セミナー

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

From Data to Discovery: Chronobiology in Translation

2025年10月1日(水) 13:00 - 14:00

Bharath Ananthasubramaniam (Professor, Institute for Theoretical Biology, Humboldt University of Berlin, Germany)

Disruption of circadian rhythms is increasingly linked to a range of pathologies. To harness circadian biology for disease prevention and treatment, we must first establish causal relationships between rhythm disruption and the underlying clock mechanisms. This requires both the ability to quantify the “clock state” and to define what constitutes “disruption.” While significant progress has been made in model organisms, translating these insights to humans presents distinct challenges for quantitative chronobiology. In this talk, I will highlight how we have leveraged novel computational methods and high-throughput molecular datasets to begin addressing these obstacles.

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 Continuous Galactic Line Source of Axions: The Remarkable Case of 23Na

2025年9月30日(火) 14:00 - 15:00

ウィック・ハクストン (Professor, Department of Physics, University of California, Berkeley, USA)

While it is unusual for odd-A nuclear species to be abundant in massive stars, 23Na is an interesting exception. Typically 0.1 solar masses of 23Na is synthesized during the carbon burning phase of supernova and ONeMg white dwarf progenitors, then maintained at approximately 10^9 K for periods ranging up to 60,000 years. Under these conditions, 23Na can pump the thermal energy of the star into escaping axions: the mechanism is the Boltzmann occupation of and subsequent axion emission from the 440 keV level. We develop a galactic model to show that the resulting flux of line axions is continuous, arising from hundreds of contributing sources. As they travel through the intra-galactic magnetic field, some of these axions convert to detectable gamma rays. Consequently, future all-sky detectors like COSI will be able to set new limits on light axion-like particles. Other interesting aspects of these axions will be discussed.

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

Spontaneous quasiparticle creation in an analogue preheating experiment

2025年9月30日(火) 10:00 - 12:00

アモリ・ミケリ (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 特別研究員)

Abstract: First, I will briefly outline the motivations and concepts that underpin the analogue gravity program. Next, I will provide a detailed description of a specific experiment designed to simulate various features of the cosmological reheating era. Finally, I will present our recent experimental results from this setup, where we demonstrated the parametric creation of quasiparticle pairs from the quantum vacuum, drawing an analogy with the preheating phase of reheating.

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

The QCD phase diagram at finite densities

2025年9月29日(月) 13:30 - 15:00

Franz Sattler (Postdoc, Faculty of Physics, Bielefeld University, Germany)

I discuss recent progress towards calculating the QCD phase diagram at finite density using the functional Renormalisation Group (fRG). After introducing the fRG as applied to QCD, I explain some of the challenges encountered in functional approaches to the QCD phase diagram. Many of these can be resolved by recent developments of new numerical methods. In particular, the application of numerical hydrodynamics to RG flows and resolution of momentum dependences allow us to make progress towards quantitative access to the region of the conjectured critical end-point (CEP) of the QCD phase diagram. An interesting result is the appearance of new phases characterised by spatial modulations (the moat regime) and inhomogeneous condensates at high densities from a self-consistent first-principles calculation. For the near future, a clear program emerges to further pinpoint the CEP and its possibly modified nature using the fRG.

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

Confined Circumstellar Material as a Dust Formation Site in Type II Supernovae

2025年9月26日(金) 14:00 - 15:15

武井 勇樹 (京都大学 基礎物理学研究所 特定研究員)

Some massive stars undergo episodic mass loss shortly before core-collapse, producing dense circumstellar material (CSM) in their immediate surroundings. If the supernova (SN) ejecta strongly interacts with such CSM, narrow emission lines appear in the spectrum, classifying the event as Type IIn. In these cases, efficient radiative cooling forms a cold, dense shell (CDS), providing ideal conditions for dust condensation. Infrared observations of several SNe IIn have indeed confirmed newly formed dust. Recent time-domain surveys, however, suggest that compact and dense CSM, often termed “confined CSM”, is also present around a broader class of Type II SN progenitors with hydrogen-rich envelopes, beyond the traditional Type IIn subclass. This raises the possibility that dust formation in dense CSM is more common among core-collapse SNe than previously thought. In this talk, I will demonstrate that CDS formation occurs robustly across a wide parameter space for confined CSM using numerical simulations based on the open-source code CHIPS. I will also discuss the resulting dust mass and infrared emission, as well as the potential contribution of this process to the galactic dust budget.

