セミナー

Towards EeV Neutrino Astronomy with GRAND

2023年4月18日(火) 14:00 - 15:15

クミコ・コテラ (Director of Research, Institute of Astrophysics, France)

We are living exciting times: we are now able to probe the most violent events of the Universe with diverse messengers (cosmic rays, neutrinos, photons and gravitational waves). One challenge to complete the multi-messenger picture resides in the highest energies, as no ultra-high energy neutrinos have been observed yet. This challenge could be undertaken by the GRAND (Giant Radio Array for Neutrino Detection) project, which aims at detecting ultra-high energy particles, with a colossal array of 200'000 antennas over 200'000 km2, split into ~20 sub-arrays of ~10'000 km2 deployed worldwide. In this talk, we will present preliminary designs and simulation results, plans for the ongoing, staged approach to construction, and the rich research program made possible by the proposed sensitivity and angular resolution.

会場: コモンルーム (246-248号室) / via Zoom

イベント公式言語: 英語

Why are cell populations maintained via multiple compartments?

2023年4月13日(木) 10:00 - 11:00

カルメン・モリナ パリス (Researcher, Theoretical Biology and Biophysics, Los Alamos National Laboratory, USA)

We consider the maintenance of “product” cell populations from “progenitor” cells via a sequence of one or more cell types, or compartments, where each cell’s fate is chosen stochastically. If there is only one compartment then large amplification, that is, a large ratio of product cells to progenitors comes with disadvantages. The product cell population is dominated by large families (cells descended from the same progenitor) and many generations separate, on average, product cells from progenitors. These disadvantages are avoided using suitably-constructed sequences of compartments: the amplification factor of a sequence is the product of the amplification factors of each compartment, while the average number of generations is a sum over contributions from each compartment. Passing through multiple compartments is, in fact, an efficient way to maintain a product cell population from a small flux of progenitors, avoiding excessive clonality and minimising the number of rounds of division en route. We analyse the possible descendants of one progenitor cell, families of cells that journey through the sequence of compartments. We find that the ability of product cells to perform their function may be negatively affected by the number of rounds of cell division that separates them from their progenitor, because every round of division brings with it a risk of mutation.

会場: via Zoom

イベント公式言語: 英語

An overview on the nuclear equation of state studied from ground and collective excited state properties of nuclei

2023年4月12日(水) 13:30 - 15:00

Xavier Roca-Maza (Associate Professor, Department of Physics, University of Milan, Italy)

This contribution reviews a selection of available constraints to the nuclear equation of state (EoS) around saturation density from nuclear structure calculations on ground and collective excited state properties of atomic nuclei [1]. It concentrates on predictions based on self-consistent mean-field calculations, which can be considered as an approximate realization of an exact energy density functional (EDF). Mostly, EDFs are currently derived from effective interactions commonly fitted to nuclear masses, charge radii and, in many cases, also to pseudo-data such as nuclear matter properties. Although in a model dependent way, EDFs constitute nowadays a unique tool to reliablyand consistently access bulk ground state and collective excited state properties of atomic nuclei along the nuclear chart as well as the EoS. The impact on the EoS of the new CREx [2] and PREx [3] measurments of the parity violating asymmetry (ground state observable) in 48Ca and 208Pb, respectively, will be also discussed [4,5] and compared to previously presented results on collective excitations. As the main conclusion, the isospin dependence of the nuclear EoS around saturation density and, to a lesser extent, the nuclear matter incompressibility remain to be accurately determined. Experimental and theoretical efforts in finding and measuring observables specially sensitive to the EoS properties are of paramount importance, not only for low-energy nuclear physics but also for nuclear astrophysics applications.

