iTHEMS Weekly News Letter


Ceremony for RIKEN President's Certificates of Appreciation via online


Dr. Y. Kubota, Dr. R. Iritani and Dr. T. Okada received RIKEN President's certificates of appreciation from Dr. Shigeo Koyasu (RIKEN Executive Director) via online on October 22. These certificates are for 2020 Takebe Katahiro Prize for Encouragement of Young Researchers from The Mathematical Society of Japan (Dr. Kubota) and for 15th Young Scientist Award from Japanese Society for Mathematical Biology (Dr. Iritani and Dr. Okada). Many congratulations!

Press Release

Online event "Do you really know what the black hole is?" (iTHEMS x academist)


On December 6, 2020, iTHEMS and academist will have an online event "Do you really know what the black hole is?" Forefront physicists will explain theories and observations of blackholes behind the 2020 Nobel Prize in Physics.

Seminar Report

Biology Seminar by Dr. Takahiro Sakamoto on November 5, 2020


On November 5th, Takahiro Sakamoto from SOKENDAI gave a talk at the iTHEMS Biology Seminar. First, he gave a very nice introduction about the basics of population genetics, and then, he talked about his theoretical study about how genetic divergence proceeds when there is migration between two locally adapted sub-populations. He did very well in explaining his research, which is actually quite complicated, to non-experts, and because of that there were many questions and fruitful discussions. Takahiro is a student from my previous lab and I had in mind to invite him at some point because I knew he is good at giving talks and that his research should be interesting to iTHEMS people. So I was pleasantly surprised that Okada-san invited him, and I was very glad to see that many people enjoyed his talk.

Jeffrey Fawcett

Seminar Report

Biology Seminar by Dr. Jeffrey Fawcett on October 29, 2020


In iTHEMS biology seminar on October 29, Jeffery Fawcett (RIKEN iTHEMS) gave us a talk on genomic data analysis. He started from explaining basic concepts of evolution and explained a couple of important quantities in population genetics, such as nucleotide diversity and the site frequency spectrum, which can be used to infer an underlying evolutionary process from sampled DNA sequences. He also explained statistical methods to study population structures and illustrated one of the methods in a study of the history of Japanese populations, which was very interesting. He made a great effort into his presentation. His talk was very educational and informative, and both experts and non-experts enjoyed his talk. Besides, the next biology seminar on 11/5 was on theoretical population genetics (I was actually the host), and Jeff helped us to prepare for the next week's seminar. Thank you very much, Jeff!
- Takashi Okada

Basics of population genomic data analysis image

Upcoming Events


The 13th MACS Colloquium thumbnail

MACS ColloquiumSupported by iTHEMSSUURI-COOL (Kyoto)

The 13th MACS Colloquium

November 13 at 15:00 - 18:00, 2020

Prof. Shin-ya Kawaguchi (Professor, Division of Biological Sciences, Kyoto University Graduate School of Science)
Dr. Yuji Sugita (Senior Research Scientist, iTHEMS / Chief Scientist, Theoretical Molecular Science Laboratory, RIKEN Cluster for Pioneering Research)

15:00- Talk by Prof. Shin-ya Kawaguchi
16:15- Talk by Dr. Yuji Sugita
17:15- Discussion

Venue: via Zoom

Event Official Language: Japanese


Dr.  thumbnail

iTHEMS Math Seminar

Efficient probabilistic assessment of building performance: sequential Monte Carlo and decomposition methods

November 13 at 16:00 - 18:10, 2020

Dr. Tianfeng Hou (Postdoctoral Researcher, iTHEMS / Postdoctoral Researcher, Prediction Science Laboratory, RIKEN Cluster for Pioneering Research (CPR) / Postdoctoral Researcher, Data Assimilation Research Team, RIKEN Center for Computational Science (R-CCS))

The use of numerical simulations for complex systems is common. However, significant uncertainties may exist for many of the involved variables, and in order to ensure the reliability of our simulation results and the safety of such complex systems, a stochastic approach providing statistics of the probability distribution of the results is of crucial importance. However, when a highly accurate result is required, the conventional Monte Carlo based probabilistic methodology inherently requires many repetitions of the deterministic analysis and in cases where that deterministic simulation is (relatively) time consuming, such probabilistic assessment can easily become computationally intractable. Hence, to reduce the computational expense of such probabilistic assessments as much as possible, the targets of this seminar are twofold: (1), to exploit an efficient sampling strategy to minimize the number of needed simulations of Monte Carlo based probabilistic analysis; (2), to investigate a surrogate model to reduce the computational expense of single deterministic simulation.

This seminar contains two parts and will be accompanied by a set of illustrative building physical case studies (analysis of the heat and moisture transfer through building components). The first part of this seminar focusses on the use of quasi-Monte Carlo based probabilistic assessment for building performance, since it has the potential to outperform the standard Monte Carlo method. More specifically, the quasi-Monte Carlo sampling strategies and related error estimation techniques will be introduced in detail. In addition, questions on under which conditions the quasi-Monte Carlo can outperform the standard Monte Carlo method will be answered by a set of analyses. The second part of this seminar targets the investigation of using model order reduction methods for optimizing the deterministic simulation, given that it generally allows a (large) reduction of the simulation time without losing the dynamic behavior of the conventional models (such as the transient finite element analysis). Particularly, the fundamental concepts of one common model order reduction method – proper orthogonal decomposition (POD) will be provided, and its potential use for simulating (building physical) problems with different levels of non-linearity and complexity will be illustrated.

