非可換ゲージ理論の量子シミュレーション

2026年4月7日(火) 18:00 - 19:30

花田 政範 (Reader, School of Mathematical Sciences, Queen Mary University of London, UK)

Kogut-Susskingハミルトニアンを用いればゲージ理論の量子シミュレーションができ、高エネルギー物理学の様々な問題を解けるはずであると言われて久しいのですが、実際にどのような研究がなされたのかを調べてみると、非可換ゲージ理論に関する論文が極端に少ないことに気が付きます。これは、Kogut-Susskingハミルトニアンは非可換ゲージ理論の場合にはとても複雑で、量子回路を構成する（ = プログラムをコンパイルする）以前に、そもそもハミルトニアンをqubitの言葉に書き直すための一般論すら存在しないからです。具体的には、無限次元のヒルベルト空間を正則化して有限自由度で近似する際に、SU(N)のような非自明な群多様体をどう扱えば良いのかが分かっていません。 この問題は、Kogut-Susskingハミルトニアンではなくてもっと筋の良いハミルトニアンを用いることで容易に回避できます。具体的には、Kaplan, Katz, Unsalによって構成されたorbifold lattice Hamiltonianを用いるのが便利です。Orbifold lattice Hamiltonianはゲージ場とスカラー場が相互作用する系を記述しますが、スカラー場は連続極限には寄与しません。（大きな質量を手で与えてUVの物理にすら寄与しなくすることも可能です。）しかし、ゲージ場とスカラー場をまとめて複素行列として記述するので、リンク変数がSU(N)ではなく\mathbb{C}^{N^2} = \mathbb{R}^{2N^2}に値をとります。たったこれだけの違いで、無限次元のヒルベルト空間の正則化が劇的に簡単になり、任意のSU(N)について効率的な量子回路を解析的に書き下すことが可能になります。 本講義では、量子シミュレーションの基礎から出発し、QCDを含む一般的な非可換ゲージ理論の時間発展を記述する量子回路を構成してシミュレーションコストを見積もるところまで解説したいと思います。 (3/24, 3/31, 4/7 の3回シリーズ)

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: 日本語

Quantum Computation SG seminar 2026

2026年4月7日(火) 15:00 - 17:00

Self-introductions (name + research interests) and discussion about study group activities in FY2026.

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

Physics-based eruption forecasting at Kīlauea volcano using an Ensemble Kalman Filter

2026年4月7日(火) 13:00 - 14:30

Kyle R. Anderson (Research Geophysicist, California Volcano Observatory, U.S. Geological Survey (USGS), USA)

Today, most forecasts of volcanic eruptions are based on expert opinion, making them fundamentally subjective. Such forecasts have often proven successful but have clear limitations. Novel quantitative forecasting techniques have shown promise in experimental settings (hindcasting) but face numerous operational challenges and most have rarely if ever been applied to real-world eruptions (forecasting). In this talk I will discuss efforts to forecast a remarkable ongoing series of more than 40 high lava fountain eruptions at Kīlauea volcano, Hawaii, using a simple physics-based model in an Ensemble Kalman Filter (EnKF) data assimilation algorithm. Using this method, which is believed to be the first implementation of a physics-based EnKF eruption forecast, the times of Kīlauea’s lava fountain eruptions can be forecast days to weeks in advance. The method assimilates geodetic data to constrain the evolving state of the system, provides insight into the eruption mechanism and rate of magma supply to the volcano, and produces fully probabilistic forecasts. These forecasts are combined with other information, including forecasts based on machine learning algorithms, to derive forecast windows, which are disseminated to the public and to partner agencies for hazards mitigation activities. In this way, novel eruption forecasting tools are continually developed which serve an important public need while also improving understanding of the volcanic system.

