セミナー

Introduction to Lean theorem prover

2025年10月31日(金) 14:00 - 17:00

水野 勇磨 (Postdoctoral Researcher, University College Cork, Ireland)

A theorem prover is a tool for the formalization of mathematics, that is, for rigorously expressing and verifying theorems and proofs on a computer. In recent years, the Lean theorem prover has seen progress in the formalization of a wide range of areas of mathematics. In this talk, I will explain formalization of mathematics in Lean from the basics and survey the formalized results achieved to date.

会場: via Zoom / セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

5th ComSHeL Seminar

2025年10月31日(金) 11:00 - 12:00

小谷 元子 (理化学研究所 領域総括)

Title: Discrete Geometric Analysis and its application to materials science Abstract: Discrete Geometric Analysis is a discrete version of Geometric Analysis. It is however not just its discretization but a development of methods to bridge discrete and continuum. I will explain those and share some applications to materials science with you.

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 (メイン会場) / via Zoom

イベント公式言語: 英語

Operational Quantum Frames: from quantum mechanics to quantum field theory and beyond

2025年10月30日(木) 16:00 - 17:00

Jan Głowacki (Postdoc, Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Austria)

In this talk I will begin with a concise overview of the development of the operational approach to quantum reference frames (QRFs), tracing the line from its foundational contributions to its most recent applications. I will then introduce the central ideas of the research direction that I am pursuing which aims at developing relational foundations for relativistic quantum physics. The starting point is the application of the operational QRF formalism to the context of the Poincaré group, and establishing connections between this emerging framework and existing formalisms in quantum field theory. This part of the talk will summarize results from a recent preprint written with Samuel Fedida [1]. I will conclude by outlining a number of open research directions, highlighting selected topics in more detail depending on the available time and the interests of the audience

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

Primordial black holes formation and its origin in inflation - Jianing Wang

2025年10月30日(木) 14:15 - 16:00

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

Primordial black holes (PBHs) are thought to form through gravitational collapse of regions with excessively large density in the early universe, and they could serve as seeds for the formation of galaxies. They are also considered one of the important candidates for cold dark matter (DM). Detecting and constraining the abundance of PBHs can provide an effective constraint on realistic inflationary models. In this talk, I will combine inflation models with gravitational waves (GWs) to discuss cosmological phenomena related to primordial black holes. In particular, I will emphasize a simplified toy model of inflation, which naturally enhances the small-scale scalar perturbations by gluing together two linear potentials with different slopes. The enhanced perturbations can not only generate primordial black holes but also emit gravitational waves through higher-order perturbations. This research demonstrates the significant potential of primordial black hole studies, and it naturally leads to a crucial question of how to accurately estimate the PBH abundance. In the latter part of the talk, I will introduce how to use peaks theory to estimate the abundance of primordial black holes. Our new method works well for any form of the power spectrum, and considering the use of more systematic statistical methods, we believe it is currently the most precise approach in the academic community.

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

Inferring Phylogenetic Networks in the Genomic Era

2025年10月30日(木) 13:00 - 14:00

孔 星植 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 研究員)

While phylogenetic trees (i.e., branching diagrams that depict the evolutionary history of different organisms) have been essential for understanding species evolution, they do not fully capture certain evolutionary processes, such as hybridization. In these cases, a phylogenetic network, which extends a phylogenetic tree by allowing two branches to merge into one and create reticulations, is needed. However, existing methods for estimating networks from genomic data become computationally prohibitive as dataset size and topological complexity increase. In this talk, I present the performance of popular computational methods that detect hybridization from genomic data as an alternative to the network inference, discussing their significance and limitations. I then explain how phylogenetic networks generalize trees to represent complex evolutionary histories and explore the biological interpretations that can be drawn from various branching patterns. Finally, I introduce PhyNEST (Phylogenetic Network Estimation using SiTe patterns), a novel method that efficiently and accurately infers phylogenetic networks directly from sequence data using composite likelihood. PhyNEST is implemented as an open-source Julia package and is available at https://github.com/sungsik-kong/PhyNEST.jl.

会場: 研究本館 3階 359号室 (メイン会場) / via Zoom

イベント公式言語: 英語

Sequence-encoded protein condensation: a statistical physics perspective

2025年10月23日(木) 13:00 - 14:00

足立 景亮 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 研究員)

イベント公式言語: 英語

Asymptotic gravity waves in core-collapse progenitor stars

2025年10月22日(水) 16:30 - 17:30

ルーシー・マクニール (京都大学 白眉センター 特定助教)

