イベント検索

Sex ratio theory for facultative parthenogens: from fortuitously optimal stick insects to the origin of haplodiploidy in Hymenoptera

2026年2月26日(木) 13:00 - 14:00

コーラ・クライン (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 訪問研究員)

First, I will present one of my PhD papers which focuses on sex ratios when females can reproduce both sexually and asexually. This paper features two models: an optimality model and an evolutionary invasion analysis. More generally, it shows my style of approaching evolutionary theory. After this, I will briefly discuss the work I plan to do in the next 6 months during my JSPS fellowship where I will focus on the evolution of more conventional X-chromosomes. Short Bio: I studied biology at the Free University in Berlin. My biology studies were mostly empirical but I attended several Bachelor courses for mathematicians (calculus and stochastics) and did my Master thesis in Zurich with Hanna Kokko, a theoretical evolutionary ecologist who studies a broad range of topics. In 2020, I then continued working in Hanna Kokko’s group for my PhD and moved with her from Zurich to Mainz in 2023. During my time with Hanna Kokko, worked on various topics centered around intraspecific diversity, including projects on sexual dimorphism, sex ratio theory, intralocus sexual conflict, and a female-limited color polymorphism in a butterfly. Since then, I started my first PostDoc in 2024 with Laura Ross in Edinburgh (UK) where I modelled how the unusual genetic systems of Scarid flies could have evolved, and have now started a 6 month JSPS fellowship with Ryosuke Iritani.

会場: 研究本館 435-437号室

イベント公式言語: 英語

Noninvertible symmetry protected topological phases on lattice

2026年2月25日(水) 10:30 - 11:30

Weiguang Cao (PD, Centre for Quantum Mathematics, University of Southern Denmark, Denmark)

The recent discovery of noninvertible symmetries—a radical extension of conventional symmetry—has challenged long-standing paradigms in condensed matter physics and quantum information and opened new territory in both theory and technology. Unlike ordinary symmetries, which can be inverted, these symmetries behave like projections (one-way operations) yet still strongly constrain quantum dynamics and enable new classes of phases and phase transitions. However, their role in organizing and stabilizing novel quantum phases remains poorly understood. One important example is a symmetry protected topological (SPT) phase, characterized by nontrivial edge modes and potential applications in quantum information. In this talk, I will discuss the classification of noninvertible symmetry-protected topological (NISPT) phases in both closed and open quantum systems using a duality-based method, and present concrete lattice realizations. These lattice models provide controlled playgrounds in which the physics of noninvertible symmetry can be explored numerically and, potentially, experimentally.

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

Quantitative phylogenomics

2026年2月24日(火) 13:00 - 14:00

ヘクター・バニョス (Assistant Professor, Department of Mathematics, California State University, USA)
ベンジャミン・テオ (Postdoc, Mathematical Analysis of Cellular Systems, University of Melbourne, Australia)