会場: 理化学研究所 和光キャンパス RIBF棟 2階 大会議室 (メイン会場) / via Zoom

イベント公式言語: 英語

Quantum modularity of quantum invariants and related techniques

2023年4月11日(火) 13:00 - 15:30

村上 友哉 (九州大学 数理学研究院 日本学術振興会 特別研究員 PD)

In this talk, I will present my recent work[1] and related research. In the first half of the talk, I will provide an overview of the concept of quantum modularity of quantum invariants, and briefly discuss my main result. In the second half, I will provide a more detailed explanation of my main result and the proof.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Frobenius algebras associated with the α-induction for equivariantly braided tensor categories

2023年4月10日(月) 14:00 - 16:30

及川 瑞稀 (東京大学 大学院数理科学研究科 博士課程／日本学術振興会 特別研究員 DC)

In this talk, I would like to introduce my work https://arxiv.org/abs/2303.11845. In the first half of the talk, I will give an introduction of tensor categories. In the latter half, I will explain about my construction of some tensor categories and Frobenius algebras.

会場: セミナー室 (359号室) / via Zoom

イベント公式言語: 英語

Introduction to the Renormalization group method as a powerful reduction method of dynamics

2023年4月10日(月) 10:30 - 12:00

国広 悌二 (京都大学 名誉教授)

Extracting effective slow dynamics with fewer degrees of freedom from a complex system with many degrees of freedom is of basic importance in all areas of Science. Typical examples include the derivation of the amplitude and phase dynamics from nonlinear oscillators, that of the Boltzmann equation from Hamilton dynamics, which is further reduced to fluid dynamics and so on. The purpose of this talk is to give an elementary introduction to the renormalization group (RG) method as a powerful reduction method of differential (difference) equations in terms of the notion of envelopes. Some simple examples will be worked out in this method, which include the van der Pol (Rayleigh) equation with its discrete analog and a generic system with a bifurcation. In the final part, we list up various examples to which the RG method has been successfully applied.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Organizational meeting

2023年4月6日(木) 16:00 - 17:00

カトゥリン・ボシゥメン (理化学研究所 数理創造プログラム (iTHEMS) 副プログラムディレクター)

The purpose of the organizational meetings is to discuss various topics of interest to the members of iTHEMS in the field of Biology, but also to participants of the iTHEMS BIology Seminar, irrespective of their field. The primary objective of this meeting will be to discuss recruitment of JRAs, SPDRs, and female researchers from Biology into iTHEMS. I hope we can identify the main obstacles and consider together possible solutions. As usual, any additional topic can be brought up spontaneously by participants. Anyone with thoughts about iTHEMS Biology is welcome to join us, no matter their field.

会場: via Zoom

イベント公式言語: 英語

Gauge-equivariant neural networks as preconditioners in lattice QCD

2023年4月6日(木) 13:30 - 15:00

Tilo Wettig (Professor, Universität Regensburg, Germany)

We demonstrate that a state-of-the-art multi-grid preconditioner can be learned efficiently by gauge-equivariant neural networks. We show that the models require minimal re-training on different gauge configurations of the same gauge ensemble and to a large extent remain efficient under modest modifications of ensemble parameters. We also demonstrate that important paradigms such as communication avoidance are straightforward to implement in this framework.

会場: コモンルーム (246-248号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Asymmetric enzyme kinetics of F1-ATPase resulted from asymmetric allosterism

2023年3月30日(木) 16:00 - 17:00

中山 洋平 (東北大学 大学院工学研究科 応用物理学専攻 助教)