会場: Hybrid Format (RIKEN R-CCS room C107 and Zoom)

イベント公式言語: 英語

A Hybrid Pseudo-spectral–PINN Approach to Black Hole Quasinormal Modes

2026年4月3日(金) 14:00 - 15:15

Alexandre M. Pombo (PD, Institute of Physics of the Czech Academy of Sciences, Czechia)

Gravitational-wave detections by the LIGO-Virgo-KAGRA network have turned compact-object mergers into precision probes of strong gravity. The post-merger ringdown is particularly incisive: it is governed by quasinormal modes (QNMs), the damped oscillations that encode the remnant's structure and provide a fingerprint of the final object. While current detectors constrain the dominant mode, next-generation observatories will resolve multiple modes with high precision, placing stringent demands on the accuracy of theoretical predictions. Computing QNMs for rotating black holes is, however, a non-trivial task, as it requires solving highly coupled, complex-valued perturbation equations where standard methods struggle. In this talk, I present SpectralPINN, a hybrid solver combining Pseudo-spectral methods with Physics-Informed Neural Networks, validated at 10⁻⁵ relative accuracy. I will present results for Kerr and Kerr-Newman black holes, demonstrating the method's robustness and accuracy across parameter space, and discuss its potential for extension to more exotic compact objects relevant to next-generation detector science.

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

Tensor networks for QCD in the strong-coupling expansion

2026年4月2日(木) 15:30 - 17:00

Tilo Wettig (Professor, Universität Regensburg, Germany)

We present the order-separated Grassmann higher-order tensor renormalization group (OS-GHOTRG) method for QCD with staggered quarks in the strong-coupling expansion. Themethod allows us to determine the expansion coefficients of the partition function, from which we can obtain the strong-coupling expansions of thermodynamical observables. We use the method in two dimensions to compute the free energy, the particle-number density, and the chiral condensate as a function of the chemical potential up to third order in the inverse coupling 𝛽. Although the expansion itself is only a good approximation to the full theory at small 𝛽, we show that in the vicinity of the phase transition the range of applicability can be greatly extended by fits to judiciously chosen transition functions. These fits also yield a valuable expansion of the critical chemical potential in 𝛽. https://www.uni-regensburg.de/physics/hep/people/professors/wettig/index.html

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

A mathematical promenade in microscopic locomotion

2026年4月2日(木) 13:00 - 14:00

Clément Moreau (CNRS Researcher, CNRS, France)

The microscopic world offers a fascinating diversity of locomotion strategies, relying primarily on the use of flagella and cilia. These slender structures, capable of complex periodic deformations, serve as a major source of inspiration for medical microrobotics. At this scale, fluid dynamics is governed by the predominance of viscosity over inertia. This low-Reynolds number regime imposes strict physical constraints, summarized by the famous « scallop theorem »: a reciprocal deformation cannot produce any net displacement. Mathematically, this is framed by the Stokes connection, which links changes in body shape to net movement in space. This presentation proposes a journey through the modeling principles of microscopic swimmers. We will see how to derive analytical solutions to the locomotion problem by simplifying degrees of freedom or by assuming small deformation amplitudes. I will then present the perspective of control theory to address the « controllability » property, i.e. the ability of a locomotor to reach any target position and shape. Finally, I will question a classic hypothesis in the field: the inextensibility of flagella. Although the literature often assumes these structures are rigid in the longitudinal direction, certain micro-organisms and artificial robots exhibit significant compression variations. I will present recent results, based on classical modeling tools, exploring the influence of compression-curvature coupling on locomotion efficiency at low Reynolds numbers.

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

非可換ゲージ理論の量子シミュレーション

2026年3月31日(火) 18:00 - 19:00

花田 政範 (Reader, School of Mathematical Sciences, Queen Mary University of London, UK)

Kogut-Susskingハミルトニアンを用いればゲージ理論の量子シミュレーションができ、高エネルギー物理学の様々な問題を解けるはずであると言われて久しいのですが、実際にどのような研究がなされたのかを調べてみると、非可換ゲージ理論に関する論文が極端に少ないことに気が付きます。これは、Kogut-Susskingハミルトニアンは非可換ゲージ理論の場合にはとても複雑で、量子回路を構成する（ = プログラムをコンパイルする）以前に、そもそもハミルトニアンをqubitの言葉に書き直すための一般論すら存在しないからです。具体的には、無限次元のヒルベルト空間を正則化して有限自由度で近似する際に、SU(N)のような非自明な群多様体をどう扱えば良いのかが分かっていません。 この問題は、Kogut-Susskingハミルトニアンではなくてもっと筋の良いハミルトニアンを用いることで容易に回避できます。具体的には、Kaplan, Katz, Unsalによって構成されたorbifold lattice Hamiltonianを用いるのが便利です。Orbifold lattice Hamiltonianはゲージ場とスカラー場が相互作用する系を記述しますが、スカラー場は連続極限には寄与しません。（大きな質量を手で与えてUVの物理にすら寄与しなくすることも可能です。）しかし、ゲージ場とスカラー場をまとめて複素行列として記述するので、リンク変数がSU(N)ではなく\mathbb{C}^{N^2} = \mathbb{R}^{2N^2}に値をとります。たったこれだけの違いで、無限次元のヒルベルト空間の正則化が劇的に簡単になり、任意のSU(N)について効率的な量子回路を解析的に書き下すことが可能になります。 本講義では、量子シミュレーションの基礎から出発し、QCDを含む一般的な非可換ゲージ理論の時間発展を記述する量子回路を構成してシミュレーションコストを見積もるところまで解説したいと思います。 (3/24, 3/31, 4/7 の3回シリーズ)

