machine learning to astrophysics and materials science. His work utilizes generative and descriptive models to address key questions in these fields. With a PhD in high energy physics and a Master’s in quantitative methods for finance, Márcio also merges his expertise in physics with an interest in financial market dynamics.​

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

Event Official Language: English

Entanglements & Applications

November 18 (Mon) at 9:30 - 15:00, 2024

Myfanwy Evans (Professor, Institute of Mathematics, University of Potsdam, Germany)
Stephen Hyde (Emeritus Professor, Materials Physics, Australian National University, Australia)
Toky Andriamanalina (Ph.D. Student, Institute of Mathematics, University of Potsdam, Germany)

9:30-10:30: Toky Andriamanalina Title: Untangling 3-periodic entanglements of filaments and nets Abstract: Entanglements of curves and nets can used to describe various biological and chemical structures, such as coordination polymers, liquid crystals, or DNA origami crystals. We recently developed new diagrammatic descriptions of 3-periodic entanglements. These new diagrams are drawn out of a projection along one axis of a unit cell of a 3-periodic structure. By using these diagrams, we define the notion of untangling number for 3-periodic structures, which is a measure of complexity of the entanglement. Thanks to this, it is now possible to characterise the least tangled structures that we call ground states, and in particular we show that the rod packings are the generic ground states of entanglements of curves. 10:30-11:00: coffee break 11:00 - 12:00: Stephen Hyde Title: Tangles... and untangles Abstract: Knots, braids, links, self-entangled nets, multiple catenated infinite nets... are examples of what we call, simply, “tangles”. They are relevant to molecular-scale (bio)materials, from duplexed ssRNA to metal-organic frameworks. We are interested in understanding: 1.Which tangles are “simple”? 2.How tangled is a tangle!? Our tangle toolkit is a simple one: we assemble helices into networks, allowing a broad spectrum of tangles to be built, from knots to tangled nets. Interesting “simple” tangles are entanglements of the edges of Platonic polyhedra [1] and entangled 2-periodic nets [2]. A proposed answer to point 2. above will be discussed. if there is time. The ideas are at present largely unpublished, and being working into a book to be published, we hope, in late 2025 [3]. 13:00 - 14:00: Myfanwy Evans Title: Can solvents tie knots? Helical folds of biopolymers in liquid environments. Abstract: Using a simulation technique based on the morphometric approach to solvation, we performed computer experiments which fold a short open flexible tube, modelling a biopolymer in aqueous environments, according to the interaction of the tube with the solvent alone. We find an array of helical geometries that self-assemble depending on the solvent conditions, including symmetric double helices where the strand folds back on itself and overhand knot motifs. Interestingly these shapes—in all their variety—are energetically favoured over the optimal helix. By differentiating the role of solvation in self–assembly our study helps illuminate the energetic background scenery in which all soluble biomolecules live. This event is organized with the Interdisciplinary Math Study Group.

Venue: Seminar Room #359

Event Official Language: English

iTHEMS Science Outreach Workshop 2024

November 15 (Fri) - 17 (Sun), 2024

This year's meeting on "Outreach of RIKEN iTHEMS 2024@Sendai&Zoom" will be held from FRI November 15 to SUN November 17, as a face-to-face meeting at TOKYO ELECTRON House of Creativity of Tohoku Forum for Creativity in cooperation with iTHEMS SUURI-COOL (Sendai) using ZOOM for the necessary part as well.

Venue: TOKYO ELECTRON House of Creativity, Katahira Campus, Tohoku University (Main Venue) / via Zoom

Event Official Language: Japanese

Finding Rules for Condensation of Disordered Protein Sequences

November 14 (Thu) at 16:00 - 17:00, 2024

Kyosuke Adachi (Research Scientist, iTHEMS)

Event Official Language: English

Emergence of wormholes from quantum chaos

November 12 (Tue) at 16:30 - 18:00, 2024

Gabriele Di Ubaldo (Postdoctoral Researcher, iTHEMS)

I will give a broad introduction to some aspects of quantum gravity and the so-called black hole information problem. I will introduce wormholes as novel contributions to the gravitational path integral and how they provide a solution to the black hole information problem. Wormholes, however, are rather mysterious and we don’t have a good microscopic understanding of them and why we should include them in the our theory. In particular, wormholes seem to imply that gravity is not a proper quantum system but rather an average over a statistical ensemble of quantum systems. I will then transition into my own work which addresses these questions in the context of holography. I will show how wormholes in 3D quantum gravity can emerge from quantum chaos in the dual 2D Conformal Field Theory, without averaging. Wormholes capture coarse-grained properties of the CFT and conversely an individual chaotic CFT can effectively behave as an averaged system. Furthermore we will be able to explicitly factorize wormholes to extract microscopic information on black hole microstates. To achieve this I will (briefly) introduce and use tools such as Random Matrix Theory, the Gutzwiller Trace formula and Berry’s diagonal approximation, and the theory of SL(2,Z) non-holomorphic modular forms.

