# Press Release

## Tetsuo Hatsuda × Yoshinori Ohsumi × Sayaka Oki Online Discussion: "The Usefulness of 'Useless' Knowledge" will be held on August 22!

2020-08-03

academist, Inc. and RIKEN iTHEMS are pleased to announce the presentation of "Tetsuo Hatsuda x Yoshinori Ohsumi x Sayaka Oki Online Discussion: "The Usefulness of ‘Useless' Knowledge" on Saturday, August 22, 2020 at 1:00 pm.

# Announcement

## “The Usefulness of Useless Knowledge" was published on July 27, 2020

2020-08-06

The Japanese version of "The Usefulness of Useless Knowledge" is now available from the University of Tokyo Press, supervised by iTHEMS Program Director Tetsuo Hatsuda. This book is an essay by Flexner who was a founder of the Institute for Advanced Study, Princeton, and Dijkgraaf who is its current president.

It included with rich translations, researcher's commentary, column articles, and other features, so its made accessible to Japanese readers and is expected to help spread awareness of the importance of basic research. To coincide with the publication of this book, an online discussion on the significance of basic research will be held on August 22. In addition, to help high school students understand the significance of basic research, this book will be donated to designated SSH schools across the country.

# Seminar Report

## Math Seminar by Dr. Tadahiro Miyao

2020-08-05

The iTHEMS Math seminar entitled "Stability of ferromagnetism in many-electron systems”, by Dr. Tadahiro Miyao, was held on 31 July.

In the first part, the speaker reviewed basic properties of electron and introduced the Hubbard model, which describes interacting electrons. In addition, he constructed a model independent framework describing stabilities of ferromagnetism in strongly correlated electron systems. Especially, he reinterpreted the famous Marshall-Lieb-Mattis theorem and Lieb’s theorem. Then he showed that Lieb’s theorem still holds true even if the electron-phonon and electron-photon interactions are taken into account. As examples, he explained the Holstein-Hubbard model and the Kondo lattice model. Finally, he also mentioned other stability classes and open problems.

In the second part, the speaker introduced order preserving operator inequalities and many mathematical tools, such as the Perron-Frobenius-Faris theorem, abstract reflection positivity, the hole-particle transformation, and so on. He also explained how these inequalities are applied to the mathematical study of ferromagnetism. Then Lieb's theorem of the Hubbard model and its stabilities were discussed in terms of the inequalities.

Stability of ferromagnetism in many-electron systems

July 31 at 16:00 - 18:10, 2020

# Seminar Report

## Biology Seminar by Dr. Takashi Okada on July 29, 2020

2020-07-31

On 29th July, Takashi Okada gave us a talk on his work on population genetics theory. He first explained that the classical Wright-Fisher demography cannot inherently consider the realistic situation in which the offspring-number distribution is skewed. Second, he talked about what if we extend the Wright-Fisher demography to a skewed offspring number (power low distribution), showing us that the power-low distribution can dramatically change the timescale of evolution (e.g., sojourn time of fixation of a neutral mutant) as well as large population size limits. We learned that even the classic theory arising from Sewall Wright and Ronald A Fisher entails mathematical expansion. Thank you so much, Takashi, for the great talk!

Time-dependent bias emerges in population models with broad offspring number distributions

July 29 at 10:00 - 11:00, 2020

# Upcoming Events

## Seminar

### Nambu-Goldstone fermion in a Bose-Fermi mixture with an explicitly broken supersymmetry

August 7 at 13:00 - 14:30, 2020

Dr. Hiroyuki Tajima (PhD, Department of Natural Science, Kochi University)

Supersymmetry, which is a symmetry associated with interchange between bosons and fermions, is one of the most important symmetries in high-energy physics but its evidence has never been observed yet. Apart from whether supersymmetric partners such as squark exist or not in our world, it is an interesting problem to explore the consequences of the supersymmetry in an ultracold atomic gas. In this study, we address the Nambu-Goldstone mode called Goldstino associated with the spontaneous supersymmetry breaking in a Bose-Fermi mixture. While the explicit supersymmetry breaking is unavoidable even in cold atomic systems, the energy gap in Goldstino spectra can be measured in such atomic systems. By comparing the energy gaps obtained from the Gell-Mann-Oakes-Renner relation and the random phase approximation, we elucidate how the Goldstino acquires the energy gap due to the explicit breakings. We also show effects of Goldstino pole on the fermionic single-particle spectral functions, which can be measured in the recent experiments.