Internal gravity waves (IGW) are generically excited at convective boundaries inside stars. During the final months before a massive stars’ core-collapse, the excited IGW carry energy and angular momentum so large that the wave transport can e.g. completely set the rotation period of the neutron star remnant. In this talk, I present the first three-dimensional simulation of a core-collapse progenitor with which we can characterise IGW generation and transport preceding core-collapse. First I will show that the energy carried by convectively generated IGW in our simulation is described remarkably well by the established asymptotic theory, which utilizes e.g. the WKB approximation. But, the IGW’s subsequent propagation and dissipation depends very sensitively on the rotation. And in 3D, the equilibrium rotation patterns that develop are too complex to be captured in the established asymptotic theory for wave transport. I will present the rich nonlinear wave dynamics in our 3D simulation responsible for angular momentum transport and wave dissipation. I will propose that the angular momentum transport is governed by a “mean flow” interaction between global rotation and IGW transport. Mean flow interactions can explain the periodic Easterly <-> Westerly sudden reversal of winds at the equator on Earth, Saturn and Jupiter. If such reversals are realised in massive stars, it has implications for several exotic phenomena. This includes IGW driven mass loss outbursts observed in the final months before core-collapse supernova, and also gamma ray burst progenitor stars - which require very extreme rotation at core collapse.

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

Neural network wavefunctions for SU(2) lattice gauge theory in the Hamiltonian formulation

2025年10月22日(水) 15:00 - 16:30

Tom Spriggs (PostDoc, Kavli Institute of Nanoscience and QuTech, Delft University of Technology, Netherlands)

In this talk I will cover our recent preprint arXiv:2509.12323 where we propose a neural network approach to finding the ground state wavefunction of SU(2) lattice gauge theory. Specifically, we demonstrate that the use of bespoke SU(2)-gauge-equivariant neural network layers increases the extent to which our variational ansatz can represent the ground state of this system. During this talk I will contrast the Hamiltonian and Euclidean formalisms of lattice gauge theories, highlighting the promises that the former offers but also the difficulties: noting briefly the issues of parameterising the continuous Hilbert space that plague tensor network and quantum simulation approaches and how our approach alleviates this. I will try and present our method pedagogically as we are very interested in learning its uses but also the limits of its validity, before closing with some remarks on scaling to larger systems and different gauge groups.

会場: via Zoom

イベント公式言語: 英語

Simulating nonequilibirum quantum dynamics on Reimei

2025年10月21日(火) 10:00 - 12:00

早田 智也 (慶応義塾大学 医学部 准教授)

This is the third quantum computing gathering hold by quantum computing study group.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

Compact Association Schemes and Fourier Analysis

2025年10月17日(金) 15:00 - 17:00

中田 彬文 (広島大学 大学院先進理工系科学研究科 博士課程／日本学術振興会 特別研究員 DC)

Error-correcting codes are a fundamental tool in information and communication technologies. They can be viewed as collections of points in a space that are sufficiently far apart to allow error detection and correction. More broadly, coding theory studies good arrangements of points in spaces. This theory has been particularly developed in the frameworks of association schemes and compact homogeneous spaces, where harmonic analysis plays a central role. In this talk, we will begin with an introduction to error-correcting codes and then present compact association schemes, which we define as a generalization of these spaces in which harmonic analysis can be developed.

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

Bonded Knotted Structures and Applications

2025年10月16日(木) 16:00 - 18:00

Sofia Lambropoulou (Professor, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Greece)

We present the theory of bonded knots and bonded knotoids, as well as their algebraic counterparts, the theory of bonded braids and bonded braidoids. We also discuss some applications to the topological study of proteins.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

Particle-in-Cell Simulations on Collisionless Shocks and Particle Acceleration in Black Hole Coronae

2025年10月16日(木) 14:00 - 15:15

Nhat-Minh Ly (大阪大学 大学院理学研究科 博士課程)

Multiple nearby Active Galactic Nuclei have been reported as sources of high-energy neutrinos detected by the IceCube observatory. These results strongly suggest efficient proton acceleration to (sub-)PeV energies, likely within Black Hole (BH) coronae, given the lack of γ-ray counterparts. The acceleration mechanisms remain unconfirmed due to limited understanding of coronal environments and challenges in modeling hot, relativistic plasmas. Although diffusive shock acceleration (DSA) has been proposed, a self-consistent treatment incorporating detailed kinetic plasma effects has been lacking. In this study, we present the particle-in-cell (PIC) method as a first-principles approach to investigate particle acceleration by collisionless shocks under conditions inferred from multi-wavelength observations of BH coronae. Using large-scale 1D3V simulations, we surveyed shock parameters, focusing on underexplored effects such as initial ion–electron temperature ratios and trans-relativistic shock velocities, and found that collisionless shocks can form even in hot, low-Mach plasmas. These shocks accelerate protons up to ~100 TeV, consistent with the energies required for IceCube neutrino detections, across a wide range of coronal conditions. The shocks partition ~10% of dissipated energy into nonthermal protons and <1% into electrons, providing critical, observationally testable constraints on the plasma state of BH coronae.