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

Event Official Language: English

Forming primordial black holes

November 11 (Mon) at 14:00 - 15:30, 2024

Zachary Picker (Postdoctoral Researcher, University of California, Los Angeles, USA)

Primordial black holes (PBHs) are black holes which form in the early universe. Not only are PBHs good dark matter candidates, but they have a wide range of fascinating phenomenology (even if they are only a fraction of the dark matter). In this talk I will review a somewhat under-discussed aspect of the PBH gospel---their formation mechanisms. In fact, there is a wide variety of ways to form PBHs of different sizes and abundances, and many of our favorite BSM theories can have PBHs in their spectra. I will then discuss some of our particular upcoming research on PBH formation, where attractive Yukawa forces in a dark sector can lead to the early formation of dense dark structures called Fermi balls which can collapse to black holes, with novel cosmological implications.

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

Event Official Language: English

Mathematical modeling of circadian rhythm: temperature compensation and after effect

November 7 (Thu) at 16:00 - 17:00, 2024

Yuta Kitaguchi (Ph.D. Student, Graduate School of Natural Science & Technology, Kanazawa University)

Almost all organisms have a circadian clock. This circadian clock consists of negative transcriptional-translational feedback loops (TTFLs) between various circadian clock genes in cells. Collective gene expression rhythms in the central circadian pacemaker tissue regulate nearly 24-hour behavioral rhythms of organisms. The circadian clock has three characteristics: (1) autonomous oscillation, (2) temperature compensation of the period, and (3) entrainment to external cycles such as a light-dark cycle. In this presentation, I will talk about theoretical studies on temperature compensation, and the entrainment to light-dark cycles. For temperature compensation, I will show that only a few temperature-insensitive reactions in the complex TTFLs of the circadian clock are sufficient to maintain the circadian period under increasing temperature. For entrainment to the light-dark cycle, I will show the mechanism for after-effect where the period of the circadian clock in constant darkness correlates with that of a previously entrained light-dark cycle for several months.

Venue: via Zoom

Event Official Language: English

The 6th Special Online Class for Junior and Senior High School Students: Hot Science in Kobe Right Now

November 2 (Sat) at 10:30 - 14:30, 2024

Genshiro Sunagawa (Team Leader, Laboratory for Hibernation Biology, RIKEN Center for Biosystems Dynamics Research (BDR))
Kento Sato (Team Leader, High Performance Big Data Research Team, RIKEN Center for Computational Science (R-CCS))
Kyosuke Adachi (Research Scientist, iTHEMS)
Safiye Esra Sarper (Special Postdoctoral Researcher, Laboratory for Developmental Morphogeometry, RIKEN Center for Biosystems Dynamics Research (BDR))

The RIKEN conducts a wide variety of research. In this session, four researchers working at the Kobe Campus in the fields of mathematical science, information science, and biology will present their work. From iTHEMS, Research Scientist Kyosuke Adachi will introduce his research, which aims to uncover the mechanisms of collective motion using physics and computers. For those interested in participating, please check the event website via the related link for instructions on how to attend.

Venue: via Zoom

Event Official Language: Japanese

Knitting Day

November 1 (Fri) at 10:00 - 16:00, 2024

Tomohiko Sano (Senior Assistant Professor, Department of Mechanical Engineering, Faculty of Science and Technology, Keio University)
Samuel Poincloux (Assistant Professor, Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University)
Taiki Goto (Master's Student, Keio University)
Daisuke Shimamoto (Master's Student, The University of Tokyo)
Kotone Tajiri (Master's Student, Keio University)
Sonia Mahmoudi (Assistant Professor, Mathematical Science Group, Advanced Institute for Materials Research (AIMR), Tohoku University)

The 'Knitting Day' event is a one-day gathering that brings together students and researchers from diverse fields to explore the fascinating connections between the topology and mechanics of knitting. It aims to foster interdisciplinary discussions on how knitting techniques can be understood through mathematical, physical, and engineering lenses and their potential applications in industry. This event is organized with the Interdisciplinary Math Study Group. Schedule: 10:00 – 10:30: Welcome coffee 10:30 – 11:00: Samuel Poincloux 11:10 – 11:30: Kotone Tajiri 11:30 – 12:00: Discussion 12:00 – 13:00: Lunch 13:00 – 13:30: Daisuke Shimamoto 13:40 – 14:00: Taiki Goto 14:00 – 14:30: Discussion 14:30 – 15:10: Sonia Mahmoudi 15:10 – 16:00: Discussion & Coffee Break 16:00-18:00: Internal Discussion From 18:00: Dinner Titles: Taiki Goto: Twist deformation in trefoil knot Sonia Mahmoudi: A new topological model of knitting Samuel Poincloux: Knit mechanics and frictional troubles Daisuke Shimamoto: TBA Kotone Tajiri: Curling morphology of knitted fabrics: structure and mechanics