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: 日本語

Satellite Data Assimilation for Numerical Weather Prediction (NWP)

2026年3月31日(火) 14:30 - 16:00

Martin Weissman (Professor, Department of Meteorology and Geophysics, University of Vienna, Austria)

Satellite data assimilation for NWP has made tremendous progress over the past decades. Most of the assimilated observations in global NWP systems are nowadays satellite radiances from passive sensor in the infrared and microwave range. Additionally, GPS radio occultation provides information on upper-level humidity that serves as important uncalibrated anchoring information for humidity. Nevertheless, there are still significant limitations, especially in terms of lacking wind information that controls atmospheric dynamics in global NWP as well as in terms of using cloud-affected radiances in regional, convection-permitting NWP. My presentation will cover recent progress of my group in these fields.

会場: Hybrid Format (RIKEN R-CCS room C107 and Zoom)

イベント公式言語: 英語

Ecological decline and biocultural loss in Cycas revoluta landscapes of the Amami Islands

2026年3月31日(火) 13:00 - 14:00

Joshua Englehardt (Professor, Center of Archeologist Studies, El Colegio de Michoacán, Mexico)

Cycads (Cycadales) are one of the world’s most ancient plant lineages, and Cycas revoluta Thunb. (‘sotetsu,’ in Japanese) has long occupied a central place in the cultural ecologies of the Ryukyu archipelago, particularly in the Amami Islands of southern Japan. Although never domesticated, C. revoluta has held enduring alimentary, ethnoecological, and symbolic saliency within local agroecological systems, ritual landscapes, and island identities for centuries. Building on recent interdisciplinary scholarship on Japanese and Ryukyuan cycad cultures, this presentation synthesizes ethnobotanical, historical, ecological, and genetic research to detail the accelerating collapse of Amami cycad biocultural heritage. The core of this talk focuses on results from ongoing fieldwork documenting the rapid spread of cycad aulacaspis scale (Aulacaspis yasumatsui Takagi), an invasive insect that now poses an existential threat to both biological C. revoluta populations and sotetsu culture across the Amami archipelago. Drawing on systematic botanical surveys, geospatial mapping, genetic sampling, and ethnographic interviews, the presentation details how ecological decline and cultural erosion are unfolding in tandem. Population-level mortality, reproductive failure, and genetic loss are paralleled by the disappearance of knowledge, practices, and senses of place historically anchored in the islands’ cycad landscapes. By situating these findings within broader discussions of cycad use in Japan and worldwide, as well as comparative biocultural heritage studies, the presentation highlights how invasive species can rapidly destabilize long-standing human-plant relationships. The Amami case underscores the urgency of integrating biological conservation with cultural documentation at moments of irreversible ecological change, offering broader insights into island resilience, heritage loss, and the fragility of biocultural systems under accelerating environmental pressures.

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

QFT as a set of ODEs

2026年3月27日(金) 13:30 - 15:30

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

Correlation functions of local operators in Quantum Field Theory (QFT) on hyperbolic space can be fully characterized by the set of QFT data. These are the scaling dimensions of boundary operators, the boundary Operator Product Expansion (OPE) coefficients and the Boundary Operator Expansion (BOE) coefficients that characterize how each bulk operator can be expanded in terms of boundary operators. For simplicity, we focus on two dimensional QFTs and derive a universal set of first order Ordinary Differential Equations (ODEs) that encode the variation of the QFT data under an infinitesimal change of a bulk relevant coupling. In principle, our ODEs can be used to follow a renormalization group flow starting from a solvable QFT into a strongly coupled phase and to the flat space limit.

