Cautionary tales in data analysis from gravitational-wave astronomy

2026年4月23日(木) 13:00 - 14:00

キップ・カンノン (東京大学 ビッグバン宇宙国際センター (RESCEU) 教授)

We'll look at signal detection in noisy data, and at Bayesian inference in astrophysical inverse problems. We'll look at the form these problems take in the context of gravitational-wave astronomy, but we'll focus on where attempts at solutions have gone wrong. The mistakes we make transcend disciplines, and hopefully by shining light on them others can be helped to avoid making them as well.

会場: 研究本館 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

The math that shows a perfect democracy is impossible

2026年4月23日(木) 10:30 - 11:30

ブライアン・アンドリュー・ミンツ (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 数理社会科学チーム 特別研究員)

Groups need to make decisions, and there are a wide variety of ways this can be done, each maximizing different notions of fairness. Social Choice Theory provides a mathematical framework to investigate these possibilities rigorously. Infamous for its many impossibility results, this topic reveals some fundamental limits to democracy. Beyond this, we'll discuss potential resolutions to these problems, as well as their real world implications.

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

Seeing Photons, from Einstein to Bohr to Hanbury Brown-Twiss and related Hong-Ou-Mandel Interference Phenomena

2026年4月22日(水) 15:00 - 16:30

ゴードン・ベイム (Professor Emeritus, University of Illinois, USA)

Why do we believe that the electromagnetic field is quantized, and photons exist? This talk will focus on two ways that the quantization of the electromagnetic field manifests itself in interference experiments. Bohr, who initially doubted photons after Einstein's initial proposal of the photon to explain the photoeffect, eventually proposed a thought experiment showing that the consistency of elementary quantum mechanics at the level of two slit diffraction requires the quantization of the electromagnetic field. In addition, as I will argue, both Hanbury Brown-Twiss interferometry and the closely related Hong-Ou-Mandel effect provide yet another way to see that the electromagnetic field must be quantized.

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) Journal Club

2026年4月22日(水) 14:00 - 15:00

Please check the papers and post anything interesting in the #phys_journal_club Slack channel!

会場: 研究本館 4階 共有スペース

イベント公式言語: 英語

Quantum Computing of Molecular Properties for Fundamental Physics

2026年4月21日(火) 16:30 - 18:00

プラディヨット・プリタム・サフー (東京大学 大学院理学系研究科 大学院外国人研究生)

This is the self-introduction talk by Pradyot Pritam Sahoo. Pradyot is a Student Trainee in iTHEMS.

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

Quantum generative learning via diffusion

2026年4月21日(火) 10:00 - 11:00

Zhang Bingzhi (PostDoc, University of Southern California, USA)

Deep generative models are key-enabling technology to computer vision, text generation, and large language models. Generative models for quantum data offer a promising route toward learning and preparing complex quantum-state ensembles. In this talk, I will introduce the quantum denoising diffusion probabilistic model (QuDDPM) [1], which adapts the diffusion-model idea to quantum systems through a forward randomization process and a trainable backward denoising dynamics. I will discuss how this framework enables stepwise learning of target quantum state ensembles and demonstrate its capabilities in various learning tasks. I will then present its extension to mixed states to eliminate the need for scrambling [2]. I will conclude with a brief discussion of recent results on scaling laws of quantum information lifetime in monitored quantum dynamics, emphasizing how mid-circuit measurements can maintain information and provide useful intuition for measurement-assisted quantum machine learning.

会場: via Zoom

イベント公式言語: 英語

Challenges in virology & neurodegeneration: improving experimental procedures and theoretical insights

2026年4月20日(月) 14:00 - 15:00

カトゥリン・ボシゥメン (理化学研究所 数理創造研究センター (iTHEMS) 副センター長)

After repeatedly finding errors in experimental data provided by collaborators, my group developed an online tool (midSIN, https://midsin.roadcake.org/) to improve estimating the concentration of infectious viruses in samples. This led to an unexpected new collaboration with researchers working to measure the concentration of aggregating fibrils in samples from patients suffering from neurodegenerative diseases such as Dementia with Lewy Body and Parkinson's. In the first part of my talk, I will introduce the basics of how infectious virions and aggregating fibril concentrations are measured experimentally, and discuss challenges in tackling these assays' limitations to improve their accuracy and sensitivity. In the second part of my talk, I will discuss the challenges we face in trying to identify the type and minimal number of experimental measurements required to predict the severity and transmission efficacy of diverse influenza viruses collected as part of pandemic surveillance efforts. I hope you will join the talk to learn of these challenges and consider contributing new ideas or approaches to overcome them.

