2d Cardy-Rabinovici model with the modified Villain lattice formulation

2025年5月9日(金) 14:00 - 15:00

片山 颯 (京都大学 基礎物理学研究所 博士課程)

One of the most famous scenarios of the quark confinement problem is the dual superconductor picture. In this picture, the quark confinement is induced by monopole condensation, but in the theory with a θ term, we expect that not only monopole but also dyon condensation is induced, as suggested by Cardy and Rabinovici through their intuitive arguments. In this study, the Witten effect of the theory of two-dimensional compact bosons with the θ term is examined using a modified Villain-type lattice theory that can treat the θ term and dion in a rigorous manner. In addition, we construct the 2d Cardy-Rabinovici model and analyze the phase diagram through the scaling dimension argument and the anomaly matching constraint.

会場: 研究本館 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

The role of the visual information of fish schooling via selective decision-making

2025年5月8日(木) 16:00 - 17:00

伊藤 将 (東北大学 大学院理学研究科 物理学専攻 博士課程)

Visual cues play crucial roles in the collective motion of animals, birds, fish, and insects. Recently, experiments have revealed that organisms such as fish selectively utilize a portion, rather than the entirety, of visual information. This method of the visual interaction avoids heavy load for small brain of the organisms. However, the previous models using visual interaction implicitly assume that an agent interacts with all visible neighbors. Therefore, we study the effect of the selective decision-making on the collective motion via the agent-based model and the coarse grained continuous model. In the former study, we have constructed a visual model which takes into account the motion of visual attention of agents induced by the visual stimuli, and our model can simultaneously show the spontaneous appearance of various collective patterns and the bifurcation process of the tracking of a neighbor. The later study, the agents corresponds to the density field by the coarse graining, and the visual occlusion is treated in a self-consistent manner via a coarse-grained density field, which renders the interaction effectively pairwise. The model exhibits a discontinuous transition as in the conventional models by the local collision, and but the discontinuity is weakened by the non-locality of visual interaction. Our studies clarify the comprehensive coincidence with experimental results via selective decision-making and the essential role of non-locality in the visual interactions.

会場: via Zoom

イベント公式言語: 英語

3rd Mathematical Application Research Team Meeting

2025年5月2日(金) 13:30 - 15:00

アントワーヌ・ディエズ (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 数学応用研究チーム 研究員)

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Supernova axion emissivity with Δ(1232) resonance in heavy baryon chiral perturbation theory

2025年5月1日(木) 16:00 - 17:30

Shu-Yu Ho (Postdoctoral Researcher, Institute of Physics, Academia Sinica, Taiwan)

Abstract: In this talk, we evaluate the energy loss rate of supernovae induced by the axion emission process π− + p → n + a with the Δ(1232) resonance in the heavy baryon chiral perturbation theory for the first time. Given the axion-nucleon-∆ interactions, we include the previously ignored Δ-mediated graphs to the π− + p → n + a process. In particular, the Δ_0-mediated diagram can give a resonance contribution to the supernova axion emission rate when the center-of-mass energy of the pion and proton approaches the Δ(1232) mass. With these new contributions, we find that for the typical supernova temperatures, compared with the earlier work with the axion-nucleon (and axion-pion-nucleon contact) interactions, the supernova axion emissivity can be enhanced by a factor of ∼ 4(2) in the Kim-Shifman-Vainshtein-Zakharov model and up to a factor of ∼ 5(2) in the Dine-Fischler-Srednicki-Zhitnitsky model with small tanβ values. Remarkably, we notice that the Δ(1232) resonance gives a destructive contribution to the supernova axion emission rate at high supernova temperatures, which is a nontrivial result in this study.

会場: 研究本館 3階 345−347号室 (メイン会場) / via Zoom

イベント公式言語: 英語

ComSHeL Launch Meeting

2025年5月1日(木) 14:00 - 15:00

This is the very first meeting of the new Computationally-drive Solutions for Healthier Lives (ComSHeL) Study Group. The study group brings together members from iTHEMS' Fundamental Division together with the ECL Mathematical Genomics Unit and Teams from iTHEMS Applied Math Division (Medical Science Data-driven Math Team and Medical Science Deep Learning Team). The goal of this first meeting will be to discuss and decide on the format for this monthly study group, and to get to know each other (each member introducing their research briefly). I hope you can take the time to join us.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

第28回 MACSコロキウム・2025年度MACS学生説明会

2025年4月25日(金) 14:45 - 18:30

鍛冶 静雄 (九州大学 マス・フォア・インダストリ研究所 教授 / 京都大学 大学院理学研究科 附属サイエンス連携探索センター (SACRA) 教授)

14:45-15:00 ティータイムディスカッション 15:00-16:00 鍛冶 静雄（九州大学マス・フォア・インダストリ研究所 教授／京都大学理学研究科附属サイエンス連携探索センター 教授）「折り紙にひそむ数学：カライドサイクルの幾何学」 16:15-17:20 2024年度MACS学生説明会 17:30-18:30 継続討論会