会場: via Zoom (メイン会場) / セミナー室 (359号室)

イベント公式言語: 英語

Application of a one-dimensional scheme to model diurnal water temperature fluctuations near the surface of a stratified lake

2026年3月27日(金) 10:30 - 12:00

John Craig Wells (立命館大学 理工学部 環境都市工学科 教授 / 理化学研究所 計算科学研究センター (R-CCS) データ同化研究チーム 客員主管研究員)

When simulating the atmosphere across various scales, accurately resolving the diurnal warming of sea and lake surfaces is a critical requirement. For example, regional atmospheric models must correctly simulate air-water temperature gradients to successfully capture mesoscale circulations such as sea and lake breezes. Often the SST (or Lake Surface Temperature LST) applied to the atmospheric simulator is modelled using a “slab model” of a certain thickness and thermal mass. However slab models often predict diurnal variation of SST poorly. In this talk I will discuss preliminary results from “DiuSST”, recently proposed by R. Börner et al (2025; https://doi.org/10.5194/gmd-18-1333-2025) to provide boundary conditions for diurnally varying SST to atmospheric simulators. Börner et al ’s testing and validation of DiuSST was based on an ocean cruise that measured skin surface temperature with an infrared radiometer, and water temperature at 3m depth. By contrast I cross-check DiuSST results against near-surface temperature profiles in a stratified lake, Lake Biwa, that were recorded at nearshore and offshore locations during the early summer of 2021.

会場: Hybrid Format (RIKEN R-CCS room 107 and Zoom)

イベント公式言語: 英語

Toward a Mathematical Prehistory of Homo sapiens: Data Integration and Statistical Representation in PaleoAsiaDB

2026年3月26日(木) 13:00 - 14:00

大窪 健児 (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)

This talk introduces PaleoAsiaDB, a curated database of lithic assemblages from Paleolithic Asia, and aims to initiate a discussion on its potential uses and methodological challenges. The database integrates information on tool typology, technological attributes, stratigraphy, and chronological ranges across multiple sites and periods. Archaeological assemblage data are inherently heterogeneous, combining categorical variables with hierarchical structure and, in some cases, continuous measurements. In addition, temporal information is often represented as ranges rather than precise dates, and sampling intensity varies substantially across sites. These features make it non-trivial to define consistent procedures for comparison, aggregation, and quantitative analysis. The goal of this session is to gather feedback on data representation and analysis strategies, and to clarify what types of quantitative approaches are most suitable for extracting robust patterns from archaeological assemblage data.

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

非可換ゲージ理論の量子シミュレーション

2026年3月24日(火) 18:00 - 19:00

花田 政範 (Reader, School of Mathematical Sciences, Queen Mary University of London, UK)

Kogut-Susskingハミルトニアンを用いればゲージ理論の量子シミュレーションができ、高エネルギー物理学の様々な問題を解けるはずであると言われて久しいのですが、実際にどのような研究がなされたのかを調べてみると、非可換ゲージ理論に関する論文が極端に少ないことに気が付きます。これは、Kogut-Susskingハミルトニアンは非可換ゲージ理論の場合にはとても複雑で、量子回路を構成する（ = プログラムをコンパイルする）以前に、そもそもハミルトニアンをqubitの言葉に書き直すための一般論すら存在しないからです。具体的には、無限次元のヒルベルト空間を正則化して有限自由度で近似する際に、SU(N)のような非自明な群多様体をどう扱えば良いのかが分かっていません。 この問題は、Kogut-Susskingハミルトニアンではなくてもっと筋の良いハミルトニアンを用いることで容易に回避できます。具体的には、Kaplan, Katz, Unsalによって構成されたorbifold lattice Hamiltonianを用いるのが便利です。Orbifold lattice Hamiltonianはゲージ場とスカラー場が相互作用する系を記述しますが、スカラー場は連続極限には寄与しません。（大きな質量を手で与えてUVの物理にすら寄与しなくすることも可能です。）しかし、ゲージ場とスカラー場をまとめて複素行列として記述するので、リンク変数がSU(N)ではなく\mathbb{C}^{N^2} = \mathbb{R}^{2N^2}に値をとります。たったこれだけの違いで、無限次元のヒルベルト空間の正則化が劇的に簡単になり、任意のSU(N)について効率的な量子回路を解析的に書き下すことが可能になります。 本講義では、量子シミュレーションの基礎から出発し、QCDを含む一般的な非可換ゲージ理論の時間発展を記述する量子回路を構成してシミュレーションコストを見積もるところまで解説したいと思います。 (3/24, 3/31, 4/7 の3回シリーズ)

