iTHEMS Weekly News Letter

Event Schedule

Events for the 5th week of September 2021


Monday, September 27, 16:00- iTHEMS Colloquium
Friday, October 1, 12:30- Coffee Meeting

Hot Topic

Dr. Tomoki Ozawa thumbnail

Mathematics and Physics: Topology, Insulators and My Research Life


Dr. Tomoki Ozawa (Visiting Scientist, iTHEMS) writes on the website "SURI-JOSHI" about topological insulators and his research life and daily life. Please see the related link for the article.

Research News

Dr. Ryosuke Iritani thumbnail

A New Mechanism to Explain Multispecies Coexistence in Plants - Evolutionary Rescue Caused by the Evolution of Self-Fertilization before Flowering


Koki Katsuhara (Assistant Professor, Okayama University; at the time: Kobe University), Yuuya Tachiki (Assistant Professor, Tokyo Metropolitan University), Ryosuke Iritani (Research Scientist, iTHEMS; at the time: University of California, Berkeley, University of Exeter) and Atsushi Ushimaru (Professor, Kobe University) performed simulations using an individual-based model and found that in two plant species that share the same species of pollinator and are in competition, evolutionary rescue occurs in which the evolution of higher self-fertilization rates in the rarer species results in an increase in population size, thereby promoting long-term coexistence between the two species.

The results of this study add a new theory to explain why multiple flowering species can coexist in the same place, and also provide a new perspective for the evolution of diverse reproductive strategies in plants. Understanding the mechanisms that create and maintain plant diversity, which supports the basis of terrestrial ecosystems, is essential not only for understanding the origin of biodiversity, but also for forming a sustainable society in harmony with ecosystems, and is an important knowledge in both basic and applied aspects.

For more information, please visit the Okayama University website at the related link.

Seminar Report

NEW WG Seminar by Prof. Yuta Murakami on September 15, 2021


Yuta Murakami from Tokyo Institute of Technology told us about "High-harmonic generation in strongly correlated systems." High-harmonic generation (HHG) by strong AC electric fields is one of the hottest topics in cond-mat physics. After a brief overview of HHG in various materials such as gasses and semi-conductors and also recent experimental results in Mott insulators, Yuta explained his recent numerical studies on HHG in strongly correlated systems and clarified unique features of HHG arising from the strongly-correlated nature. About 30 people joined the seminar and we enjoyed fruitful discussions during and after the seminar.

Reported by Hidetoshi Taya

Seminar Report

NEW WG Seminar by Prof. Matteo Baggioli on September 10, 2021


Matteo Baggioli (Jiao-Tong U. Shanghai) gave a talk on "Towards a description of amorphous solids and viscoelastic materials using effective field theory and holographic methods." Amorphous and viscoelastic materials appear in many places, not only in scientific problems but also in our daily life. Despite its ubiquity, there are many intriguing phenomena that are not yet understood, in particular, in the non-linear regime. In the talk, Matteo explained his recent attempts to formulate non-linear responses in amorphous and viscoelastic materials based on holographic and effective-field-theory techniques. Matteo also discussed open problems and future directions that we can pursue in the future. There were about 30 participants from various fields of physics, and we had fruitful discussions from a broad point of view during and even after the talk.

Reported by Hidetoshi Taya

Upcoming Event


iTHEMS Colloquium

Finding Gravitational Waves from the Early Universe

September 27 at 16:00 - 17:30, 2021

Prof. Eiichiro Komatsu (Director, Max Planck Institute for Astrophysics, Germany)

The Cosmic Microwave Background (CMB) gives a photographic image of the Universe when it was still an “infant”. We have been using it to test our ideas about the origin of the Universe. The CMB research told us a remarkable story: the structure we see in our Universe such as galaxies, stars, planets, and eventually ourselves originated from tiny quantum fluctuations in the period of the early Universe called cosmic inflation. While we have accumulated strong evidence for this picture, the extraordinary claim requires extraordinary evidence. The last prediction of inflation that is yet to be confirmed is the existence of primordial gravitational waves whose wavelength can be as big as billions of light years. To this end we have proposed to JAXA a new satellite mission called LiteBIRD, whose primary scientific goal is to find signatures of gravitational waves in the polarisation of the CMB. In this presentation we describe physics of gravitational waves from inflation, and the LiteBIRD proposal.

Venue: via Zoom

Event Official Language: English

Paper of the Week

Week 4, September 2021


Title: On the ease of excitation of black hole ringing: Quantifying the importance of overtones by the excitation factors
Author: Naritaka Oshita

Title: Effective field theory of fluctuating wall in open systems: from a kink in Josephson junction to general domain wall
Author: Keisuke Fujii, Masaru Hongo

Title: Persistence of cluster structure in the ground state of $^{11}$B
Author: Naoyuki Itagaki, Tomoya Naito, Yuichi Hirata

Title: High-dimensional structure learning of sparse vector autoregressive models using fractional marginal pseudo-likelihood
Author: Kimmo Suotsalo, Yingying Xu, Jukka Corander, Johan Pensar
Journal Reference: Stat Comput 31, 73 (2021)

Title: Principal-Axis Analysis of the Eddington Tensor for the Early Post-Bounce Phase of Rotational Core-Collapse Supernovae
Author: Wakana Iwakami, Akira Harada, Hiroki Nagakura, Ryuichiro Akaho, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada

Title: Universal relations between the quasinormal modes of neutron star and tidal deformability
Author: Hajime Sotani, Bharat Kumar

Title: A semi-analytic afterglow with thermal electrons and synchrotron self-Compton emission
Author: Donald C. Warren, Maria Dainotti, Maxim V. Barkov, Bjorn Ahlgren, Hirotaka Ito, Shigehiro Nagataki

Title: Derivative expansion in the HAL QCD method for a separable potential
Author: Sinya Aoki, Koichi Yazaki

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