会場: 研究本館 4階 435-437号室とZoomのハイブリッド開催

イベント公式言語: 英語

Analytical parametrization of the primordial power spectrum in effective Loop Quantum Cosmology

2026年4月20日(月) 13:00 - 14:00

Almudena Sánchez Guillén (Ph.D. Student, Institute of Structure of Matter (IEM-CSIC), Spain)

We investigate the imprints on the angular power spectra of cosmological perturbations of a pre-inflationary bounce phase, as described by the hybrid and dressed metric approaches to loop quantum cosmology. For this purpose, we derive a new parametrization of the primordial power spectrum at the end of the inflationary regime. Apart from slow-roll coefficients and cosmological parameters that are present in the standard cosmological scenario without quantum modifications, this parametrization additionally depends only on pre-inflationary physics. More specifically, we find a dependence on the number of e-folds during the bounce epoch and on a characteristic suppression scale which, given the e-folds accumulated during cosmic evolution, is determined by the energy density at the bounce.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

iTHEMS × academist オンラインイベント「数理で読み解く科学の世界 2026」

2026年4月18日(土) 10:00 - 15:30

小泉 淳之介 (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)
福島 理 (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)
洪 木子 (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)
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)

「数理で読み解く科学の世界」は、2020年より毎年4月に開催しているオンラインイベントです。主催のiTHEMSは、「数学」を共通言語として、物理、生物、宇宙などさまざまな科学分野の横断的な研究をしており、イベントでは、iTHEMS所属の若手研究者4名が最先端の研究について中学生や高校生にもわかるように30分程度の講演を行います。また、一般参加者からの質問やコメントを受け付ける時間も設けています。 詳細、参加お申し込みは、関連リンクをご覧ください。 日時：2026年4月18日（土）10:00〜15:30（開場 9:45） 場所：Web会議サービス「Zoom」（申込者に事前に招待URLをお伝えいたします） 参加費：無料 対象者：中学生・高校生、社会人（どなたでもご参加いただけます） 主催：iTHEMS 共催（企画・運営・宣伝）：アカデミスト株式会社 特別協力：NPO法人 数理の翼 タイムスケジュール： 10:00～　開始の挨拶・イベント概要説明 10:15～　講演「幾何学的に見る整数論の世界」小泉 淳之介 博士 11:15～　講演「対称性がつむぐ量子のふるまい」福島 理 博士 12:10～　昼休み企画 「AI時代の知性と学び　−甘利俊一×磯暁」 出演：甘利 俊一 博士（理研栄誉研究員、帝京大学先端総合研究機構 特任教授）、磯 暁 博士（理研 iTHEMS センター長） 進行：篠崎 菜穂子（フリーアナウンサー） 13:05～　講演「宇宙の始まりとインフレーション理論」洪 木子 博士 14:05～　講演「AIと進化で考える生命のしくみ ― 遺伝子ネットワークから生まれる遺伝の法則 ―」大窪 健児 博士 15:00〜　アフタートーク 15:30　　終了予定

会場: via Zoom

イベント公式言語: 日本語

TJR-iTHEMS Joint Seminar: Golden Age of Neutron Stars

2026年4月17日(金) 16:00 - 17:00

ゴードン・ベイム (Professor Emeritus, University of Illinois, USA)

This is a TJR-iTHEMS Joint Seminar supported by ASPIRE Program ABSTRACT Neutron stars were first posited in the early thirties, and discovered as pulsars in the late sixties; however we are only recently beginning to understand the matter they contain. I will describe the ongoing development of a consistent picture of the liquid interiors of neutron stars, now driven by ever increasing observations as well as theoretical advances. These include observations of heavy neutron stars of about 2.0 solar masses and higher; ongoing inferences of masses and radii by the NICER telescope; and observations of binary neutron star mergers, through gravitational waves as well as across the electromagnetic spectrum. Theoretically an understanding is emerging in QCD of how nuclear matter can turn into deconfined quark matter, which I will illustrate with modern quark-hadron crossover equations of state. BRIEF BIO Gordon Baym is a Professor of Physics at the University of Illinois. Educated at Cornell and Harvard, he spent two years at the Niels Bohr Institute. His interests range from matter under extreme conditions to ultracold atomic physics, astrophysics, and nuclear physics. A pioneer in the study of pulsars and neutron stars, he is a member of the U.S. National Academy of Sciences and received the APS Medal for Exceptional Achievement in Research, the Hans Bethe and Lars Onsager Prizes, and the Eugene Feenberg Memorial Medal.