This session features two speakers: Hector Banos, Assistant Professor of Mathematics at California State University, whose research focuses on phylogenetic inference and network models, and Benjamin Teo, a Postdoctoral Researcher at the University of Melbourne, working on probabilistic and computational methods for continuous trait evolution on phylogenetic networks. See below for details. 【Talk 1】 Speaker: Hector Banos Title: Bringing a Knife to a Gunfight: Pitfalls of Phylogenetic Inference under Model Misspecification Abstract: Phylogenetic networks provide a flexible framework for representing evolutionary histories that include hybridization, introgression, and other reticulate processes. However, inferring such networks remains computationally and statistically difficult. Many current methods often scale only to restricted classes of networks. Consequently, researchers frequently analyze their data using simpler models (most commonly phylogenetic trees) even when there is strong evidence that the underlying evolutionary history is more complex. In this talk, we examine the impact of model misspecification on phylogenetic inference, focusing on situations in which data are generated by a complex network but are analyzed using simpler tree or network models. I then show how this mismatch can influence the topology of inferred trees, as well as the structure of inferred networks. These results highlight the limitations and the practical consequences of using simplified models for phylogenetic inference. 【Talk2】 Speaker: Benjamin Teo Title: Adapting cluster graphs for inference of continuous trait evolution on phylogenetic networks Abstract: I consider a new approach ("loopy belief propagation") for fitting Gaussian models on a phylogenetic network to explain the data observed across present-day species for a continuous univariate or multivariate trait. We previously showed [1] that a trait evolution model coupled to a network can be readily cast as a probabilistic graphical model, so that the likelihood can be efficiently computed using a dynamic programming framework ("belief propagation") defined on an auxiliary graph ("cluster graph") that is tree-structured. Even so, maximum likelihood estimation can grow computationally prohibitive for large complex networks. Belief propagation can be applied more generally to non-tree ("loopy") cluster graphs to compute a factored energy approximation to the log-likelihood. "Loopy" belief propagation may provide a more practical trade-off between estimation accuracy and runtime. However, the influence of cluster graph structure on this trade-off is not precisely understood. We conduct a simulation study using our Julia package PhyloGaussianBeliefProp [2] to investigate how varying the maximum cluster size of a cluster graph affects this trade-off. We discuss recommended choices for maximum cluster size, and prove the equivalence of likelihood-based and factored-energy based estimates for the homogeneous Brownian motion trait model. The talk is based on our preprint [3]. I will introduce the key concepts from the ground up.

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

Basic Conceptual and Mathematical Problems of QFT

2026年2月20日(金) 14:00 - 15:30

クリスティ・コウジ・ケリー

In this talk we discuss some of the most basic conceptual and mathematical difficulties that arise in the standard physics analysis of QFT. In particular we shall discuss the origin of UV divergences in QFT—pointing out that there is both a kinematic and a dynamic aspect to this problem, and that the standard physics explanation (’new physics’) only considers the latter—and suggest that despite the notoriety of the problem, UV divergences are essentially under control. Secondly we discuss Haag’s theorem—which ensures the nonexistence of the interaction picture and the triviality of the perturbative S-Matrix—and indicate how this is the most elementary manifestation of a series of infrared problems in QFT. Finally we will outline why the rigorous construction of path-integral measures is difficult. If we have time, we may discuss some difficulties associated with gauge theories such as the infraparticle problem of QED and the mass-gap problem of Yang-Mills theory.

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

Tunneling with physics-informed renormalisation group flows in the anharmonic oscillator

2026年2月20日(金) 10:00 - 11:00

Friederike Ihssen (Postdoctoral Fellow, Physics, Ruhr University Bochum, Germany)

The resolution of strongly correlated physical systems is computationally hard, but can be simplified enormously by a formulation in terms of suitable dynamical degrees of freedom. Within the functional renormalisation group framework, physics-informed renormalisation group flows (PIRG flows) [1] implement scale-dependent coordinate transformations that can be used to devise optimal expansion schemes around such degrees of freedom. Recently, we have applied PIRG flows to the anharmonic oscillator, with an emphasis on the weak coupling regime with its instanton-dominated tunnelling processes [2]. We show that the instanton physics behind the exponential decay of the energy gap is already covered in the first order of the derivative expansion of the PIRG. The crucial new ingredients in the present analysis are the use of the ground state expansion within PIRG flows, as well as precision numerics based on Galerkin methods. Our result a_inst = 1.910(2) for the decay constant is in quantitative agreement with the analytic one, a_inst = 1.886 with a deviation of 1%. This illustrates very impressively the capacity of the PIRG for fully capturing non-perturbative physics already in relatively simple approximations.