Bio-molecular machines play various roles in cells where thermal fluctuation is dominant. Since artificial molecular machines are far behind bio-molecular machines for the present, we should begin with understanding how bio-molecular machines are designed to play their roles. We examine the motion of a bio-molecular machine, F1-ATPase, in single molecule experiments. In particular, we focus on the operation of F1-ATPase as ATP synthase in addition to as molecular motor. In this seminar, I talk about the enzyme kinetics, dependence of reaction rate on substrate concentration, of F1-ATPase in ATP synthesis. The experimental result shows that the enzyme kinetics of F1-ATPase in ATP synthesis exhibits weaker dependence on substrate concentration than the ordinary Michaelis-Menten kinetics, whereas that in ATP hydrolysis follows Michaelis-Menten kinetics. Therefore, the enzyme kinetics of F1-ATPase turned out to be asymmetric between ATP synthesis and hydrolysis. We analyzed this asymmetry based on a potential switching model, totally asymmetric allosteric model, whose characteristic is asymmetry in angular dependence of binding rates of substrates. It was shown that the totally asymmetric allosteric model may reproduce the experimental results, where the asymmetry of binding rates is essential. We also discuss physiological roles that the asymmetry of enzyme kinetics may play.

会場: via Zoom

イベント公式言語: 英語

Warming reduces the density-dependent divergence in emergence time for two competing parasitoid species

2023年3月23日(木) 16:00 - 17:00

津田 みどり (九州大学 大学院農学研究院 資源生物科学部門 農業生物資源学 准教授)

Climate change is expected to directly affect ectothermic species through their sensitivity to temperature, with cascading effects on populations and communities. Here we experimentally tested predictions from two non-exclusive hypotheses concerning the impacts of elevated temperature (+2°C) on interactions between a single host species (the azuki bean beetle) and two species of parasitoid wasps. We hypothesized that increasing temperature shortens the time that the host is vulnerable to parasitoid attack. This change in available resource should heighten intra- and interspecific competition among parasitoids, which could induce divergence in emergence times. We found that intraspecific competition of both parasitoid species was more intense than interspecific competition irrespective of temperature. The difference (d) in the emergence times of the two parasitoid species increased with the density of each parasitoid but decreased at the elevated temperature. Both parasitoids emerged sooner at the elevated temperature and experienced a reduction in body size. Thus, high levels of intraspecific competition (along with the consequent reduction in body size) may have attenuated the intensity of interspecific competition at the elevated temperature despite a reduction in the differentiation of emergence times.

会場: via Zoom

イベント公式言語: 英語

Lab-Theory Standing Talks #1

2023年3月16日(木) 13:00 - 13:30

大岡 英史 (理化学研究所 環境資源科学研究センター (CSRS) 生体機能触媒研究チーム 研究員)

会場: 研究本館 3階 共有スペース

イベント公式言語: 英語

Towards S-matrix theory of unstable particles

2023年3月15日(水) 13:30 - 15:00

青木 勝輝 (京都大学 基礎物理学研究所 基研特任助教)

The S-matrix is one of the central objects in quantum field theory and gains renewed interest recently to understand the possible structures of low-energy effective field theories and quantum gravity. However, most of the particles have finite decay widths and thus do not appear in asymptotic states. Therefore, the standard S-matrix arguments may not be directly applied to scatterings of such unstable particles and we need to formulate “the S-matrix theory of unstable particles” to properly understand the availability of the S-matrix arguments in realistic systems. In this talk, I will talk about the first steps towards this goal. In particular, I will discuss non-perturbative consequences of unitarity in a scattering amplitude of unstable particles and its analytic properties.

会場: コモンルーム 246-248号室 とZoomのハイブリッド開催

イベント公式言語: 英語

Neutrinos from the big bang: probing cosmic gravitational inhomogeneities & magnetic fields in the early universe

2023年3月13日(月) 13:30 - 15:00

ゴードン・ベイム (Professor Emeritus, University of Illinois, USA)

Primordial neutrinos from the Big Bang are about 100 times more prevalent than solar neutrinos, and at least two-thirds of them are now non-relativistic. These relic neutrinos, which have never been detected, decoupled in the early universe predominantly in helicity eigenstates. As I will discuss, their subsequent propagation through gravitational inhomogeneities and even background gravitational radiation, as well as cosmic and galactic magnetic fields partially flips their helicities, and can produce noticeable effects in their eventual detection. I will briefly mention future detection of relic neutrinos.