Venue: #345-347, 3F, Main Research Building

Event Official Language: English

Heterostyly and the evolution of mating system in plants

October 31 (Thu) at 16:00 - 17:00, 2024

Jeffrey Fawcett (Senior Research Scientist, iTHEMS)

Many organisms exhibit various strategies to avoid self-fertilization and promote outcrossing (mating with different individuals). Such strategies have repeatedly evolved and been disrupted throughout evolution, resulting in a remarkable diversity of mating systems. The most well-known strategy is sexual dimorphism, in which mating is only successful between opposite sexes (e.g. male and female) which exhibit different morphology (e.g. males and females look different). However, some plants, including buckwheat that I have been studying, have evolved a strategy where all individuals either have flowers with long or short styles (female organ), referred to as heterostyly or distyly, and mating is typically only successful between individuals with long-styled flowers and those with short-styled flowers, i.e., outcrossing is promoted by floral dimorphism that is not associated with sexes. While how such a system evolves and its genetic basis are still largely unknown, the genomic region responsible for heterostyly has been identified in many different species within the past year or two, revealing some interesting parallels between independently evolved systems. In this seminar, I will introduce these recent findings and discuss how heterostyly may be linked to the diverse mating systems observed in plants. I will also introduce what we have been doing and are planning/hoping to do in buckwheat and its related species.

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

Event Official Language: English

Quantum signature kernels

October 30 (Wed) at 14:00 - 15:00, 2024

Samuel Crew (Postdoctoral Fellow, Imperial College London, UK)

Arising from rough path theory, the signature transform captures features of time-series data by constructing a so-called path signature. This feature has proven valuable for various machine learning tasks. However, computing the associated signature kernel classically remains computationally intensive. In this talk, I will present recent developments in generalising the signature kernel to randomised Lie group path developments. I will discuss a quantum approach via matrix models with an associated unitary quantum signature kernel to propose a quantum algorithm for its computation.

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

Event Official Language: English

Holographic Gubser flow

October 29 (Tue) at 13:30 - 14:30, 2024

Sukrut Mondkar (Postdoctoral Researcher, Harish-Chandra Research Institute, India)

Gubser flow is an evolution with cylindrical and boost symmetries, which can be best studied by mapping the future wedge of Minkowski space ℝ^{(3,1)} to dS_3 × ℝ in a conformal relativistic theory. Here, we sharpen the analytic results of Banerjee, Mitra, Mukhopadhyay Soloviev, EPJC (2024) and validate them via the first numerical exploration of the Gubser flow in a holographic conformal field theory. Remarkably, the leading generic behavior at large de Sitter time is free-streaming in transverse directions and the sub-leading behavior is that of a color glass condensate. We also show that Gubser flow can be smoothly glued to the vacuum outside the future Minkowski wedge generically given that the energy density vanishes faster than any power when extrapolated to early proper time or to large distances from the central axis. We find that at intermediate times the ratio of both the transverse and longitudinal pressures to the energy density converge approximately to a fixed point which is hydrodynamic only for large initial energy densities. We argue that our results suggest that the Gubser flow is better applied to collective behavior in jets rather than the full medium in the phenomenology of heavy ion collisions and can reveal new clues to the mechanism of confinement. The talk will be based on Mitra, Mondkar, Mukhopadhyay, Soloviev, arxiv:2408.04001/hep-th (accepted for publication in JHEP).

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Asymmetries in Stripped Envelope Supernovae

October 25 (Fri) at 14:00 - 15:15, 2024

Thomas Maunder (Ph.D. Student, Department of Astronomy, Monash University, Australia)

The explosion mechanism of supernovae is not yet fully understood. In order to better understand the inner-workings of the explosion we need to be able to test our models with observations. Current hydrodynamic simulations of stellar explosions often do not provide photometry or spectroscopy as this requires a treatment of the radiation transport of the ejecta. This project takes hydrodynamic simulations of Type Ib/c (stripped-envelope) supernovae and then performs Monte Carlo Radiative Transport simulations on the ejecta to obtain results we can compare with observations. We choose stripped-envelope supernovae because the lack of Hydrogen shell provides a more direct view into the core and the asymmetries of the explosion mechanism. Through these comparisons between models and observations we can improve our understanding of the explosion mechanism in core-collapse supernovae.

