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

Interdisciplinary Science Conference in Okinawa (ISCO 2023)

2023年2月27日(月) - 3月3日(金)

The scientific method of studying the natural world has persisted over the centuries. The key to its longevity and progression lies in sharing and building upon accumulated knowledge. Physics, which explores the origin of the universe and matter; biology, which studies living organisms, and their functions and evolution; and medicine, which explores health based on the structure and function of living organisms: all have made enormous advancements that impact all aspects of our lives. As the scientific study progresses, however, additional challenges have arisen which are increasingly difficult to solve. Many of the challenges that humanity faces are in achieving sustainable development. These include environmental changes due to climate change, food crises caused by the gap between population growth and food production, and pandemics caused by the spreading of resistant bacteria and viruses. To rise to these new challenges, it is important to reassess the issues from a broader perspective: to combine the knowledge and methods of different scientific fields and to look for new approaches that can bridge the boundaries and work across multiple fields The purpose of ISCO 2023 is to bring together leading researchers in their respective fields, explore methods for solving issues through the fusion of different fields, and form a new network of researchers. The workshop will bring together speakers from Japan and abroad in the fields of space science, particle and nuclear physics, quantum computing, life sciences, and medicine to discuss the challenges they face and the latest advancements in their respective fields. We call for presentations from fields related to those subjects mentioned above and on the sustainable development of humankind. In addition, we plan to hold a poster session to facilitate a wide range of discussions. We hope that the knowledge gained at this workshop will lead to the creation of new research fields that will not only advance basic science but will also help solve the various new challenges that humanity faces.

会場: OIST Auditorium / 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

The Electron-Ion Collider: the Ultimate Electron Microscope

2023年2月20日(月) 15:00 - 16:30

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

How does the nucleon get its mass? Certainly not from the Higgs -- the rest masses of the quarks it contains add up to only one percent of the nucleon mass. Rather the remaining 99% comes from the zero-point energy of the quarks, antiquarks and gluons localized in the nucleon. How do nuclei differ from being a simple collection of nucleons? How are the gluons, for example, distributed in nuclei? Do they stick out, or are they clumped towards the center of the nucleon? Gluons, like dark matter unseen but playing the crucial role in gluing matter together, are strongly interacting. Do such gluons form new emergent quantum states in nuclei, as in condensed matter physics? And how is the spin of the proton -- the key to NMR imaging -- put together from the spin and orbital motion of the quarks and gluons in the proton?

会場: 大河内記念ホール (メイン会場) / via Zoom

イベント公式言語: 英語

階層をつなぐ科学：宇宙から生命まで

2023年2月20日(月) 10:00 - 16:45

横倉 祐貴 (数理創造プログラム 上級研究員)
伊藤 悦子 (数理創造プログラム 上級研究員)
カトゥリン・ボシゥメン (数理創造プログラム 副プログラムディレクター)

現代科学は、それぞれの研究分野が成熟して高度化・深化するにつれて、分野全体からみると細分化しすぎてしまっているという問題点も同時に生み出している。一方で、個々の研究テーマに目を向けると、宇宙創生と素粒子理論、中性子星と原子核理論、宇宙の大規模構造と銀河・星・惑星形成、幅広いスケールにわたる乱流現象、生命と非平衡現象、などのように異なる階層構造を跨ぐ研究も進展し、物理現象を統合的に捉える努力が研究者単位で広がっている。「階層」という言葉は、理論の階層、異なる原理や視点という解釈もできるだろう。 そこで今回のTJR研究会では、関連する講師を外部から招待し、それぞれの研究分野においてどのように階層構造を連結しようと努力しているかについて焦点をおいて講演をしてもらい、研究の視野を広げて新たな視点を今後の研究に取り入れてもらうことを狙いとする。もちろん若い世代に分野横断型の研究テーマを知らしめ、インスピレーションを与えて鼓舞する目的もある。

会場: 大阪大学 豊中キャンパス 南部陽一郎ホール / via Zoom

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

String theory, N=4 SYM and Riemann hypothesis

2023年2月16日(木) 14:00 - 16:10

本多 正純 (京都大学 基礎物理学研究所 助教)

We discuss new relations among string theory, four-dimensional N=4 supersymmetric Yang-Mills theory (SYM) and the Riemann hypothesis. It is known that the Riemann hypothesis is equivalent to an inequality for the sum of divisors function σ(n). Based on previous results in literature, we focus on the fact that σ(n) appears in a problem of counting supersymmetric states in the N=4 SYM with SU(3) gauge group: the Schur limit of the superconformal index plays a role of a generating function of σ(n). Then assuming the Riemann hypothesis gives bounds on information on the 1/8-BPS states in the N=4 SYM. The AdS/CFT correspondence further connects the Riemann hypothesis to the type IIB superstring theory on AdS5×S5. In particular, the Riemann hypothesis implies a miraculous cancellation among Kaluza-Klein modes of the supergravity multiplet and D3-branes wrapping supersymmetric cycles in the string theory. We also discuss possibilities to gain new insights on the Riemann hypothesis from the physics side. This talk is based on a collaboration with Takuya Yoda (arXiv:220317091).