会場: 大阪大学豊中キャンパス H701

イベント公式言語: 英語

第32回 MACSコロキウム・2026年度MACS学生説明会

2026年4月17日(金) 14:45 - 18:30

冨田 夏希 (京都大学 大学院理学研究科 附属サイエンス連携探索センター (SACRA) 准教授)

14:45-15:00 ティータイムディスカッション 15:00-16:00 冨田 夏希（京都大学大学院理学研究科附属サイエンス連携探索センター 准教授）「質量の起源を探る」 16:15-17:20 2026年度MACS学生説明会 17:30-18:30 継続討論会

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

イベント公式言語: 日本語

RIKEN Seminar: Formulation of Life Phenomena from Quantum Theory

2026年4月16日(木) 14:00 - 16:05

13:45 Opening 14:00-14:05 Introduction Atsushi Iriki (Teikyo University Advanced Comprehensive Research Organization Division of Artificial Intelligence, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS)) 14:05-14:35 "Interpretation of Life Phenomena Using Quantum Wave Functions and Field Theory" Kazuhiro Sakurada (Keio University Medical School and RIKEN Center for Integrative Medical Sciences (IMS), Predictive Medicine Special Project (PMSP)) 14:35-14:45 Q&A 14:45-15:30 "Bridging neurophysiology and quantum-like cognition" Andrei Khrennikov (Center for Mathematical Modeling in Physics and Cognitive Sciences Linnaeus University) 15:30-15:45 Q&A 15:45-16:00 "Quantum-Like Measurement" Masanao Ozawa (RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), RIKEN TRIP FQSP, and Nagoya University) 16:00-16:05 Closing Remarks Satoshi Iso (Director, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS)) Host Laboratory: Predictive Medicine Special Project, RIKEN Center for Integrative Medical Sciences (IMS) / RIKEN Center for Interdisciplinary Theoretical and Mathematical Science (iTHEMS) *Registration is required by April 14 via the registration form. Contact: Predictive Medicine Special Project (pmsp-web@ml.riken.jp)

会場: 理化学研究所 和光キャンパス 脳科学池の端研究棟（建物番号C56）3階305

イベント公式言語: 英語

Searching For Anomalies with Foundation Models

2026年4月16日(木) 14:00 - 15:30

Vinicius Massami Mikuni (名古屋大学 素粒子宇宙起源研究所 (KMI) 准教授)

This is a joint seminar with Institute for Physics of Intelligence (iπ), UTokyo Anomaly detection relaxes the assumptions of how new physics should look and extends the reach of what we can discover. However, interpreting the data and estimating backgrounds remains a challenge. In this new work, we investigate anomalous events selected by the OmniLearned Foundation model across different model sizes, performing a full analysis using CMS Open Data. Surprisingly, models of different sizes, trained on the same data with the same loss functions, select entirely different collisions. In particular, the large OmniLearned model (500M parameters) selects events that are not well described by our background model.

会場: 東京大学 本郷キャンパス 理学部１号館 (メイン会場) / via Zoom

イベント公式言語: 英語

Understanding Biological Clocks Using Methods from Applied Mathematics and Theoretical Physics

2026年4月16日(木) 12:30 - 13:30

黒澤 元 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 専任研究員)

Imagine that you are in a room with no information about time. The room is located in a cave, where temperature and light intensity remain constant. In such an environment, would you be able to wake up tomorrow or the day after? In fact, most humans can wake up at roughly similar times on successive days. This is because we possess internal daily rhythms, known as circadian rhythms. Biological experiments have shown that such rhythms are not unique to humans, but are shared by many species on Earth. In this talk, I will introduce some open problems related to these daily rhythms, and discuss approaches based on dynamical systems theory and the renormalization group method, from the perspectives of applied mathematics and theoretical physics.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

iTHEMS NOW & NEXT 2026

2026年4月13日(月) - 14日(火)

We will hold an annual in-house gathering, “iTHEMS NOW & NEXT,” for FY 2026. The event provides a great opportunity for all iTHEMS members, including visiting researchers and, in particular, new arrivals, to gain a comprehensive overview of iTHEMS’s current activities and future directions. The detailed program will be announced in due course, but there will be poster sessions for all members, so please be ready to present one.