Venue: via Zoom

Event Official Language: English

## Special Lecture

### Tetsuo Hatsuda × Yoshinori Ohsumi × Sayaka Oki Online Discussion: "The Usefulness of 'Useless' Knowledge" Presented by iTHEMS & academist

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

Dr. Tetsuo Hatsuda (Program Director, iTHEMS)

Prof. Yoshinori Ohsumi (Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology)

Prof. Sayaka Oki (Graduate School of Economics, Department of Socio-Economic System, Nagoya University)

学問の世界で大切なのは、研究者の「なぜ」「不思議だな」という好奇心です。研究者は自らの好奇心をもとに想像力を膨らませ、さまざまな仮説を立て、それを実験、観測、調査で検証し、最終的には理論的に体系づけていきます。このような基礎研究で得られた知識は、私たちの生活に直接「役に立つ」ものではありません。しかし、5年、10年といった期間ではなく、100年、1000年単位で考えると、基礎研究は確実に世の中の役に立ち、私たちはその恩恵にあずかっています。

現在、国内外の大学や研究機関には、企業の経営戦略からきている「選択と集中」の考えが入ってきており、好奇心に基づいた研究を進めることが難しくなっています。令和時代において、私たちはどのように基礎研究を継続させていくことができるのでしょうか。今回のイベントでは、各分野で活躍する3名の研究者にお越しいただき、登壇者の一人でもある初田哲男氏監訳の書籍タイトル『「役に立たない」科学が役に立つ』をテーマとした議論を進めていきます。

Venue: via Zoom

Event Official Language: Japanese

## Lecture

### 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

# Person of the Week

## Self-introduction: Ching-Kai Chiu

2020-08-03

Hello, I will officially join iTHEMS on August 1st as a senior research scientist. My name is Ching-Kai Chiu from Taiwan, and I am a condensed matter physicist. Unfortunately, I cannot enter Japan now due to the travel restriction. Hopefully, I can see everyone in person after COVID-19. Please feel to contact me anytime.

My research interests are topological states of matter, superconductivity, and quantum computing. Specifically, my works are related to topological insulators, semimetals, superconductors, and non-Hermitian systems, as well as the designing of universal quantum computers. I have enjoyed using mathematics to explore condensed matter physics and collaborating with theorists and experimentalists.

However, I don’t want to limit myself in condensed matter physics. I have broad interests in science. When I was in graduate school (the University of Illinois at Urbana-Champaign), I learned general relativity (Sean Caroll’s and Wheeler’s books) and field theory. Recently, I am also interested in (quantum) cryptography and cryptocurrency. It is exciting for me to work in iTHEMS to interact with scientists from different fields.

About my personal life, I lived in many countries, such as USA, Canada, Taiwan, Germany, China. I have enjoyed nature and visited around 20 national parks in the United States. You name it. Yellowstone, Yosemite, and Mount Rainier. My wife and I like to travel. We have been at least 25 countries before COVID-19. My favorite habits are rock climbing and playing board games, such as Terraforming Mars and Power Grids.

# Paper of the Week

## Week 1 of August

2020-08-06

Title: The error term in the Cesàro mean of the prime pair singular series

Author: D. A. Goldston, Ade Irma Suriajaya

arXiv: http://arxiv.org/abs/2007.14616v1

Title: Note on the number of zeros of ζ(k)(s)

Author: Fan Ge, Ade Irma Suriajaya

arXiv: http://arxiv.org/abs/2007.14617v1

Title: Money flow network among firms' accounts in a regional bank of Japan

Author: Yoshi Fujiwara, Hiroyasu Inoue, Takayuki Yamaguchi, Hideaki Aoyama, Takuma Tanaka

arXiv: http://arxiv.org/abs/2007.14630v1

Title: Value-Distribution of the Riemann Zeta-Function along its Julia Lines

Author: Jörn Steuding, Ade Irma Suriajaya

arXiv: http://arxiv.org/abs/2007.14661v1

Title: A singular series average and the zeros of the Riemann zeta-function

Author: D. A. Goldston, Ade Irma Suriajaya

arXiv: http://arxiv.org/abs/2007.16099v1

Title: Blazar Radio and Optical Survey (BROS): A catalog of blazar candidates showing flat radio spectrum and their optical identification in Pan-STARRS1 Surveys

Author: Ryosuke Itoh, Yousuke Utsumi, Yoshiyuki Inoue, Kouji Ohta, Akihiro Doi, Tomoki Morokuma, Koji S. Kawabata, Yasuyuki T. Tanaka

arXiv: http://arxiv.org/abs/2008.00038v1

Title: Avoided crossing in gravitational wave spectra from protoneutron star

Author: Hajime Sotani, Tomoya Takiwaki

arXiv: http://arxiv.org/abs/2008.00419v1

Title: Activity-induced phase transition in a quantum many-body system

Author: Kyosuke Adachi, Kazuaki Takasan, Kyogo Kawaguchi

arXiv: http://arxiv.org/abs/2008.00996v1

Title: Counting Nambu-Goldstone modes of higher-form global symmetries

Author: Yoshimasa Hidaka, Yuji Hirono, Ryo Yokokura

arXiv: http://arxiv.org/abs/2007.15901v1

Title: Illustrations of non-Euclidean geometry in virtual reality

Author: Martin Skrodzki

arXiv: http://arxiv.org/abs/2008.01363v1

Title: Search for dark matter signals towards a selection of recently-detected DES dwarf galaxy satellites of the Milky Way with H.E.S.S

Author: H.E.S.S. Collaboration

arXiv: https://arxiv.org/abs/2008.00688

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