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

Quantum groups and cohomology theories

2023年2月15日(水) 14:00 - 16:00

Yaping Yang (Senior Lecturer, University of Melbourne, Australia)

In the first half of my talk, I will review quantum groups at roots of unity and their representation theory. In the second half, I will explain a construction of new quantum groups using cohomology theories from topology. The construction uses the so-called cohomological Hall algebra associated to a quiver and an oriented cohomology theory. In examples, we obtain the Yangian, quantum loop algebra and elliptic quantum group, when the cohomology theories are the cohomology, K-theory, and elliptic cohomology respectively.

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

京都大学大学院理学研究科 x 理化学研究所iTHEMS 共同研究成果報告会 (兼) 2022年度MACS成果報告会

2023年2月13日(月) 13:00 - 18:00

理化学研究所iTHEMSと京都大学理学研究科SACRA学際融合部門は2018年度から開始された課題「数理を基盤とした分野横断的手法による、理学における新分野の創出と諸問題の解決」で共同研究契約を締結し、この5年にわたり両機関の連携強化を図ってきました。その間、研究シンポジウムの開催、大学間を横断する連携講義の実施、客員講座の設置、MACSスタディーグループでの教育活動など、研究・教育の双方で様々な連携活動を行い成果を得ました。本成果報告会ではこの五年間の共同研究の成果を紹介し、今後のさらなる連携に向けたスタートに繋げていきたいと考えています。特にMACSスタディーグループ2022-SG5理化学研究所とMACSを繋ぐパイプライン」では、多くの学部生・大学院生が参加し、理研研究者との研究活動が活発に行われてきました。今回の成果発表会ではこのSG5の活動成果を学生の皆さんから紹介していただく予定です。

会場: 京都大学大学院理学研究科6号館南棟4階 (メイン会場) / via Zoom

イベント公式言語: 日本語

Entanglement in non-Hermitian quantum systems and non-unitary conformal field theories

2023年2月9日(木) 17:00 - 18:15

Chang Po-Yao (Assistant Professor, Department of Physics, National Tsing Hua University, Taiwan)

Time: 5pm ~ 6:15pm (JST); 9am ~ 10:15am (CET); 4pm ~ 5:15pm (Taiwan) Entanglement is a powerful tool to diagnose many-body quantum systems. One example is the critical system where the low energy property can be described by conformal field theories (CFTs), and the central charge which uniquely characterizes the CFT can be perfectly extracted from the entanglement entropy. However, the entanglement properties for non-unitary CFTs are not well understood. Moreover, the entanglement properties in many-body microscopic models which can be described by non-unitary CFTs have not been explored. In this talk, I would like to demonstrate several non-Hermitian systems which can be described by non-unitary CFTs, and show their entanglement properties can be correctly obtained by the proposed generic entanglement entropy. Field: Condensed Matter Physics Keywords: non-Hermitian systems, conformal field theory, many-body systems, entanglement entropy

会場: via Webex

イベント公式言語: 英語

Elasticities of population growth and their significance to evolutionary biology

2023年2月9日(木) 16:00 - 17:00

Stefano Giaimo (Postdoc, Department for Evolutionary Theory, Max Planck Institute for Evolutionary Biology, Germany)

The elasticity of population growth to a demographic parameter quantifies the proportional sensitivity of population growth to such parameter. In this talk, I will illustrate some cases where elasticities of population growth to demographic parameters acquire a special importance to evolutionary biology. In particular, I will discuss the relevance of these elasticities in studying the evolution of aging, their role in the computation of the generation time and their relationship to some trade-offs organisms may face as they optimise their fitness.

会場: via Zoom

イベント公式言語: 英語

Boltzmann or Bogoliubov? A Case of Gravitational Particle Production

2023年2月9日(木) 13:30 - 15:00

金田 邦雄 (東京女子大学 理学研究科 特任講師)

Despite its weakness, gravity is the primordial source of particle production in the early Universe. All the particles, including dark matter, can inevitably be created after the end of inflation through gravity. To study this production channel, two different approaches have commonly been considered, one of which is based on the Boltzmann equation, and the other is based on the Bogoliubov transformation. The former approach has widely been used in phenomenological studies of dark matter, while the latter has been developed to describe particle production in curved spacetime. I will discuss when these two approaches are equivalent and when they are not by considering the pure gravitational production of a scalar particle.

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

Fuzzy DM simulation (TBA)

2023年2月9日(木) 11:00 - 12:00

Jowett Chan (Postdoc, Physics Division, National Center for Theoretical Sciences, Taiwan)

会場: via Zoom

イベント公式言語: 英語

Thermodynamic inequalities: motivation, foundations, and applications

2023年2月7日(火) 13:30 - 15:00

Andreas Dechant (京都大学 理学系研究科 講師)

In this talk, I will introduce the topic of thermodynamic inequalities. One motivation for studying inequalities is that they can provide universal constraints on what can and cannot happen in physical systems. From a more practical point of view, they can be used to estimate physical observables even in situations where no equality is available. I will highlight a few recent examples of thermodynamic inequalities in the form of uncertainty relations and speed limits. In the main part of the talk, I will explain a general technique for deriving new inequalities, by starting from information-theoretic bounds and considering “virtual perturbations” of a physical system. I will show how this method can be used to derive and generalize the so-called “thermodynamic uncertainty relation”. An interesting application of such uncertainty relations is to estimate the dissipation in biological systems such as molecular motors. The second main topic is how to relate inequalities to equalities. When using inequalities to estimate physical quantities, it is crucial to understand the conditions under which the inequality can be tight. One way to achieve this is to “promote” the inequality into an equality via a variational principle. On the one hand, this provides conditions for obtaining a tight bound. On the other hand, variational expressions can also serve as a starting point to derive new inequalities.