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: 日本語

Quantum States Over Time: From Foundations To Applications

2026年3月24日(火) 15:30 - 17:00

Minjeong Song (Research Fellow, Centre for Quantum Technologies, National University of Singapore, Singapore)

In this talk, I will introduce quantum states over time (QSOT), a formalism for describing quantum systems over space-time. I will begin by reviewing how QSOT has emerged in the literature. While conventional density operator formalism has been effective across many areas of quantum information theory, QSOT was developed to meet more specialized research needs— most notably, as a key ingredient to develop a quantum version of Bayes’ theorem. I will end the first part of my talk by comparing various QSOT that have been proposed. In the second part, I will discuss the causal compatibility problem as an application of QSOT. I will focus on the temporal compatibility problem, which asks the following: from correlations in measurement outcomes alone, can two otherwise isolated parties establish whether such correlations are atemporal (i.e., temporally incompatible)? That is, can they rule out that they have been given the same system at two different times? I will first explain how characterizing measurement statistics in a causal agnostic scenario is equivalent to characterizing a specific type of QSOT, known as pseudo-density operators. I will then present our recent findings obtained by analyzing pseudo-density operators; In particular, we demonstrate that atemporality is distinct from entanglement, though they appear to be equivalent at first glance. Specifically, we show atemporality implies entanglement, but not vice versa, thus revealing that atemporality is a strictly stronger form of quantum correlations than entanglement. Nevertheless, we also find that sufficiently strong entanglement does imply atemporality.

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

Data-Driven Stratification and Prediction of Complex Diseases

2026年3月24日(火) 14:00 - 15:15

川上 英良 (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 医科学データ駆動数理チーム チームディレクター)

Many common diseases such as cancer, chronic heart failure, and diabetes exhibit substantial biological and clinical heterogeneity, which complicates diagnosis, risk assessment, and treatment decisions. In this talk, I introduce a data-driven framework for disease stratification and prediction using machine learning applied to multidimensional medical data. First, unsupervised machine learning methods are used to identify previously unrecognized disease subtypes based on clinical and biomarker data. These stratification approaches reveal hidden patient groups with distinct clinical characteristics and prognoses. To enable practical application in clinical datasets, we further develop supervised learning models that reproduce and generalize unsupervised clusters, allowing robust subtype estimation even in datasets with missing variables. Next, I present approaches for early disease detection using large-scale medical history data, focusing on combinations of comorbidities as early indicators of severe diseases. Finally, I discuss how large-scale deep learning models can be leveraged to predict disease prognosis from medical images and other high-dimensional data. These studies demonstrate how machine learning can redefine disease categories and enable earlier detection and more precise prediction in heterogeneous diseases.

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

Useless Science & Art 〜“役に立たない”科学とアートの有用性〜

2026年3月21日(土) 14:00 - 15:30

磯 暁 (理化学研究所 数理創造研究センター (iTHEMS) センター長)
初田 哲男 (理化学研究所 領域総括)
小塚 仁篤 (株式会社ADKマーケティング・ソリューションズ クリエイティブディレクター)
児玉 悠 (株式会社ADKマーケティング・ソリューションズ エクスペリエンスデザイナー)

