iTHEMS Weekly News Letter


Dr. Ryosuke Iritani thumbnail
Dr. Takashi Okada thumbnail

Dr. Ryosuke Iritani and Dr. Takashi Okada received 15th Young Scientist Award of JSMB


It is our great pleasure to inform you that 15th Young Scientist Award (Japanese Society for Mathematical Biology) was awarded to our iTHEMS colleagues, Ryosuke Iritani for his contribution to the theory of evolutionary ecology and Takashi for his contribution to the theory of chemical reaction networks. Many congratulations to Ryosuke and Takashi !!


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Dr. Shingo Gibo received the Best Poster Award of the Japanese Society of Chronobiology


Dr. Shingo Gibo received the Best Poster Award of the Japanese Society of Chronobiology. The title of the poster is "Analysis of the circadian period and phase synchronization based on waveform". Congratulations!

This is an abstract of the awards:
The circadian clocks are based on gene-activity rhythms with approximately 24-hour period, and its temporal waveforms are of various shapes. We theoretically showed that the waveform distortion contributes to the circadian period stability to temperature and entrainment to the environment cycles. Furthermore, by using the renormalization group method, which is developed in theoretical physics, we found that this relation between waveform and period holds not only for the circadian clock but also for many types of nonlinear oscillator models, including van der Pol and Lotka-Volterra model. This study is collaborated with physicists, Drs. Teiji Kunihiro (Kyoto University) and Tetsuo Hatsuda (iTHEMS).

Hot Topic

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Farewell message from Dr. Genki Ouchi


Hello. I am Genki Ouchi, a special postdoctoral researcher in iTHEMS. I am leaving iTHEMS and moving to graduate school of mathematics, Nagoya university as an assistant professor.

I joined iTHEMS on April 2018. Since then, it has been two and a half years. I learned a lot of things from iTHEMS. Before I came to iTHEMS, I was just an “algebraic geometer”. I studied only algebraic geometry and related topics. After joining iTHEMS, I got opportunities to learn other topics in mathematical science. Especially, I study network science with mathematicians, physicists and network scientists now. With an experience at iTHEMS, I become a “mathematician”. I wish that interdisciplinary activities in iTHEMS bear fruit over the long run.

I would like to thank all iTHEMS members for your kind support and help. I am looking forward to seeing you again.

Hot Topic

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Farewell message from Dr. Kenta Sato


Hello. I am Kenta Sato, a Special Postdoctral Resercher at iTHEMS. I am moving to Kyusyu University as an assistant professor. It is a great pleasure for me to spend one and a half years at iTHEMS because I have been stimulated by the open atmosphere of iTHEMS and by the energetic activities of each member. It helps me to broaden my perspective. I would like to say thanks to everyone in iTHEMS. I am looking forward to seeing the successful development of iTHEMS in the future.

Upcoming Events


Dr. Toshihiro Ota thumbnail

Math-Phys Joint Seminar

TQFT, integrable lattice model, and quiver gauge theories

October 2 at 16:00 - 18:00, 2020

Dr. Toshihiro Ota (Student Trainee, iTHEMS / Graduate School of Science, Osaka University School of Science)

- 1st part (math): In physics literature, “lattice models” appear quite often as mathematical models of physical systems, e.g. Ising model, vertex models, lattice gauge theory. The aim of the 1st part is to introduce ‘what is (T)QFT,’ ‘what is lattice model,’ and ‘what does integrability mean’ in the language of mathematics. In turn, they will play a crucial role in the 2nd part of my talk. I also hope that this will lead to a good exchange among us, especially between physicists and mathematicians.

- 2nd part (physics): In the 2nd part, I would like to explain where an integrable lattice model may come from, especially for people in the physics background. I will show a certain class of integrable lattice models is realized by Wilson-’t Hooft lines in 4d quiver gauge theories. I will also explain a bit how these gauge theories are constructed from brane configurations in string theory. String dualities allow us to relate the original 4d setups to 4d partially topological Chern-Simons theory, which is a partial TQFT and generates integrable lattice models.

Venue: via Zoom

Event Official Language: English


Forefront of Modern Science: Frontiers in Mathematics, Astronomy, Physics, Biology and Computation thumbnail

Forefront of Modern Science: Frontiers in Mathematics, Astronomy, Physics, Biology and Computation