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

The evolution of conditional dispersal promotes cooperation

2025年9月25日(木) 13:00 - 14:00

Iris Prigent (Ph.D. Student, Department of Ecology and Evolution, University of Lausanne, Switzerland)

Kin selection is an important mechanism for the evolution of cooperative behaviours across multiple taxa. While limited dispersal can foster kin selection by generating a genetic correlation between cooperating individuals, it also increases competition among relatives, constraining the evolution of cooperation. Prior theory has explored the co-evolution of dispersal and cooperation but typically assumes dispersal is independent of social cues. Here, we use mathematical modelling to examine whether socially-mediated dispersal, whereby individuals adjust their dispersal based on social context, can mitigate kin competition and thus enhance cooperation. We model the joint evolution of: (i) the probability of cooperating within social groups; and (ii) the probability of dispersing conditional on the number of individuals that have cooperated within the group, leading to a reaction norm for dispersal. We show that when the probability of dispersal increases with the number of cooperators, cooperation is favoured because it increases the fitness of relatives. The joint evolution of the two traits can lead to the differentiation of two types of individuals, one that always cooperates and another that never does. Although both types evolve dispersal norms such that they disperse more often when there are more cooperators in the group, cooperators evolve a steeper norm, reflecting greater sensitivity to their social environment. Our study shows that dispersal responses to the environment can vary between individuals based on their own social tendency, which can help explain why dispersal proclivities may differ between genotypes and between environments within a single population.

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

Data Assimilation for the Vicsek model

2025年9月25日(木) 13:00 - 14:00

Tomoharu Takaki (東京大学 大学院情報理工学系研究科 修士課程)

会場: 計算科学研究棟 R311 (メイン会場) / via Zoom

イベント公式言語: 英語

Lecture 2 on "Modular Structures in N=4 supersymmetric Yang-Mills theory"

2025年9月19日(金) 14:30 - 17:30

Daniele Dorigoni (Associate Professor, University of Durham, UK)

In this lecture series we present recent results in the study of exact correlation functions of half-BPS operators in N=4 supersymmetric Yang-Mills theory (SYM) averaged over the space-time insertion points. After presenting some basic properties of 1/2-BPS operators in N=4 SYM, we review how these integrated correlation functions can be obtained from a matrix model formulation of the N=4 path-integral. We then move to present two different integrated correlation functions of four superconformal primary operators of the stress-tensor multiplet which are holographically related to scattering amplitudes of 4-gravitons in type IIB superstring theory on an AdS_5 x S^5 background. We derive exact expressions both in the number of colours N, as well as in the complexified Yang-Mills coupling \tau. A key player in our discussion is electro-magnetic duality of N=4 SYM which provides strong constraints on the coupling dependence of such observables which, in particular, have to be real-analytic modular invariant functions of \tau. We then discuss the large-N fixed-\tau limit to show how these results can be interpreted on the dual stringy side. We also present some details on how these integrated correlator can be used to supplement the standard bootstrap approach leading to exciting coupling dependent bounds on the anomalous dimensions of non-protected operators in N=4 SYM, such as the Konishi operator. Lastly, we discuss an integrated correlation function involving two superconformal primary operators in the stress tensor multiplet in the presence of a half-BPS line defect operator, such as a Wilson line. Electro-magnetic duality is again fundamental in understanding the exact dependence from the coupling constant \tau. [OPTIONAL: If time and energy permit, I can also present some new results regarding integrated correlation functions of two light operators, dual to gravitons on the holographic side, and heavy giant graviton operators, dual to D3 branes extended on the background geometry]

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