Venue: via Zoom

Event Official Language: English

The hidden language of light: Polarization signals in cuttlefish courtship

October 24 (Thu) at 16:00 - 17:00, 2024

Arata Nakayama (Postdoctoral Fellow, Atmosphere and Ocean Research Institute, The University of Tokyo)

The most conspicuous signals are generally the most attractive; this principle underlies the evolution of sexual signal. While the sexual signal design and its exceptional diversity have primarily explored on the color (wavelength) of light, various animals utilize a different property of light for signaling: polarization. In short, polarization is a third physical property of light, alongside color and intensity, and refers to the orientation of light waves' vibrations. While most vertebrate species, including humans, cannot perceive polarized light, some invertebrate species, such as crustaceans and cephalopods (e.g., octopus, squid, and cuttlefish), can detect the polarization of light and reflect polarized light from their body surfaces, suggesting that the polarization of light might function as a communication signal. In our study, by focusing on the sexually ornamented trait and the courtship behavior of specific cephalopod species, we found an polarization courtship signal, which is extremely conspicuous from the perspective of cephalopod polarization vision. Additionally, we conducted morphological observations and optical analyses of their polarization-reflective body surfaces, uncovering a novel mechanism for generating complex polarization patterns. In this gethering, I will provide a general introduction to the role of polarization as a visual cue and signal, followed by an overview of our study on the unique courtship behavior involving polarization signaling in the cuttlefish Sepia andreana.

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

Event Official Language: English

Young's convolution inequality on locally compact groups

October 18 (Fri) at 15:00 - 17:00, 2024

Takashi Satomi (Special Postdoctoral Researcher, iTHEMS)

Young's convolution inequality is one of the elementary inequalities in functional and harmonic analysis, and this inequality is related to various theories in mathematics, physics, and computer theory. In addition, it is known that Young's inequality can be generalized to any locally compact group. In this talk, we introduce the definition of locally compact groups and the statement of Young's inequality with several examples. Finally, we see the speaker's recent results about refining Young's inequality for several locally compact groups, including the special linear groups.

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

Event Official Language: English

Open Effective Field Theories for primordial cosmology

October 18 (Fri) at 13:30 - 15:00, 2024

Thomas Colas (Postdoc, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK)

Imprints of new physics on observable cosmology may require the modelling of dissipation and noise. In this talk, I will present an open effective field theory for primordial cosmology where the inflaton sector interacts with an unknown environment. The approach recovers the usual effective field theory of inflation in a certain limit and extends it to account for local dissipation and noise. Non-Gaussianities are generated that peak in the equilateral configuration for large dissipation and in the folded configurations for small dissipation. The construction provides an embedding for local dissipative models of inflation and a framework to study dissipative and stochastic effects in cosmology.

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

Event Official Language: English

Digital Twinning of Plant Internal Clocks for Robotics and Virtual Reality Enhancements in Agriculture

October 17 (Thu) at 16:00 - 17:00, 2024

Hirokazu Fukuda (Professor, Graduate School of Engineering, Osaka Metropolitan University)

Digital twinning, widely used in fields like industrial and agricultural engineering, creates digital replicas of physical systems. When applied to plant circadian clocks, these digital twins simulate physiological processes governed by circadian rhythms. This technology aids in predicting and optimizing plant growth and productivity in controlled environments, such as greenhouses and plant factories (vertical farms). By understanding key processes like photosynthesis and nutrient uptake, researchers can more effectively manage environmental factors, boosting crop yields and reducing waste. The integration of robotics and virtual reality further enhances these systems, enabling precise automation and real-time optimization. This presentation will explore these advancements, with a focus on mathematical models for controlling circadian clocks.

Venue: via Zoom

Event Official Language: English

Foliation Matter Phase and Godbillon-Vey Invariant

October 16 (Wed) at 15:00 - 17:00, 2024

Taiichi Nakanishi (Ph.D. Student, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

It has been a main topic in today's physics to classify matter phases. Especially, topologically ordered phases are attracting much attension from broad perspective. However, most of mathematical structures other than the topology are not investigated yet in physics. In this talk, we present a physical model which is strongly connected to the foliation structure of the space manifold, and its field theoretical description. In such a foliation field theory, we can see the structure is highly connected to the mathematical invariant of foliation structures called Godbillon-Vey invariant. This work would be a fiest step toward shining a light on mathematical structures used in physics. This work is based on arXiv:2408.05048 with Hiromi Ebisu, Masazumi Honda, and Soichiro Shimamori.

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

Event Official Language: English