October 2 at 16:20 - 17:50, 2020

Dr. Tetsuo Hatsuda (Program Director, iTHEMS)
Dr. Yuka Kotorii (Visiting Scientist, iTHEMS / Associate Professor, Mathematics Program, Graduate School of Advanced Science and Engineering, Hiroshima University / Visiting Scientist, Mathematical Analysis Team, RIKEN Center for Advanced Intelligence Project (AIP))
Dr. Shigehiro Nagataki (Deputy Program Director, iTHEMS / Chief Scientist, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))
Dr. Makiko Nio (Senior Researcher, RIKEN Nishina Center for Accelerator-Based Science (RNC))
Dr. Ryosuke Iritani (Research Scientist, iTHEMS)
Dr. Ai Niitsu
Dr. Shigenori Otsuka (Research Scientist, iTHEMS / Research Scientist, Data Assimilation Research Team, RIKEN Center for Computational Science (R-CCS))
Dr. Emi Yukawa (Assistant Professor, Department of Physics, Faculty of Science Division I, Tokyo University of Science)

Venue: Changed to Zoom

Event Official Language: Japanese

External Event

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Tetsuo Hatsuda x Koji Hashimoto x Aiko Teranishi "Science for the Future"-"The Usefulness of Useless Knowledge" (University of Tokyo Press) Commemorative Publication

October 10 at 15:00 - 17:00, 2020

Dr. Tetsuo Hatsuda (Program Director, iTHEMS)
Prof. Koji Hashimoto (Professor, Department of physics, Osaka University)
Ms. Aiko Teranishi (President and CEO,

Dr. Tetsuo Hatsuda, iTHEMS Program Director, published "The Usefulness of Useless Knowledge" in this July by the University of Tokyo Press. This book is a collection of essays by Abraham Flexner, the first director of the Institute for Advanced Study in Princeton, USA, and Robbert Dijkgraaf, the current director.

To celebrate the publication of this book, a talk event will be held at Bookstore B&B.

Venue: via Zoom

Event Official Language: Japanese


MCME SYMPOSIUM 2020 thumbnail


October 15 - 16, 2020

Dr. Tetsuo Hatsuda (Program Director, iTHEMS)
Dr. Ryusuke Hamazaki (Senior Research Scientist, iTHEMS / RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team, RIKEN Cluster for Pioneering Research (CPR))

"MCME SYMPOSIUM 2020" will be held at the Musashino Center of Mathematical Engineering of Musashino University. This symposium is free of charge and open to everyone.

[Some excerpts from the program]
Friday, October 16
13:30-14:40 Dr. Ryusuke Hamazaki
14:50-16:00 Dr. Tetsuo Hatsuda

Venue: via Online

Event Official Language: Japanese


iTHEMS Biology Seminar

Bayesian nonparametric estimation of Random Dynamical Systems

October 21 at 14:00 - 15:00, 2020

Dr. Christos Merkatas (Postdoctoral Researcher, Aalto University, Finland)

In this talk, a Bayesian nonparametric framework for the estimation and prediction, from observed time series data, of discretized random dynamical systems is presented [1]. The size of the observed time series can be small and the additive noise may not be Gaussian distributed. We show that as the dynamical noise departs from normality, simple Markov Chain Monte Carlo method (MCMC) models are inefficient. The proposed models assume an unknown error process in the form of a countable mixture of zero mean normals, where a–priori the number of the countable normal components and their variances is unknown. Our method infers the number of unknown components and their variances, i.e., infers the density of the error process directly from the observed data. An extension for the joint estimation and prediction of multiple discrete time random dynamical systems based on multiple time-series observations contaminated by additive dynamical noise is presented [2]. In this case the model assumes an unknown joint error process with a pairwise dependence in the sense that to each pair of unknown dynamical error processes, we assign a– priori an independent Geometric Stick-Breaking process mixture of normals with zero mean. These mixtures a–posteriori will capture common characteristics, if there are any, among the pairs of noise processes. We show numerically that when the unknown error processes share common characteristics, it is possible under suitable prior specification to induce a borrowing of strength relationship among the dynamical error pairs. Then time-series with an inadequate sample size for an independent Bayesian reconstruction can benefit in terms of model estimation accuracy. Finally, possible directions for future research will be discussed.

Venue: via Zoom

Event Official Language: English


Symposium in Commemoration of Professor Emeritus Shun'ichi Amari receiving the Order of Culture

October 21 at 13:00 - 18:00, 2020

A symposium will be held to commemorate Professor Emeritus Shun'ichi Amari (Graduate School of Engineering, The University of Tokyo) receiving the 2019 Order of Culture.

Venue: via Online

Event Official Language: Japanese


iTHEMS Theoretical Physics Seminar

Realistic shell model and chiral three-body force

October 22 at 13:30 - 15:00, 2020

Dr. Tokuro Fukui (Researcher, Yukawa Institute for Theoretical Physics, Kyoto University)

We show an evolution to derive the effective Hamiltonian in the shell-model framework starting from two- and three-body interactions based on the chiral effective field theory. A new way to calculate three-body matrix elements of the chiral interaction with the nonlocal regulator is proposed.