会場: 京都大学 理学研究科セミナーハウス（建物配置図（北部構内）【10】の建物）

イベント公式言語: 日本語

Insights on Issues in the Cold Dark Matter Hypothesis

2025年4月25日(金) 14:00 - 15:15

Yuka Kaneda (筑波大学 数理物質科学研究群 物理学学位プログラム 博士課程)

Dark matter accounts for 85% of the matter component of our universe, but its true nature is still unclear. The Lambda-Cold Dark Matter (CDM) model, which thought to be the standard model, reproduces well the statistical properties of the large-scale structure of our universe. However, at the scale of galaxies and dwarf galaxies, serious discrepancies between the predictions of the CDM model and observations have been pointed out. In this study, we tackle on the “cusp-core problem” and the “missing satellite problem,” which are typical examples of such discrepancies, using N-body simulations. In the talk, the physical trigger of cusp-to-core transition and the novel method to find missed satellites are presented.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Asymptotic Waves in Stars

2025年4月23日(水) 14:00 - 15:30

Jim Fuller (Professor, Division of Physics, Mathematics, and Astronomy (TAPIR), California Institute of Technology (Caltech), USA)

Waves propagating through stars often have very short wavelengths in the radial direction, enabling WKB approximations that facilitate understanding. The main types of waves that propagate in stars are acoustic waves (restored by pressure forces) and gravity waves (restored by buoyancy forces). I will also discuss how the properties of these waves are changed by rotation (adding Coriolis and centrifugal forces) and magnetic fields (adding Lorentz forces). Finally, I will discuss how these waves carry energy and angular momentum through stars, and discuss some potential consequences for stellar evolution.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

From Quarks to Neutron Stars: Insights from kHz gravitational waves

2025年4月23日(水) - 24日(木)

Astronomical observations of binary neutron star mergers and supernovae provide unique opportunities to explore physics spanning from quarks to neutron stars. The groundbreaking multi-messenger observation of GW170817, combining electromagnetic signals and gravitational waves, vividly demonstrated this potential. Furthermore, if a core-collapse supernova were to occur in our galaxy, it would likely become the first event where electromagnetic signals, neutrinos, and gravitational waves are detected together. The interior of neutron stars is not yet well understood due to their extreme density, where exotic states of matter may emerge. Gravitational waves, particularly in the kilohertz band, play a crucial role in extracting information about such ultra-high densities. In recent years, several concepts for kilohertz-band gravitational wave detectors, such as Australia's NEMO, have been proposed to advance multi-messenger studies of high density astrophysical objects. KAGRA in Japan is also exploring upgrades aimed at enhancing high-frequency sensitivity, which could significantly improve sky localization accuracy and enable the detection of post-merger signals. This workshop aims to explore the transformative potential of high-frequency gravitational wave observations for multi-messenger astrophysics, with a focus on their implications for nuclear and neutron star physics. The workshop aims to spark dynamic discussions and cultivate new collaborations among participants through invited talks by leading experts and engaging poster presentations.

会場: via Zoom

イベント公式言語: 英語

On IR/UV divergence of inflationary decoherence

2025年4月22日(火) 14:00 - 15:30

佐野 文哉 (東京科学大学 博士課程)

Supported by observational evidence indicating that cosmological scalar perturbations were nearly Gaussian at the beginning of the universe, it is anticipated that the origin of these perturbations is quantum fluctuations. Consequently, cosmic inflation provides a valuable laboratory for testing the quantum nature with/of gravity. Evaluation of the quantumness of the primordial perturbations is an inevitable step for the purpose. However, quantum states of the perturbations are suffered from IR/UV divergence, resulting in fully classical states. In this presentation, I will first review the evaluation of the quantum coherence in de Sitter spacetime as a measure of quantumness, and then show how to regularize the divergence.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

iTHEMS × academist オンラインイベント「数理で読み解く科学の世界 2025」

2025年4月19日(土) 10:00 - 15:30

金久保 優花 (理化学研究所 数理創造研究センター (iTHEMS) 国内外連携・人材育成部門 理研バークレーセンター 特別研究員)
北村 侃 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 基礎科学特別研究員)
シュパイデル 玲雄 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 数理遺伝学理研ECL研究ユニット 理研ECL研究ユニットリーダー)
横倉 祐貴 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 上級研究員)

「数理で読み解く科学の世界」は、2020年より毎年4月に開催しているオンラインイベントです。主催のiTHEMSは、「数学」を共通言語として、物理、生物、宇宙などさまざまな科学分野の横断的な研究をしており、イベントでは、iTHEMS所属の若手研究者4名が最先端の研究について中学生や高校生にもわかるように30分程度の講演を行います。また、一般参加者からの質問やコメントを受け付ける時間も設けています。 詳細、参加お申し込みは、関連リンクをご覧ください。 日時：2025年4月19日（土）10:00〜15:30（開場 9:45） 場所：Web会議サービス「Zoom」（申込者に事前に招待URLをお伝えいたします） 参加費：無料 対象者：中学生・高校生、社会人（どなたでもご参加いただけます） 主催：iTHEMS 共催（企画・運営・宣伝）：アカデミスト株式会社 特別協力：NPO法人 数理の翼 タイムスケジュール： 10:00～　開始の挨拶・イベント概要説明 10:15～　講演「太陽より熱いスープ - クォーク・グルーオン・プラズマのレシピ」金久保 優花 博士 11:15～　講演「数、形、対称性」北村 侃 博士 12:10～　昼休み企画　「数学者と物理学者が語る！これからの数理の未来」 13:05～　講演「数理と遺伝情報で紐解く人類史」シュパイデル 玲雄 博士 14:05～　講演「ブラックホールは情報の玉手箱？」横倉 祐貴 博士 15:00〜　アフタートーク 15:30　　終了予定