会場: 理化学研究所和光キャンパス 本部棟2階大会議室 (メイン会場) / via Zoom

イベント公式言語: 英語

From Classical Definiteness to Geometric Predictability: Complementarity, Coherence, and Thermodynamic Triality

2026年4月10日(金) 15:30 - 17:00

Ezra Acalapati Madani (Ph.D. Student, Laboratoire de Physique de l'École Normale Supérieure, France)

Wave–particle complementarity is one of the central principles of quantum mechanics, traditionally quantified through the Englert–Greenberger–Yasin relation between which-way information and interference visibility. In higher-dimensional and resource-theoretic settings, however, visibility is no longer unique, and it becomes natural to reformulate complementarity in terms of basis-dependent predictability, coherence, and mixedness. In this talk, I present two related works along this line. First, I discuss an exact complementarity relation between classical definiteness and quantumness, where definiteness is defined operationally through the resilience of a quantum state under nonselective dichotomic yes/no measurements, while the complementary quantum contribution is quantified using a Kirkwood–Dirac-based notion of coherence/interference motivated by recent KD-based coherence measures. Second, I introduce a geometric predictability defined by the Bures distance between the dephased state and the maximally mixed state. This predictability depends only on the observed measurement statistics and admits a closed form in terms of the Bhattacharyya overlap. For pure states, it satisfies an exact complementarity relation with nonclassical Kirkwood–Dirac coherence; for mixed states, this motivates a convex-roof extension whose operational meaning is the classically irreducible part of measurement randomness, with implications for guessing probability and min-entropy. Finally, motivated by the decomposition of entropy production into population and coherence contributions in quantum thermodynamics, and by standard wave–particle–mixedness triality relations, I show how the usual predictability–coherence duality can be promoted into a triality relation involving predictability, coherence, and mixedness. Altogether, the talk connects wave–particle duality, coherence resource theories, operational guessing tasks, and thermodynamic balance relations within a unified framework.

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

Clumpy Outflows from Super-Eddington Accreting Black Holes

2026年4月10日(金) 14:00 - 15:15

Haojie Hu (筑波大学 JSPS海外特別研究員)

Recent advances in X-ray spectroscopic observation have enabled researchers to reveal distinct clumpy structures in the super-Eddington outflows from the supermassive black hole in PDS 456 (XRISM Collaboration 2025), initiating detailed investigation of fine-scale structures in accretion-driven outflows. In this talk, I will introduce our high-resolution, two-dimensional radiation-hydrodynamics simulations with time-varying and anisotropic initial and boundary conditions that reproduce clumpy outflows from super-Eddington accretion flows. The resulting clumpy outflows extend across a wide range of radial distances and polar angles, exhibiting typical properties such as a size of ~10 rg (where rg is the gravitational radius), a velocity of ~0.05–0.2 c (where c is the speed of light), and about five clumps along the line of sight. Although the velocities are slightly smaller, these characteristics reasonably resemble those obtained from the XRISM observation. The gas density of the clumps is on the order of 10^-13–10^-12 g cm^-3, and their optical depth for electron scattering is approximately 1–10. The clumpy winds accelerated by radiation force are considered to originate from the region within <300 rg.

会場: 研究本館 2階　220号室 (メイン会場) / via Zoom

イベント公式言語: 英語

Biology Starter Meeting & Welcome 4 New Members!

2026年4月9日(木) 13:00 - 15:00

アルバ・ニエト エレディア (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)
鳥取 岳広 (理化学研究所 脳神経科学研究センター (CBS) 基礎科学特別研究員)
マリア・イヴォニナ (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)
平澤 さつき (北海道大学 大学院情報科学院 博士課程)

This is a special 2 h event of our newly renewed Biology Study Group! This year, 4 new members are joining iTHEMS Biology. They will each give us a 15 min introduction to their research. All participants will also take 2-3 min to introduce themselves and their research topic to the new members. If time permits, we'll hold a brief organizational meeting to review the running of the biology seminars in the new fiscal year. We strongly encourage all iTHEMS members, not just biology-interested ones, to join our session at least in the 1st hour, to meet the new members and learn about their research.

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

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