会場: via Zoom / 研究本館

イベント公式言語: 英語

Binary neutron Star Merger as a Probe of Hadron-Quark Transition

2026年2月19日(木) 14:00 - 15:00

黄 永嘉 (Research Associate, Purple Mountain Observatory, Chinese Academy of Sciences, China)

This seminar is a joint seminar between GWX-EOS and the iTHEMS-ABBL Joint Astro SG. The recent rise of multi-messenger astronomy—including radius measurements from NICER, tidal deformability constraints from gravitational-wave events GW170817, and first-principles calculations from chiral effective field theory (χEFT) and perturbative QCD—has significantly tightened constraints on the neutron star equation of state. These advances consistently point to a non-monotonic sound speed in dense matter, suggesting that the cores of massive neutron stars may host exotic phases such as quark matter. However, the masquerade effect in static neutron stars makes it difficult to directly probe the nature of the transition (e.g., a smooth crossover or a sharp phase transition) near the core through observation alone.

会場: 理化学研究所 和光キャンパス (メイン会場) / via Zoom

イベント公式言語: 英語

The sample complexity of species tree estimation: How many genes does it take to infer a species tree?

2026年2月19日(木) 13:00 - 14:00

Max Hill (Assistant Professor, University of Hawaiʻi, USA)

In this talk, I will discuss the problem of inferring an evolutionary tree from DNA sequence data. The main focus will be on the sample complexity of this problem---i.e., the question of how much data is required to achieve high probability of correct inference. After introducing a standard stochastic model of gene and DNA evolution, I will highlight some surprising features of DNA sequence data that complicate inference. Finally, I will present an impossibility result which takes the form of an information-theoretic lower bound on the minimum amount of data needed for accurate inference when genes exhibit variation in mutation rates. No prior knowledge of phylogenetics or information theory is assumed. Based on joint work with Sebastien Roch.

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

The Rectangular Peg Problem and microlocal sheaf theory

2026年2月17日(火) 14:00 - 15:00

池 祐一 (東京大学 大学院数理科学研究科 准教授)

The Square Peg Problem asks whether every Jordan curve in the plane contains four distinct points that form the vertices of a square. This problem was proposed by Toeplitz in 1911 and remains unsolved in full generality. It can be generalized to the Rectangular Peg Problem, which concerns the existence of inscribed rectangles with a prescribed aspect ratio. Recently, Greene and Lobb successfully applied techniques in symplectic geometry to the problem and obtained new results. In this talk, I will explain how microlocal sheaf theory allows us to further extend their approach and affirmatively solve the Rectangular Peg Problem for a large class of Jordan curves, including all curves of finite length. This is joint work with Tomohiro Asano.

会場: セミナー室 (359号室)

イベント公式言語: 英語

Monitoring the complexity and dynamics of mitochondrial translation

2026年2月12日(木) 16:00 - 17:00

脇川 大誠 (理化学研究所 開拓研究所 (PRI) 岩崎RNAシステム生化学研究室 リサーチアソシエイト)

Since mitochondrial translation leads to the synthesis of the essential oxidative phosphorylation (OXPHOS) subunits, exhaustive and quantitative delineation of mitoribosome traversal is needed. Here, we developed a variety of high-resolution mitochondrial ribosome profiling derivatives and revealed the intricate regulation of mammalian mitochondrial translation. Harnessing a translation inhibitor, retapamulin, our approach assessed the stoichiometry and kinetics of mitochondrial translation flux, such as the number of mitoribosomes on a transcript, the elongation rate, and the initiation rate. We also surveyed the impacts of modifications at the anticodon stem loop in mitochondrial tRNAs (mt-tRNAs), including all possible modifications at the 34th position, in cells deleting the corresponding enzymes and derived from patients, as well as in mouse tissues. Moreover, a retapamulin-assisted derivative and mito-disome profiling revealed mitochondrial translation initiation factor (mtIF) 3-mediated translation initiation from internal open reading frames (ORFs) and programmed mitoribosome collision sites across the mitochondrial transcriptome. Our work provides a useful platform for investigating protein synthesis within the energy powerhouse of the cell.