会場: via Zoom

イベント公式言語: 日本語

Artificial Intelligence and Neuroscience

2025年4月11日(金) 14:00 - 15:30

近添 淳一 (広島大学 脳・こころ・感性科学研究センター 教授)

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.

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

iTHEMS Biology Study Group April Launch Meeting (Part 2)

2025年4月10日(木) 13:00 - 14:00

Let's launch our Biology Study Group activities for the new year (Part 2 of 2). This meeting will be used to (1) say welcome to new member (SPDR Kenji Okubo, and Postdoc Lucas Sort); (2) discuss Biology seminar management in light of the new iTHEMS Centre; and (3) catch up on each other's current research. Since this will probably take us 2h, this will be Part 2 of 2 (Part 1 was on 4/3). On 4/10 (Part 2) we will get a 15 min introduction talk by Postdoc Lucas Sort. This meeting is open to all RIKEN and guests. You do not need to be a member of the iTHEMS Biology Study Group.

会場: via Zoom / 研究本館 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

A Strategy for Proving the Strong Eigenstate Thermalization Hypothesis: Chaotic Systems and Holography

2025年4月3日(木) 16:00 - 17:00

川本 大志 (京都大学 基礎物理学研究所 博士課程／日本学術振興会 特別研究員 DC)

The strong eigenstate thermalization hypothesis (ETH) provides a sufficient condition for thermalization and equilibration. Although it is expected to hold in a wide class of highly chaotic theories, there are only a few analytic examples demonstrating the strong ETH in special cases, often through methods related to integrability. In this talk, I will explore sufficient conditions for the strong ETH that may apply to a broad range of chaotic theories. These conditions are expressed as inequalities involving the long-time averages of real-time thermal correlators. Specifically, I will discuss bottom-up holographic models that satisfy these conditions under certain assumptions, which are expected to hold in such models. This talk is based on the preprint 2411.09746 [hep-th].

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Gauge subtleties and the finiteness of loop corrections beyond slow roll

2025年4月3日(木) 14:00 - 15:30

Danilo Artigas (京都大学 大学院理学研究科 物理学・宇宙物理学専攻 物理学第二教室 学振特別研究員PD)

The early universe undergoes a phase of exponential expansion called inflation, under which quantum fluctuations are amplified and later seed cosmological structures. A long-standing question is whether interactions of these quantum fields may significantly affect the n-point statistics of cosmological observables. These corrections are known as loop corrections. Recently, Kristiano and Yokoyama claimed that, in scenarios beyond slow-roll inflation, the one-loop correction of super-Hubble fluctuations could become non-negligible and violate cosmological-perturbation theory. This result is highly debated, and in this talk we will use a non-linear approach known as delta N formalism to evaluate these loop corrections. We find the existence of loop corrections for modes close to the Hubble scale, however, these corrections are quickly suppressed for long-wavelength modes. We also show how the result of Kristiano and Yokoyama may arise when truncating the perturbative expansion, and how this result depends on the chosen gauge.

会場: セミナー室 (359号室)

イベント公式言語: 英語

iTHEMS Biology Study Group April Launch Meeting (Part 1)

2025年4月3日(木) 14:00 - 15:00

Let's launch our Biology Study Group activities for the new year (Part 1 of 2). This meeting will be used to (1) say welcome to new member (SPDR Kenji Okubo, and Postdoc Lucas Sort); (2) discuss Biology seminar management in light of the new iTHEMS Centre; and (3) catch up on each other's current research. Since this will probably take us 2h, this will be Part 1 of 2 (Part 2 on 4/10). On 4/3 (Part 1) we will get a 15 min introduction talk by SPDR Kenji Okubo. This meeting is open to all RIKEN and guests. You do not need to be a member of the iTHEMS Biology Study Group.

会場: via Zoom / 研究本館 4階 共有スペース

イベント公式言語: 英語

Omega Meson from Lattice QCD

2025年4月2日(水) 15:00 - 16:00

Haobo Yan (Ph.D. Student, School of Physics, Peking University, China)

The three-body problem, renowned for its unsolvable nature in celestial mechanics and homonymous science fiction, is not only solvable in the quantum realm regarding spectra but also offers profound insights into QCD. In this talk, I will present the first-ever lattice calculation of the resonance parameters for the lightest hadron decaying into three particles, the -meson. By mapping finite-volume energy levels to infinite-volume scattering amplitude, a pole position trajectory is obtained that, when extrapolated to the physical point, shows good agreement with the experiment.

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