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

Why complexity persists: Evolutionary dynamics of the amylase locus in primates

2025年10月16日(木) 12:30 - 13:45

Charikleia Karageorgiou (Postdoctoral Fellow, University at Buffalo, USA)

The amylase locus is among the most structurally variable regions of the human genome, frequently linked to starch digestion, metabolic traits, and dietary adaptation. Yet the causes of its recurrent duplication and exceptional variability remain unresolved. Why is this locus particularly prone to structural change? To address these questions, we analyzed 98 modern human genomes using long-read sequencing and optical mapping, alongside 53 high-quality primate assemblies. We identified 30 distinct amylase haplotypes in humans and documented more than 15 lineage-specific expansions and contractions across primates. Structural complexity appears to have been initiated by lineage-specific LTR insertions and subsequently shaped by non-allelic homologous recombination, with occasional contributions from microhomology-mediated break-induced replication. Independent duplications and salivary expression gains evolved repeatedly across primate lineages, but extensive within-species structural polymorphism is largely unique to humans. We further detected signatures of positive selection among primate paralogs, and dietary correlations with copy number suggest recurrent adaptive roles for amylase variation. The persistence of structural variation in this locus points to a unique combination of elevated mutational input, relaxed constraint, and ongoing selection, highlighting broader principles in the evolution of structurally unstable loci.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

Topological Field Theory Coupled to Parameter Spaces

2025年10月15日(水) 13:30 - 15:00

安藤 貴政 (京都大学 基礎物理学研究所 博士課程)

Topological quantum field theories (TQFTs) describe the IR fixed points of wide classes of gapped theories and are useful for studying many-body quantum phases of matter. In this talk, I will talk about TQFTs coupled to parameter spaces. I first explain the motivation for studying such TQFTs with parameter spaces from two perspectives: generalizing the description of the partition function with background gauge fields, and generalizing to invariants of many-body gapped phases over parameter spaces, known as the Berry phase. Then I will explain how these two are related by showing two physically motivated maps that connect them. The construction of these maps provides physical evidence for the Cobordism Hypothesis. I also discuss other related topics, such as the bulk-boundary correspondence. The talk is based on my ongoing work with Ryan Thorngren (UCLA).

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

Temporal Evolution of Crustal Stress at Volcanoes During Periods of Unrest

2025年10月14日(火) 10:30 - 12:00

Eric Newland (Research Fellow, Faculty of Mathematical & Physical Sciences, University College London, UK)

Eruptions that occur at volcanoes after periods of quiescence are difficult to forecast. Pathways that connect the source to the surface may have become sealed. The pressurisation of the source leads to the deformation of the crust. Initially the crust deforms elastically, strain is accommodated via ground movement and elastic strain energy is stored to the crust. Then, the deformation transitions to inelastic where strain is accommodated via brittle failure (volcano-tectonic event), and elastic strain energy is transferred from the crust. We present a novel method to estimate the temporal evolution of elastic strain energy and bulk stress during periods of unrest. We consider the transfer of energy using measurements of surface deformation and seismic activity. We evaluate the temporal evolution of crustal bulk stress and investigate the progression of deformation in the crust. We apply our method to the unrest at the Campi Flegrei caldera, Italy from 2011-2024, and the eruption of Sierra Negra, Galapagos, 2018. Our calculations reveal that the bulk stress follows a characteristic progression, in which the stress initially increases linearly with time prior to the onset of significant seismicity, consistent with elastic deformation. We then observe a transition to inelastic deformation, when rate of elastic strain energy lost via fracturing increases and eventually exceeds the rate of elastic strain energy transferred to the crust. This results in a decrease in the bulk stress stored in the crust with time, indicating a progressive weakening of the crustal material due to seismicity-induced damage. Comparison with laboratory experiments show the behaviour is consistent with bulk failure in extension and the potential formation of new pathways in the crust. Finally, we demonstrate how our method, along with the understanding of eruption precursors gained from the results, can be used to constrain deformation regimes at reawakening volcanoes after extended repose and to evaluate the hazard posed during periods of unrest.

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

イベント公式言語: 英語

Algebraic structures in QFT in the presence of a quantum reference frame

2025年10月9日(木) 14:00 - 15:00

Kasia Rejzner (Professor, Department of Mathematics, University of York, UK)

In this talk I will show how operational description of measurement with the use of quantum reference frames (QRF) affects the algebraic structure of quantum field theory (QFT). I will focus on the example of a quantum clock coupled to a QFT on de Sitter spacetime, previously discussed by Chandrasekaran, Longo, Pennington and Witten. This talk is based on my recent work with Chris Fewster, Daan Janssen, Leon Loveridge and James Waldron.

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

Homo lupo lupus est: Man is a wolf to wolves.

