Visit by ASCENT-6E high school students (2026)

January 12 (Mon) 10:40 - 16:00, 2026

PROGRAMME Visit of students enrolled in the ASCENT Program at Chiba University Schedule 10:30-10:40 (10 min): Arriving procedure 10:40-11:00 (20 min) at the meeting room on the 4th floor, Main Research Building Introduction of students (to hear their names and scientific fields of interest). We will provide colour-coded badges for them to write their names, with each colour representing their field of interest (e.g., blue for biology, green for math, red for physics). 11:00-11:10 (10 min) Bathroom break 11:10-12:00 (50 min) at the meeting room on the 4th floor, Main Research Building First set of talks by iTHEMS members (10 min each) Catherine Beauchemin (Physics, biology) Gen Kurosawa (Biology) Yuta Sekino (Physics) Isaac Planas-Sitja (Biology) Wei-Hsiang Shao (Physics) 12:00-13:30 (90 min) at Common Space on the 4th floor of Main Research Building Discussion Lunch with students 13:30-14:20 (50 min) at the meeting room on the 4th floor, Main Research Building Second set of talks by iTHEMS members (10 min each) Ryo Namba (Physics) Sungsik Kong (Biology) Kenji Okubo (Biology) Steffen Backes (Physics) Jose Gutierrez (Biology) 14:20-14:30 (10 min) at the meeting room on the 4th floor, Main Research Building Brief overview of iTHEMS and RIKEN programmes (C.Beauchemin) (e.g., JRA, IPA, SPDR, RS/SRS) 14:30-14:40 (10 min) Bathroom break 14:40-14:55 (15 min) at the meeting room on the 4th floor, Main Research Building Short statements by Prof. Jun Nomura, Prof. Koji Tsuji, Prof. Kohei Watanabe, Prof. Yukiharu Akimoto, ASCENT program coordinators Qian Wang and Hina Morishige, graduate student Rin Chinen. 14:55-16:00 (65 min) at Common Space on the 4th floor of Main Research Building Informal discussions among ASCENT program students and iTHEMS members over some snacks and coffee. iTHEMS members will spread out across different areas in the common space on the 3rd floor and display posters or conduct activities to facilitate discussion.

Venue: #435-437, Main Research Building

Event Official Language: English

Median-based estimators for randomized quasi-Monte Carlo integration

January 9 (Fri) 15:00 - 17:00, 2026

Kosuke Suzuki (Associate Professor, Yamagata University)

High-dimensional numerical integration is a ubiquitous challenge across various fields, from mathematical finance to computational physics and Bayesian statistics. While standard Monte Carlo (MC) methods are robust, their probabilistic error convergence rate of $O(N^{-1/2})$ is often insufficient for demanding applications. In this talk, I will introduce Quasi-Monte Carlo (QMC) and Randomized QMC (RQMC) methods, which offer a powerful framework for accelerating integration using low-discrepancy point sets. A key advantage of this deterministic approach is its ability to achieve a convergence rate of $O(N^{-1+\epsilon})$, significantly outperforming the standard MC rate. The second part of the talk will focus on the construction of point sets, specifically lattice rules and digital nets. I will explain how these methods achieve higher-order convergence rates, faster than $O(N^{-1})$, for sufficiently smooth integrands. I will also discuss their randomized variants and demonstrate how RQMC with mean-based estimators provides practical error estimation while maintaining high-order convergence. Finally, I will discuss recent progress in RQMC involving median-based estimators. I will highlight how these estimators achieve almost optimal convergence rates for various function spaces without requiring prior knowledge of the integrand.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Higher Gauge Structures and Invariant Action Principles

January 6 (Tue) 15:15 - 16:15, 2026

Sebastián Salgado (External Researcher, Instituto de Alta Investigacion, Universidad de Tarapaca, Chile)

I present the systematic construction of gauge theories based on free differential and L-infinity algebras. This provides a consistent algebraic framework for constructing gauge-invariant theories whose field content is extended by higher-degree differential forms as gauge potentials. I derive explicit expressions for the corresponding extended Chern-Simons actions and the generalized anomaly terms that emerge from them. Possible applications to gravity and supergravity will also be discussed.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Invitation to Random Tensor Models: from random geometry, enumeration of tensor invariants, to characteristic polynomials

January 6 (Tue) 13:30 - 14:30, 2026

Reiko Toriumi (Associate Professor, Okinawa Institute of Science and Technology Graduate University (OIST))

I will introduce random tensor models by first reviewing their motivation coming from random geometric approach to quantum gravity. Then, I will selectively present some of the interesting research results, by highlighting recent results on enumeration of graphs representing tensor invariants, and reporting our recent work on a new notion of characteristic polynomials for tensors via Grassmann integrals and distributions of roots of random tensors. The latter two are based on arXiv:2404.16404[hep-th] and arXiv:2510.04068[math-ph]

Venue: #359, 3F, Main Research Building (Main Venue) / via Zoom

Event Official Language: English