Venue: via Zoom

Event Official Language: English


iTHEMS Math Seminar

Representations of fundamental groups and 3-manifold topology

November 16 at 16:00 - 18:10, 2020

Dr. Takahiro Kitayama (Associate Professor, Graduate School of Mathematical Sciences, The university of Tokyo)

In 3-dimensional topology the great progress during the last two decades revealed that various properties of 3-manifolds are well understood from their fundamental groups. I will give an introduction to the study of splittings of 3-manifolds along surfaces, with an emphasis on an application of group representations. A fundamental and difficult problem in general is to find surfaces essentially embedded in a given 3-manifold. I will explain how such surfaces are detected by deformations of representations of the fundamental group, and what information of detected surfaces is described in terms of topological invariants derived from representations.

Venue: via Zoom

Event Official Language: English



The Unreasonable Effectiveness of Quantum Theory in Mathematics

November 26 at 10:00 - 11:30, 2020

Prof. Robbert Dijkgraaf (Director, Institute for Advanced Study in Princeton, USA)

November 26 at 10:00-11:30, 2020 (JST)
November 25 at 20:00-21:30, 2020 (EST)

The physical concepts of quantum theory, in particular of quantum gravity and string theory, have proven to be extremely powerful in addressing deep problems in pure mathematics, from knot invariants to algebraic geometry. Is there such a thing as “quantum mathematics”? Should we add Feynman diagrams, strings, branes and black holes to the language of mathematics?

Venue: via Zoom

Event Official Language: English

External Event

Sponsored by academistSupported by RIKEN SUURI CORPORATION

Presented by iTHEMS & academist - Do you really know what the black hole is?

December 6 at 14:00 - 16:00, 2020

Dr. Shigehiro Nagataki (Deputy Program Director, iTHEMS / Chief Scientist, RIKEN Astrophysical Big Bang Laboratory)
Dr. Yoshiyuki Inoue (Senior Visiting Scientist, iTHEMS / Associate Professor, Department of Earth and Space Science, Graduate School of Science, Osaka University)
Dr. Yuki Yokokura (Senior Research Scientist, iTHEMS)

–From the latest theories and observations to the explanation of the Nobel Prize in Physics! An introduction to black holes from active physicists–

The 2020 Nobel Prize in Physics was awarded to Sir Roger Penrose, Prof. Dr. Reinhard Genzel and Prof. Andrea Ghez for their contributions to the theory and observation of black holes. Black holes have continued to provide hot topics in recent years, such as gravitational waves from black hole coalescence and black hole imaging, but do you really know what black holes are? Three cutting-edge black hole researchers will explain its identity and mystery.

Venue: via Online

Event Official Language: Japanese

Paper of the Week

Week 2 of November


Title: The maximal excess charge in reduced Hartree-Fock molecule
Author: Yukimi Goto

Title: The maximum energy of shock-accelerated electrons in a microturbulent magnetic field
Author: Donald C. Warren, Catherine A. A. Beauchemin, Maxim V. Barkov, Shigehiro Nagataki

Title: Quantification of Ebola virus replication kinetics in vitro
Author: Laura E. Liao, Jonathan Carruthers, Sophie J. Smither, CL4 Virology Team, Simon A. Weller, Diane Williamson, Thomas R. Laws, Isabel Garcia-Dorival, Julian Hiscox, Benjamin P. Holder, Catherine A. A. Beauchemin, Alan S. Perelson, Martin Lopez-Garcia, Grant Lythe, John Barr, Carmen Molina-Paris

Title: Self-learning Monte-Carlo for non-abelian gauge theory with dynamical fermions
Author: Yuki Nagai, Akinori Tanaka, Akio Tomiya

Title: Spin-orbital magnetic response of relativistic fermions with band hybridization
Author: Yasufumi Araki, Daiki Suenaga, Kei Suzuki, Shigehiro Yasui

Title: Diabatic quantum annealing by counter-diabatic driving
Author: Luise Prielinger, Andreas Hartmann, Yu Yamashiro, Kohji Nishimura, Wolfgang Lechner, Hidetoshi Nishimori

Title: Estimating the nuclear saturation parameter via low-mass neutron star asteroseismology
Author: Hajime Sotani

Title: From supernova to supernova remnant: comparison of thermonuclear explosion models
Author: Gilles Ferrand, Donald C. Warren, Masaomi Ono, Shigehiro Nagataki, Friedrich K. Roepke, Ivo R. Seitenzahl, Florian Lach, Hiroyoshi Iwasaki, Toshiki Sato

Title: Ab initio construction of the energy density functional for electron systems with the functional-renormalization-group aided density functional theory
Author: Takeru Yokota, Tomoya Naito

Title: Distribution of Energy-Momentum Tensor around a Static Quark in the Deconfined Phase of SU(3) Yang-Mills Theory
Author: Ryosuke Yanagihara, Masakiyo Kitazawa, Masayuki Asakawa, Tetsuo Hatsuda

Title: Wigner functions and quantum kinetic theory of polarized photons
Author: Koichi Hattori, Yoshimasa Hidaka, Naoki Yamamoto, Di-Lun Yang

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