2025年10月9日(木) 14:00 - 15:00

Carlos Sarabia (Postdoctoral Researcher, Evolutionary Population Genetics Lab, Institute of Evolutionary Biology (IBE-CSIC), Spain)

The gray wolf (Canis lupus) is one of the most emblematic wild species in human history: revered as a symbol of strength and wildness, although unforgivably persecuted as a competitor and pest. Across Europe and much of Eurasia, wolves would still dominate as apex predators... were it not for millennia of human pressure. Today, their evolutionary trajectory is shaped not only by climate fluctuations and habitat loss, but also by a uniquely flexible species boundary. Due to their unique karyotype, canids can admix freely with other related species, a capacity that both threatens the genetic integrity of wild canids like wolves and enriches our understanding of hybridization as a driver of adaptation. In this talk, we will explore recent studies on wolf demography under human pressure and climatic change, with particular attention to admixture with domestic dogs and the consequences for their survival in increasingly anthropized environments. Finally, we will observe how the wolf's distinctive genomic architecture makes it a powerful model for testing population genetics theoretical frameworks and for applying state-of-the-art computational tools, offering new insights into the understanding of evolution as a force for change.

会場: via Zoom

イベント公式言語: 英語

Discovering and harnessing symmetry with machine learning

2025年10月6日(月) 16:00 - 17:30

Escriche Santos Eduardo (Ph.D. Student, Department of Computer Science, Technical University of Munich, Germany)

Incorporating symmetry-inspired inductive biases into machine learning models has led to many significant advances in the field, especially for its application to scientific data. However, recently, a trend has emerged that favors implicitly learning relevant symmetries from data instead of designing constrained equivariant architectures. In this talk, I will first introduce these different modelling alternatives, together with their associated benefits and limitations. Then, I will describe some examples of automatic symmetry discovery methods as a way of mitigating some of those limitations. Finally, I will present our recent work that integrates symmetry discovery and the definition of an equivariant model into a joint learnable end-to-end approach, which further alleviates some of the limitations of current equivariant modelling approaches.

会場: via Zoom

イベント公式言語: 英語

Quantum tunneling in the curved spacetime

2025年10月2日(木) 13:30 - 15:00

山口 昌英 (Director, Center for Theoretical Physics of the Universe, Institute for Basic Science, Republic of Korea)

False vacuum decay is theorized to have occurred frequently throughout the history of the universe, particularly during first-order phase transitions associated with spontaneous symmetry breaking. The decay rate of such a vacuum is governed by Euclidean bounce solutions, which can exhibit a wide range of configurations, even under fixed boundary conditions. In the absence of gravitational effects, it was established over four decades ago—under reasonable assumptions—that the most symmetric bounce solution, namely the O(4)-symmetric one, minimizes the Euclidean action. This renders it the dominant tunneling path in flat spacetime. However, when gravitational effects are taken into account—as is essential in cosmological settings—all prior studies have assumed, without rigorous proof, that the O(4)-symmetric bounce continues to minimize the action. This has remained a longstanding unresolved problem for more than forty years. In this work, we address this issue by employing the anti-de Sitter/conformal field theory (AdS/CFT) correspondence to determine the configuration with the lowest Euclidean action in a metastable AdS false vacuum. Within the Euclidean formalism of Callan and Coleman, we identify the most probable decay channel of the AdS vacuum. The AdS/CFT duality enables us to sidestep the technical challenges intrinsic to metastable gravitational systems. We demonstrate that the Fubini bounce in conformal field theory—which is dual to the Coleman–de Luccia (CdL) bounce in AdS—indeed minimizes the Euclidean action among all finite bounce solutions in a conformal scalar field theory. Consequently, under certain conditions, we establish that the CdL bounce yields the lowest action among all relevant configurations, including both large and thin-wall limits. Time permitting, we also discuss the prefactor of the decay rate, as obtained from one-loop quantum corrections.

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

What constitutes a gravitational wave in an expanding universe?

2025年10月1日(水) 16:00 - 17:30

Yi-Zen Chu (Professor, Department of Physics, National Central University, Taiwan)

Our understanding of gravitational waves produced by isolated astrophysical systems is primarily based on gravitational perturbation theory off a flat spacetime background. This leads to the common identification of gravitational radiation with massless spin-2 waves. In this talk, I will argue that gravitational waves may no longer be solely "spin-2" in character once the background spacetime is our expanding universe instead. As a result of the mixing between gravitational and other degrees of freedom, scalar "spin-0" gravitational waves may exist during the radiation-dominated epoch of our universe; as well as during its current accelerated expansion phase -- provided the main driver is not the cosmological constant, but some extra "Dark Energy" field. Moreover, during the radiation-dominated era, spin-0 Cherenkov gravitational waves may even be generated if its material source were traveling faster than 1/\sqrt{3}.

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