会場: via Zoom

イベント公式言語: 英語

Universal Biology in Adaptation and Evolution: Dimensional Reduction and Fluctuation-Response Relationship

2023年2月2日(木) 16:00 - 17:00

金子 邦彦 (Professor, Niels Bohr Institute, University of Copenhagen, Denmark)

A macroscopic theory for adaptive changes of cells is presented, based on consistency between cellular growth and molecular replication, as well as robustness of fitted phenotypes against perturbations. Adaptive changes in high-dimensional phenotypes are shown to be restricted within a low-dimensional slow manifold, from which a macroscopic law for cellular states is derived, as is confirmed by adaptation experiments of bacteria under stress. The theory is extended to phenotypic evolution, leading to proportionality between phenotypic responses against genetic evolution and by environmental adaptation, which also explains the evolutionary fluctuation-response relationship previously uncovered. Relevance of statistical-physics and dynamical-systems approach is discussed.

会場: via Zoom

イベント公式言語: 英語

Scaling Optimal Transport for High dimensional Learning

2023年1月24日(火) 17:00 - 18:30

Gabriel Peyré (Research Director, CNRS/École Normale Supérieure, France)

iTHEMS-AIP Joint Colloquium Optimal transport (OT) has recently gained a lot of interest in machine learning. It is a natural tool to compare in a geometrically faithful way probability distributions. It finds applications in both supervised learning (using geometric loss functions) and unsupervised learning (to perform generative model fitting). OT is however plagued by the curse of dimensionality, since it might require a number of samples which grows exponentially with the dimension. In this talk, I will explain how to leverage entropic regularization methods to define computationally efficient loss functions, approximating OT with a better sample complexity. More information and references can be found on the website of our book "Computational Optimal Transport" (see related link below).

会場: via Zoom

イベント公式言語: 英語

Introduction to the Quantum Theory of Gravity via Asymptotic Safety

2023年1月24日(火) - 26日(木)

太田 信義 (Visiting Professor, Department of Physics, National Central University, Taiwan)

We give an introduction to the formulation towards the quantum theory of gravity using the functional (or exact) renormalization group, the so-called asymptotic safety. First we briefly explain the necessity of quantization of gravity and why the Einstein gravity is not sufficient for this purpose. Second, we introduce the functional renormalization group equation and explain what is the asymptotic safety program to achieve the quantum theory of gravity. This includes the notion of relevant, irrelevant and marginal operators, and it is important that there are finite number of relevant operators to make any prediction of quantum effects. This gives a nonperturbatively renormalizable theory of gravity. We then discuss various examples how the program may be applied to various theories, and summarize the current status of this approach. (Tentative schedule) [Day 1: Jan. 24, 2023] Free discussion: 9:30 - 10:30 Lecture 1: 10:30 - 12:00 Lunch: 12:00 - 13:30 Lecture 2: 13:30 - 15:00 Break: 15:00 - 15:30 Lecture 3: 15:30 - 17:00 [Day 2: Jan. 25, 2023] Free discussion: 9:30 - 10:30 Lecture 4: 10:30 - 12:00 Lunch: 12:00 - 13:30 Lecture 5: 13:30 - 15:00 Break: 15:00 - 15:30 Lecture 6: 15:30 - 17:00 [Day 3: Jan. 26, 2023] Q&A + discussion: 9:30 - 15:00

会場: 研究本館 5階 535-537号室

イベント公式言語: 英語

Physics-informed deep learning approach for modeling crustal deformation

2023年1月23日(月) 10:30 - 11:30

上田 修功 (理化学研究所 革新知能統合研究センター (AIP) 副センター長)

The movement and deformation of the Earth’s crust and upper mantle provide critical insights into the evolution of earthquake processes and future earthquake potentials. Crustal deformation can be modeled by dislocation models that represent earthquake faults in the crust as defects in a continuum medium. In this study, we propose a physics-informed deep learning approach to model crustal deformation due to earthquakes. Neural networks can represent continuous displacement fields in arbitrary geometrical structures and mechanical properties of rocks by incorporating governing equations and boundary conditions into a loss function. The polar coordinate system is introduced to accurately model the displacement discontinuity on a fault as a boundary condition. We illustrate the validity and usefulness of this approach through example problems with strike-slip faults. This approach has a potential advantage over conventional approaches in that it could be straightforwardly extended to high dimensional, anelastic, nonlinear, and inverse problems.

会場: via Zoom

イベント公式言語: 英語