会場: コモンルーム (246-248号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Cosmic magnetism and its effects on the observed properties of ultra high-energy cosmic rays

2023年3月10日(金) 14:00 - 15:00

Ellis Owen (大阪大学 大学院理学研究科 宇宙地球科学専攻 宇宙進化グループ JSPS特別研究員)

Ultra high-energy (UHE) cosmic rays (CRs) from distant sources interact with intergalactic radiation fields, leading to their spallation and attenuation through photo-hadronic processes. Their deflection and diffusion in large scale intergalactic magnetic fields (IGMFs), in particular those associated with Mpc-scale structures, alter the cumulative cooling and interactions of a CR ensemble to modify their spectral shape and composition observed on Earth. In this talk, I will demonstrate the extent to which IGMFs can affect observed UHE CRs, and show that source population models are degenerate with IGMF properties. Interpretation of observations, including the endorsement or rejection of any particular UHE CR source classes, needs careful consideration of the structural properties and evolution of IGMFs. Future observations providing tighter constraints on IGMF properties will significantly improve confidence in assessing UHE CR sources and their intrinsic CR production properties.

会場: via Zoom / コモンルーム (246-248号室)

イベント公式言語: 英語

Feynman’s proof of integrability of Calogero system from a modern point of view

2023年3月10日(金) 10:00 - 11:30

Yehao Zhou (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任研究員)

In his last year of life Feynman was interested in integrable system, and in his study of Calogero models he came up with his own proof of the commutativity of integrals of motions of these models, which remains unpublished until it was transcribed by Polychronakos in 2018. His idea is to organize integrals of motions of a Calogero model into a generating function of differential operators which look like a correlation function in a certain free theory, then he showed that the generating function of differential operators commute for all spectral values, which leads to a proof of commutativity of integrals of motions. He commented on his proof “I learn nothing, no real clue as to why all this works, and what it means”. Recently in a joint work with Davide Gaiotto and Miroslav Rapcek we identify Feynman’s generating function as the correlation function of Miura operators in a W-algebra of type A, and in the rational and trigonometric cases we show that they equal to certain elements in the Dunkl representation of corresponding spherical Cherednik algebras in type A, which make the commutativity self-evident. This progress is a byproduct of a project in the study of M2-M5 brane junction in the M-theory.

会場: コモンルーム (246-248号室) / via Zoom

イベント公式言語: 英語

Reproductive interference can affect trait diversity of closely related animal species

2023年3月9日(木) 16:00 - 17:00

森田 慶一 (総合研究大学院大学 先導科学研究科 生命共生体進化学専攻 博士課程)

Previous theoretical studies have considered that evolution driven by resource competition is important for the creation and maintenance of biodiversity. Recently, reproductive interference caused by misrecognition of sexual traits such as calling between closely related species has been increasingly important for the creation and maintenance of diversity, but the impact of reproductive interference on trait diversity between closely related species remains unresolved. In this study, we combined population dynamics model with reproductive interference in two closely related species with an evolutionary model of traits related to reproduction to examine the impact of reproductive interference on the evolutionary consequences of reproductive traits in the two closely related species. The model assumed a trade-off in which reproductive interference weakens as reproductive traits diverge between the two species, but predation pressure increases as the reproductive traits diverge from their optimum traits in their habitat. For simplicity, we assumed that only one species evolves. Our model analysis revealed that convergence and divergence of traits of two closely related species occurs depending on initial trait divergence. Also, under the parameter condition where trait convergence occurs, large mutation makes trait divergence possible. Our model will provide a new framework for understanding evolutionary dynamics in ecological communities containing closely related species.