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

Finite-size effects on the QCD critical point

2026年2月9日(月) 15:30 - 17:30

Gyozo Kovacs (Research Fellow, Institute of Theoretical Physics, University of Wroclaw, Poland)

[Joint seminar hosted by QMS Team (iTHEMS) and FTR Team (R-CCS)] While effective approaches are important tools in the search for the QCD critical point, the physical systems they describe differ in several aspects from those in heavy-ion collisions and from unextrapolated lattice QCD. A primary discrepancy is the system size, which is infinite only in effective model calculations. Various implementations exist to account for the resulting finite-size effects. Beyond the frequently used methods, we present a comprehensive mean-field approach that allows for both infinite- and finite-size calculations, even within a complex parameter space. We discuss the general impact of finite-size effects on key observables, such as conserved charge fluctuations, and on the analytic structure of the thermodynamic potential. 15:30-16:30 Lecture 16:30-17:30 Discussion with coffee

会場: 研究本館 (メイン会場) / via Zoom

イベント公式言語: 英語

What can we learn from kilonovae about nucleosynthesis and high-density matter?

2026年2月9日(月) 14:00 - 15:15

オリバー・ユスト (Postdoctoral Researcher, GSI Helmholtzzentrum für Schwerionenforschung, Germany)

The electromagnetic transients accompanying neutron-star mergers (NSMs), called kilonovae, are powered by the radioactive decay of freshly synthesized heavy elements. As such they should contain rich information about the ejected matter and the properties of the extremely dense meta-stable neutron-star remnant formed right after the collision. However, extracting such information from observed kilonova light curves and spectra remains a challenging endeavor, which requires sophisticated models of various hydrodynamic processes and neutrino transport effects, detailed knowledge of nuclear and atomic physics, as well as complex radiative transfer calculations. In this talk I will report recent efforts from our "HeavyMetal" collaboration aimed at deciphering kilonovae.

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

Quantitative characterization of microbial diversity and environmental adaptation

2026年2月5日(木) 13:00 - 14:30

松本 美緒 (理化学研究所 開拓研究所 (PRI) 鈴木地球・惑星生命科学研究室 大学院生リサーチ・アソシエイト)
鈴木 志野 (理化学研究所 開拓研究所 (PRI) 鈴木地球・惑星生命科学研究室 主任研究員)

イベント公式言語: 英語

Development of a real-time object tracking and response system

2026年1月29日(木) 13:00 - 14:00

イザク・プラナス シッジャ (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)

I will introduce the real-time tracking software and automatic response system that we are developing: TracktorLive. We created a modular system to overcome several issues in close-loop experiments, with the aim to automatise mechanical stimulus delivery or time-consuming actions, and provide tools for VR experiments in animals. This tracker, coded as a Python package, separates the processes into server and client functions to run several processes in parallel, which minimises the frame processing time, and allows running on low-end computers. We hope to implement LLM or AI functions as server processes in the future.

会場: セミナー室 (359号室)

イベント公式言語: 英語

iTHEMS Cosmology Forum n°5 - Effective Field Theory approaches across the Universe

2026年1月29日(木) 10:00 - 17:00

青木 勝輝 (京都大学 基礎物理学研究所 基研特任助教)
野海 俊文 (東京大学 大学院総合文化研究科 准教授)
Lucas Pinol (CNRS Researcher, Laboratoire de Physique de l’École Normale Supérieure (LPENS), CNRS/École Normale Supérieure, France)

This fifth workshop will bring together researchers exploring the effective field theory (EFT) framework in diverse cosmological contexts (https://indico2.riken.jp/event/5435/overview). Topics will include EFT formulations of interacting dark matter and dark energy, open EFTs for gravity, and multi-field inflationary dynamics. By highlighting recent progress and open questions, the workshop seeks to bridge insights from the early and late universe through the unifying language of EFT. In addition to the invited talks, the workshop will feature a panel discussion designed to promote interaction between the speakers and participants. One of the key goals of this event is to foster collaboration among researchers working in neighboring fields, and to encourage participation from young and early-career researchers who are interested in, but may not yet have worked on, these themes. The workshop welcomes a broad audience with an interest in theoretical cosmology, gravitation, and quantum field theory. The workshops are organised by the Cosmology Study Group at RIKEN iTHEMS.