量子ブラックホール理論に着想を得たアート作品 「Black Hole Recorder」 を入口に、科学とアートの関係を探るトークイベントを開催します。 本イベントでは、量子力学誕生から100年の歴史、最先端の量子宇宙論、そして「1500年先の未来に何を残すべきか」という問いまで、科学者とクリエイターが対話を通して考えます。 一見すると役に立たないように見える研究や表現は、長い時間をかけて未来の革新を生み出してきました。科学者の「未知への好奇心」と、アーティストの想像力がどのように重なり合い、新しい発想を生み出すのか。 作品 「Black Hole Recorder」 のコンセプトや制作背景、最新の量子ブラックホール研究について紹介するとともに、科学とアートの視点から未来の可能性を語り合います。さらに、実際に Black Hole Recorder で録音された音源を体験できるコーナー も予定しています。 科学とアートが交差する特別な対話の場に、ぜひご参加ください。

会場: 東京都現代美術館

Mouse Limb Bud Skeletal Patterning Description and Modelling

2026年3月19日(木) 13:00 - 14:00

Laura Aviñó Esteban (Ph.D. Candidate, European Molecular Biology Laboratory, Barcelona, Spain)

Understanding how complex organs reliably form during development remains a key question in biology. In this talk, I discuss how gene regulatory networks may generate skeletal patterns in the vertebrate limb, using Sox9 expression as a proxy, as it marks the earliest stages of cartilage formation. To address this, I developed new computational tools for reconstructing spatiotemporal gene expression and built models ranging from machine learning approaches to mechanistic frameworks. These analyses reveal that limb patterning cannot be explained by a single universal mechanism. Instead, different regions of the limb appear to use distinct regulatory strategies, uncovering an unexpected qualitative modularity in skeletal development. Together, these findings lead to a new hypothesis in which other systems, such as the vasculature may actively shape skeletal spacing in specific limb regions.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

Perspectives and applications of Koopman Operator Theory

2026年3月19日(木) 9:00 - 18:00

薄 良彦 (京都大学 大学院工学研究科 教授)
中尾 裕也 (東京科学大学 工学院 システム制御系 教授)
Alexandre Mauroy (Associate Professor, Mathematics, University of Namur, Belgium)
加藤 譲 (公立はこだて未来大学 システム情報科学部 複雑系知能学科 准教授)

PROGRAM: 9h45 - 10h15 Registration & Coffee 10h15 - 10h20 Opening Remarks - Satoshi Iso (RIKEN), Director of iTHEMS 10h20 - 11h20 SESSION 1 - Chair: Tetsuo Hatsuda (RIKEN) Yoshihiko Susuki (Kyoto University): Koopman resolvents in dynamical systems and control 11h20 -11h40 Free Discussions 11h40 - 13h00 Lunch Break & Discussions 13h00-14h00 SESSION 2 - Chair: Narumi Fujii (Institute of Science Tokyo) Alexandre Mauroy (University of Namur, Belgium): Analytic EDMD method for spectral analysis of fixed point dynamics 14h00 - 14h30 Coffee Break & Discussions 14h30 - 15h30 SESSION 3 - Chair: Tetsuo Hatsuda (RIKEN) Hiroya Nakao (Institute of Science Tokyo): Koopman operator analysis of coupled oscillator systems 15h30 - 16h00 Coffee Break & Discussions 16h00 - 17h00 SESSION 4 - Chair: Riccardo Muolo (RIKEN) Yuzuru Kato (Future University Hakodate): Analysis of quantum nonlinear oscillators on the basis of Koopman operator theory 17h00 - 17h05 Closing Remarks - Tetsuo Hatsuda, Chair of the Workshop 17h05 - 18h00 Free Discussions

会場: 研究本館 5階 535-537号室

イベント公式言語: 英語

Critical Phenomena on the Bethe Lattice

2026年3月18日(水) 16:00 - 18:00

Saswato Sen (沖縄科学技術大学院大学 (OIST) 博士課程)

We investigate the critical behavior of a family of Z2-symmetric scalar field theories on the Bethe lattice (the tree limit of regular hyperbolic tessellations) using both the non-perturbative Functional Renormalization Group and perturbation theory. Due to the hyperbolic nature of Bethe lattices, the Laplacian lacks a zero mode and exhibits a spectral gap. We demonstrate that closing the spectral gap via a modified Laplacian leads to novel critical behavior governed by interacting fixed points. This stands in contrast to the nearest-neighbor Ising model, which exhibits a phase transition with mean-field critical exponents. We further comment on the possible reasons for such a deviation.

会場: via Zoom / 研究本館

イベント公式言語: 英語