We apply our framework to the p-shell nuclei and perform benchmark calculations to compare our results with those by an ab initio no-core shell-model. We report that our results are satisfactory and the contribution of the three-body force is essential to explain experimental low-lying spectra of the p-shell nuclei. We discuss the contribution of the three-body force on the effective single-particle energy extracted from the monopole interaction.

Next, we investigate the shell evolution on the pf-shell nuclei. We show that the monopole component of the shell-model effective Hamiltonian induced by the three-body force plays an essential role to account for the experimental shell evolution. Moreover, we present our latest results on the investigation of the possible neutron dripline of the Ca isotopes.

Finally, we discuss very neutron-rich systems, namely, the oxygen isotopes at the dripline and beyond, where the interplay between the three-body force and continuum states plays an important role.

Venue: via Zoom

Event Official Language: English

External Event

The Mathematical Society of Japan: Cross-discipline and cross-industry research exchange meeting 2020

October 31 at 10:00 - 17:00, 2020

「数学・数理科学専攻若手研究者のための異分野・異業種研究交流会(研究交流会)」は、 数学・数理科学専攻の博士課程学生をはじめとする若手研究者と産業界を含む異分野の方々 との「双方向の交流の場」として2014年から開催しております。若手研究者の皆様に、諸科学や産業への応用展開のような数学の思わぬ力を発見してもらう ことや、産業界を含む様々な分野で活躍できる場の存在を認識してもらうことが主たる目的 です。高等学校、大学を含む教育・研究機関の教職員や企業関係者の皆様にも、産業界における数学 ・数理科学やその知識を有する人材のニーズを把握してもらうことも目的の一つです。

Venue: via Online

Event Official Language: Japanese

Person of the Week

Prof. Catherine Beauchemin thumbnail

Self-introduction: Catherine Beauchemin


Bonjour! I was already a member of iTHEMS as a Senior Visiting Scientist so probably you already know me. But since September 2020, I became a Deputy Program Director of iTHEMS. I was looking forward to spending more time at RIKEN, working more closely with everyone, but unfortunately, with COVID-19, for now I have to stay in Toronto. As you maybe know, I am a professor of physics, but my research is in the field of virophysics (ヴイルス物理学). I apply the techniques of physics to virology. More generally, I like applying the methods of physics and computational methods to fields where theoretical/quantitative analysis is less common, like biology and health research, or even ergonomics! I think the methodologies developed in physics can translate to many other fields and provide new insights. Most of my work involves/requires direct collaborations with experimental virologists. I also really enjoy convincing other physicists and mathematicians to join in solving these types of problems across disciplines. For me, iTHEMS is an ideal environment to develop such collaborative projects.

In my new role as Deputy Program Director, I want to do my best to help support the young researchers in iTHEMS, and make sure they have everything they need to succeed at their goals. I want to help foster new collaborations, through which everyone can learn new skills, or get help to bring their research to the next level. I have a few ideas that I want to share with all of you over time. If you have some thoughts or concerns, or if you want to discuss something with me, please send me an email anytime. I am happy to get to know you better.

Person of the Week

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Self-introduction: Ken Furukawa


I am Ken Furukawa. My research area is the mathematical theory of partial differential equations related to the fluid dynamics and diffusion phenomena. More specifically, we studied mathematically rigorous justification of the derivation of the primitive equations by the Navier-Stokes equations. The primitive equations have nice properties on well-posedness and have a strong connection with the Navier-Stokes equations. We obtained some results on the well-posedness of the Navier-Stokes equations in this research.

Recently, I have been interested in the mathematical aspect of data assimilation. Data assimilation is very useful to obtain a plausible forecast and is also closely related to our lives. However, mathematically rigorous studies of data assimilation from the mathematical theory of PDE are under development. I will study data assimilation from the view PDE point of view.

Paper of the Week

Week 1 of October


Title: Gabor frames and Wannier bases from groupoid Morita equivalences
Author: Chris Bourne, Bram Mesland

Title: Parity of the neutron consistent with neutron-antineutron oscillations
Author: Kazuo Fujikawa, Anca Tureanu

Title: Wilson-'t Hooft lines as transfer matrices
Author: Kazunobu Maruyoshi, Toshihiro Ota, Junya Yagi

Title: Integer Programming from Quantum Annealing and Open Quantum Systems
Author: Chia Cheng Chang, Chih-Chieh Chen, Christopher Koerber, Travis S. Humble, Jim Ostrowski

Title: Two-nucleon S-wave interactions at the SU(3) flavor-symmetric point with mud≃mphyss: a first lattice QCD calculation with the stochastic Laplacian Heaviside method
Author: Ben Hörz, Dean Howarth, Enrico Rinaldi, Andrew Hanlon, Chia Cheng Chang, Christopher Körber, Evan Berkowitz, John Bulava, M. A. Clark, Wayne Tai Lee, Colin Morningstar, Amy Nicholson, Pavlos Vranas, André Walker-Loud

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