会場: 大河内記念ホール

イベント公式言語: 英語

DEEP-IN-iPI Joint Meeting

2026年1月26日(月) - 30日(金)

郭 星雨 (Lecturer, Institute of Quantum Matter, South China Normal University, China)
Gert Aarts (Professor, Department of Physics, Swansea University, UK)
施 舒哲 (Assistant Professor, Physics Department, Tsinghua University, Beijing, China)
Sung Hak Lim (Senior Researcher, Center for Theoretical Physics of the Universe (CTPU-PTC), Institute for Basic Science (IBS), Republic of Korea)
ジンヤン・リー (総合研究大学院大学 素粒子原子核コース 博士課程)
許 インイン (Research fellow, Department of Mathematics and Statistics, University of Helsinki, Finland)

The series of DEEP-IN meetings (Jan 26–30, 2026) are joint with UTokyo Institute for Physics of Intelligence (iπ), which is a multi-day scientific program bringing together researchers to explore quantum simulations, machine learning physics, and applications in particle and nuclear physics. The tentative schedule is, UTokyo-iπ Session (Venue: #512, Faculty of Science Bldg.1, School of Science, UTokyo) Day 1: Jan 26 (Mon) 14:30–16:00 Onset of Bjorken flow in a quantum many-body simulation of the massive Schwinger model, Shuzhe Shi Day 2: Jan 27 (Tue) 14:30–16:00 Physics of Diffusion Models, Gert Aarts 16:00–17:30 Discovering Symmetry from Energy-Based Diffusion Models, Jinyang Li RIKEN-iTHEMS Session (Venue: Seminar Room #359, Main Research Building) Day 3: Jan 28 (Wed) 14:30–16:00 Understanding Galactic Dark Matter with Generative Models, Sung Hak Lim 16:00–18:00 Free Discussion ML Physics-1 Day 4: Jan 29 (Thu) 10:00–11:30 Quantum Simulations of HEP and Beyond, Xingyu Guo 14:30–16:00 Physics of Machine Learning, Gert Aarts 16:00–17:30 Storage capacity of perceptron with variable selection, Yingying Xu Day 5: Jan 30 (Fri) 11:00–14:00: Free Discussion ML Physics-2

会場: via Zoom / セミナー室 (359号室) / 東京大学 本郷キャンパス 理学部１号館

イベント公式言語: 英語

New computational methods in quantum field theory 2026

2026年1月26日(月) - 28日(水)

Recent developments in quantum computers and related theoretical/technical advancements have brought attention to "new computational methods in quantum field theory" in the fields of high energy/nuclear physics. Main targets of this school are graduate students and postdocs. This school provides opportunities to discuss recent research trends and their applications through lectures by experts and presentations by participants. Lecturers: Junichi Haruna (University of Osaka) "Introduction to Quantum Error Correction (tentative)" Yoshimasa Hidaka (Yukawa Institute for Theoretical Physics/RIKEN iTHEMS) “Introduction to Hamiltonian Lattice Gauge Theory (tentative)” Tokiro Numasawa (University of Tokyo) "Open Majorana system (tentative)"

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Evolution of sterile soldier castes in aphids

2026年1月21日(水) 13:00 - 14:00

植松 圭吾 (慶応義塾大学)

