The RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), the College of Arts and Sciences of the University of Tokyo and the Faculty of Science of Kyoto University will launch a new inter-university collaborative online lecture system in April 2022, offering courses on various aspects of mathematical sciences to students in both faculties. In addition to faculty members from the University of Tokyo and Kyoto University, young researchers from RIKEN and other research institutes will give a series of lectures, which students can take as courses at their respective universities and earn credits. This new lecture format allows students to learn the fundamentals and applications of mathematical science, which form the foundation of modern society, from front-line researchers as early as their undergraduate years. At the same time, it enables the development of young human resources beyond the boundaries of universities. Active discussions between young researchers and students in class are expected to lead not only to the development of basic scientific research, but also to the development of human resources who will create innovations in society in the future.

For more information, please see the related link.

A research team led by Takemasa Miyoshi (Deputy Program Director, iTHEMS) has devised a new theory of control simulation experiments to study weather controllability.

Under a project led by the RIKEN Center for Computational Science, researchers have used computer simulations to show that weather phenomena such as sudden downpours could potentially be modified by making small adjustments to certain variables in the weather system. They did this by taking advantage of a system known as a “butterfly attractor” in chaos theory, where a system can have one of two states—like the wings of a butterfly—and that it switches back and forth between the two states depending on small changes in certain conditions.

To read more, please see the related link.

The annual in-house gathering entitled iTHEMS NOW and NEXT FY2021 was held on March 25th online. The gathering is an occasion that we discuss the current status and future perspectives on our research and organization. The event started with five keynote talks given by Takeru Yokota, Yalong Cao, Ryosuke Iritani, Ryo Namba, Keita Mikami. After a short break a session on the proper practices in conducting scientific researches followed during lunch time. In the session, the participants discussed their research practices in small groups and later shared their discussions with all. In the afternoon, each working group and study group made their progress reports. Program Director Hatsuda’s remarks concluded the gathering.

Hiroyasu Miyazaki (Visiting Scientist, iTHEMS) received "FY2021 RIKEN Excellent Achievement Award (RIKEN BAIHO Award)" on March 23, 2022 for his achievement on "Development of generalized theory of motives". Congratulations !

At the March 17th seminar , I presented my research. It was mainly an analysis of the phylogenetic position of orphan organisms (organisms whose phylogenetic position is unknown) based on large-scale sequence data, and in addition, I showed that huge lineages (Archaeplastida), including plants, are monophyletic. Although monophyly of Archaeplastida has been debated for many years, this study clarified that they are monophyletic and why they were not monophyletic in previous research. The seminar was very active, with many questions about the methods of phylogenetic analysis and biological questions.

The Quantum Matter Study Group invited Dr. Tiantian Zhang from Tokyo Institute of Technology to talk about the local and global topology for Tg-protected Z₂ Dirac points. In the beginning, by introducing the topological phase in the gapped and gapless systems, she discussed the conventional and Z₂ Dirac points. Surprisingly, she established gauge-invariant charge formula and bulk-surface correspondence for Z₂ Dirac points, which can give a full understanding about the topology of Tg-protected Z₂ Dirac points. Then, she proposed the first Z₂ Dirac material candidate Li2B4O7 for further exploration.

Reported by Congcong Le

I am a Ph. D candidate in Peking University, China, and I joined iTHEMS on April 1st 2022 as a student trainee. I am interested in understanding the interactions between hadrons from the fundamental theory, i.e., quantum chromodynamics (QCD). It is in some sense similar with determining the Coulomb interaction between two objects by calculating a simple integral using a pen and a piece of paper, like high-school students usually do in their physical class. However, as far as QCD is concerned, such an integral is too complicated to be done by using a pen and a piece of paper, thus I employ the so-called lattice QCD method to calculate such an integral by supercomputers. Once the interactions are determined from QCD, one can use them to various systems from nuclei to neutron star. I am very happy to join iTHEMS, and I look forward to interacting with people from various fields.

My name is Kotaro Murakami and have joined iTHEMS since April 2022 as a student trainee. My research is to solve the mystery of hadrons from the first-principle calculation of quantum chromodynamics (QCD). QCD is a theory describing the dynamics of quarks and gluons, and hadrons are composed of these particles. There are several hadrons we do not know how are created from quarks and gluons, which are called exotic hadrons. My ultimate goal is to identify all of the hadrons including exotic hadrons from QCD. I am working on the lattice QCD studies of baryon resonances from meson-baryon scatterings. I hope to have fruitful discussions in iTHEMS with not only people in particle physics or hadron physics but people in other fields.

My name is Xun Liu, and I joined iTHEMS in April 2022 as a student trainee. I am now involved in a PhD program at the University of Tokyo. My current research project and interest mainly lies in the field of two-dimensional conformal field theory, string theory, and string field theory. I am also interested in the relationship of these fields with formal mathematical topics, including group and representation theory, and analytical geometry. I am looking forward to interacting with mathematicians to form a more mathematical well-developed language in describing CFT and string theory.

Title: Diffeomorphisms of 4-manifolds with boundary and exotic embeddings
Author: Nobuo Iida, Hokuto Konno, Anubhav Mukherjee, Masaki Taniguchi
arXiv: http://arxiv.org/abs/2203.14878v1

Title: Femtoscopic study on $DD^*$ and $D\bar{D}^*$ interactions for $T_{cc}$ and $X(3872)$
Author: Yuki Kamiya, Tetsuo Hyodo, Akira Ohnishi
arXiv: http://arxiv.org/abs/2203.13814v1