会場: via Zoom

イベント公式言語: 英語

Topological Kondo superconductors

2023年3月2日(木) 17:00 - 18:15

Yung-Yeh Chang (Postdoctoral Researcher, National Center for Theoretical Sciences & National Chiao Tung University, Taiwan)

Spin-triplet p-wave superconductors are promising candidates for topological superconductors. They have been proposed in various heterostructures where a material with strong spin-orbit interaction is coupled to a conventional s-wave superconductor by proximity effect. However, topological superconductors existing in nature and driven purely by strong electron correlations are yet to be studied. Here we propose a realization of such a system in a class of Kondo lattice materials in the absence of proximity effect. Therein, the odd-parity Kondo hybridization mediates ferromagnetic spin-spin coupling and leads to spin-triplet resonant-valence-bond (t-RVB) pairing between local moments. Spin-triplet p±p’ wave topological superconductivity is reached when Kondo effect co-exists with t-RVB [1]. We identify the topological nature by the non-trivial topological invariant and the Majorana zero modes at edges. Our results on the superconducting transition temperature, Kondo coherent scale, and onset temperature of Kondo hybridization not only qualitatively but also quantitatively agree with the observations for UTe2, a U-based ferromagnetic heavy-electron superconductor. *This work is supported by the National Science and Technology Council, Taiwan. Field: condensed matter physics Keywords: strongly correlated systems, topological superconductor, Kondo effect, resonant valence bond, heavy-fermion compounds

会場: via Webex

イベント公式言語: 英語

How to sit Maxwell and Higgs on the boundary of AdS

2023年2月28日(火) 13:30 - 15:00

Matteo Baggioli (Associate Professor, School of Physics and Astronomy, Shanghai Jiao Tong University, China)

Within the holographic correspondence, boundary conditions play a fundamental role in determining the nature of the dual field theory. In this talk, I will show how to exploit mixed boundary conditions to obtain dynamical electromagnetism in the boundary theory. This is necessary to apply AdS-CFT to many real-world applications, e.g., magnetohydrodynamics, plasma physics, superconductors, etc. where dynamical gauge fields and Coulomb interactions are fundamental. As a proof of concept, I will show two emblematic cases. First, I will prove that the results from the 4-dimensional Einstein-Maxwell bulk theory with these deformed boundary conditions are in perfect agreement with relativistic magneto-hydrodynamics in 2+1 dimensions. Second, I will discuss the collective excitations of a bona-fide holographic superconductor and prove the existence of the Anderson-Higgs mechanism therein.

会場: 中央大学後楽園キャンパス 6号館 6209教室 (メイン会場) / via Zoom

イベント公式言語: 英語

Algebra of symmetry in BF-like models in 3d and 4d

2023年2月22日(水) 14:00 - 15:30

Christophe Goeller (Humboldt Fellow, Ludwig-Maximilians-Universität München, Germany)

In this talk, I will discuss the construction of the boundary symmetry algebra for BF-like theories in 3D and 4D. In the 3D case, the theory corresponds to (an extension of) 3D gravity allowing for a source of curvature and torsion. I will show how the study of the current algebra and its associated Sugawara construction allows for two notions of quadratic charges (the usual diffeomorphism and its "dual") independently of boundary conditions. I will discuss their resulting algebra and its relation with the usual construction of the asymptotic boundary algebra. In the 4D case, a similar yet fundamentally different construction is possible, similarly resulting in multiple quadratic charges. I will discuss their constructions and their possible relations to 4D gravity.

会場: コモンルーム 246-248号室 とZoomのハイブリッド開催

イベント公式言語: 英語

Coherent sheaves, quivers, and quantum groups

2023年2月17日(金) 14:00 - 16:00

Gufang Zhao (Senior Lecturer, University of Melbourne, Australia)

This talk aims to illustrate symmetries in geometry. The first half surveys a few examples of parametrizing coherent sheaves on a variety and how quantum groups control the symmetry of parametrization space. The second half aims to illustrate some special cases when the variety is a local toric 3-Calabi-Yau.

会場: コモンルーム 246-248号室 とZoomのハイブリッド開催

イベント公式言語: 英語