This seminar is jointly organized with the RIKEN Center for Sustainable Resource Science (CSRS). Social evolution in aphids is tightly linked to the formation of galls on their host plants. Galls provide efficient colony defense and nutritionally rich feeding sites such that colony members need not forage outside, leading to high intra-group relatedness. Typically, social aphids form a gall on their primary host plant, after which winged morphs disperse to secondary host plants and establish a free-living, open colony. Remarkably, sterile soldier castes have independently evolved twice in these open colonies, where individuals live on plant surfaces without modifying their structure. These aphids raise intriguing questions about the prerequisites for eusocial evolution and the mechanisms by which two distinct social systems are maintained within a single genome. In this talk, I will first provide an overview of the life cycle and the diversity of altruistic behaviors in gall-forming aphids, and then present our studies of the evolution of a sterile soldier caste in aphids inhabiting open colonies. From a developmental perspective, we tested the hypothesis that the sterile soldiers evolved through the co-option of pre-existing soldier phenotypes in a gall, based on similarity in morphology, transcriptome and behavior. From an ecological perspective, we investigated the kin structure and altruistic behavior of young nymphs in the open colonies of pre-eusocial species, and demonstrate that young aphids exhibit altruism by yielding feeding sites to older kin. Together, we propose that the open colonies of social aphids provide an ideal model system for studying the evolution of altruism.

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

Classical Spinning Black Hole Scattering from Quantum Amplitudes

2026年1月15日(木) 14:00 - 15:30

Dogan Akpinar (Ph.D. Student, Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh, UK)

Scattering amplitudes have recently become a powerful tool for extracting classical observables in two-body gravitational dynamics, with direct relevance for current and future gravitational-wave experiments. In this talk, I will review how quantum scattering amplitudes can be used to obtain classical black hole scattering observables. A key focus will be the inclusion of spin effects, modelled by treating black holes as point particles in fixed-spin representations. This approach introduces a subtle ambiguity in the separation between classical and quantum information, which we resolve using our spin interpolation method. Leveraging this, we obtain, for the first time, the classical two-loop amplitude accurate to quartic order in spin, from which we extract physical observables such as linear and angular impulses using covariant Dirac brackets. Remarkably, the resulting amplitude obeys a spin-shift symmetry, remaining invariant under a shift of the black hole spin by the momentum transfer in the scattering process. Motivated by this structure, we examine the conserved quantities governing scattering and show that—at least asymptotically—the probe dynamics remain integrable through quartic order in spin. Under this asymptotic integrability, together with the spin-shift symmetry, we demonstrate that the quartic-in-spin radial action is fully determined by the aligned-spin sector. Taken together, these results advance our understanding of spinning black hole scattering and illuminate new structural features of Kerr dynamics.

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

Enhancing the methodological framework for inferring selection with ancient DNA: theoretical insights, improvements and comparison

2026年1月15日(木) 13:00 - 14:00

リュカ・ソール (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 特別研究員)

Over the past decade, the emergence of ancient DNA has opened new opportunities for studying evolutionary processes. However, inferring signals of selection from such data remains a methodological challenge since controlling for population stratification, admixture, and dynamically changing demographic histories, among other confounding evolutionary processes, is difficult. In this context, ancient DNA time series data, which have proliferated, have led to the development of methods based on two main frameworks: Hidden Markov Models and Generalized Linear Mixed Models. In this work, we aim to clarify how these frameworks relate to the classical Wright–Fisher model, enabling targeted modeling improvements and producing more relevant comparisons across methods.

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

Measuring evolutionary forces of cultural change

2026年1月13日(火) 14:00 - 15:30

ジョシュア・プロトキン (Walter H. and Leonore C. Annenberg Professor of the Natural Sciences, University of Pennsylvania, USA)

I will describe how to measure the forces that drive cultural change, using inference tools from evolutionary theory. We study time series data from large corpora of parsed English texts to identify what drives language change over the course of centuries. We also measure frequency-dependent effects in time series of baby names and purebred dog preferences. The form of frequency dependence we infer helps to explain the diversity distribution of names, and it replicates across the United States, France, Norway and the Netherlands. We find different growth laws for male versus female names, attributable to different rates of innovation, whereas names from the bible enjoy a genuine advantage at all frequencies. Frequency dependence emerges from a host of underlying social and cultural mechanisms, including a preference for novelty that recapitulates fashion trends in dog owners. Studying culture through the lens of evolutionary theory provides a quantitative account of social pressures to conform or to be different; and it provides inference tools that may be used in biology as genetic and phenotypic time series are increasingly available.

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