# Seminar Report

## Biology Seminar on May 27, 2020

2020-06-01

On 27 May, Ayaka Kato, The University of Tokyo, gave a talk at the 6th iTHEMS Biology Seminar. In this seminar, Ayaka talked about the results of the research on mathematical modeling of dopamine-related phenomena. It was not previously known how dopamine is involved in motivation, but in Ayaka's previous studies, the mathematical model from several previous experiments was proposed. In this seminar, Ayaka presented a new model that incorporates learning decay and successfully reproduces the real behavior on a computer simulation based on her new model. Since modeling the relationship between dopamine and motivation is very important both psychologically and medically, I felt that the results of these studies would not only benefit basic research but would also serve as a basis for general-purpose practical science and improve their research motivation.

# Seminar Report

## QFT-core Seminar by Dr. Ryusuke Hamazaki on May 29, 2020

2020-06-01

The second QFT-core seminar entitled “Localization and universality in non-Hermitian many-body systems” given by Dr. Ryusuke Hamazaki (RIKEN Hakubi/iTHEMS) was held on May 29.

Non-Hermitian physics is now one of the topics studied actively, and he is one of the world-leading physicists of this topic. In the seminar, first, he introduced the basic ideas of thermalization of the isolated quantum systems and non-Hermitian physics with simple examples. After that, some cutting-edge progress of non-Hermitian many-body localization, and universality of non-Hermitian random matrices were introduced.

The seminar was held via the Zoom online conference system. Around 20 people participated in the seminar and joined the active discussion.

# Seminar Report

## Math Seminar by Dr. Masaki Taniguchi

2020-05-29

The iTHEMS Math seminar entitled "Knotted 2-spheres in the 4-space and Yang-Mills gauge theory," by Dr. Masaki Taniguchi, was held on 27 May.

In the first part, the speaker reviewed that classical knot theory and history of knot. Especially, he introduced that one and two dimensional knot theory, and gave many examples. For one dimensional knot theory, he explained the fundamental problem of knot theory, i.e., the problem of classifying 1-knots up to equivalent. As an example, he introduced a knot invariant coming from 3-colorings. For two dimensional knot theory, he explained the problem of how we write diagrams of 2-knots in four dimensional Euclidean space. Then he introduced the motion picture.

In the second part, the speaker focuses on a problem considered in differential topology. First, he explained that the fundamental problem in differential topology. Next, he introduced gauge theory and some examples. Finally, as the main result of the talk, he explained his theorem about the difference between continuous and smooth two dimensional knots. He then introduced that the proof uses Yang-Mills gauge theory for 4-manifolds obtained by the surgery of 2-knots.

# Upcoming Events

## Seminar

### The effect of the early kinetic decoupling in a fermionic dark matter model

June 12 at 10:00 - 11:00, 2020

Dr. Tomohiro Abe (Assistant Professor, Division of Theoretical Studies, Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University)

*Detailed information about the seminar refer to the email

Venue: via Zoom

Event Official Language: English

## Special Lecture

### iTHEMS Intensive Course: "Adaptive strategies of organisms, their mathematical bases"

June 18 - 26, 2020

Dr. Yoh Iwasa (Senior Advisor, iTHEMS)

Living systems exhibit features distinct from nonliving physical systems: their structure and behaviors appear to be chosen adaptive. They are the outcomes of evolution. Mathematical formalisms developed in engineering and social sciences (e.g. control theory, game theory, evolutionary game theory) are sometimes very useful in biology.

This course is composed of five sessions (including the colloquium) illustrating the use of different mathematics in modeling particular aspects in biology. [1] Sex expression and sex allocation of marine organisms; [2] Dynamic optimization models for growth and reproduction; [3] Synchronized reproduction of trees (coupled chaotic system); [4] Cancer as a mini-evolutionary process. (colloquium); [5] Evolution of cooperation and illegal logging in tropical forests.

[1] June 18 (Thu) 13:30-15:00

”Sex expression and sex allocation of marine organisms”

keeping gonad of unused sex, dwarf males, environmental sex determination, temperature dependent sex determination in reptiles

[2] June 19 (Fri) 13:30-15:00

"Dynamic optimization models for growth and reproduction“

timing of flowering for annual plants, shoot/root balance, annuals versus perennials, monocarpy (one time reproduction), storage as an insurance, plant defense with alkaloid and age dependence

[3] June 25 (Thu) 13:30-14:30

"Masting, synchronized reproduction of trees: Coupled chaotic system”

masting of trees, coupled chaotic systems, empirical tests, evolution of masting/nonmasting

[4] June 25 (Thu) 15:00-16:30 (Colloquium)

"Cancer as a mini-evolutionary process”

chromosomal instability, acquisition of drug resistance, enhanced cancer risk for companion animals

[5] June 26 (Fri) 13:30-15:00

"Evolution of cooperation”

social evolution by indirect reciprocity, illegal logging in tropical forests and corruption

Venue: via Zoom

Event Official Language: English

## Seminar

### Dark Matter Heating vs. Rotochemical Heating in Old Neutron Stars

June 22 at 16:00 - 17:00, 2020

Prof. Koichi Hamaguchi (Associate professor, School of Science, The University of Tokyo)

*Detailed information about the seminar refer to the email

Venue: via Zoom

Event Official Language: English

# Paper of the Week

## Week 1 of June

2020-06-04

Title: Probing the Universality of Topological Defect Formation in a Quantum Annealer: Kibble-Zurek Mechanism and Beyond

Author: Yuki Bando, Yuki Susa, Hiroki Oshiyama, Naokazu Shibata, Masayuki Ohzeki, Fernando Javier Gómez-Ruiz, Daniel A. Lidar, Adolfo del Campo, Sei Suzuki, Hidetoshi Nishimori

arXiv: http://arxiv.org/abs/2001.11637v3

Title: Effective quantum kinetic theory for spin transport of fermions with collsional effects

Author: Di-Lun Yang, Koichi Hattori, Yoshimasa Hidaka

arXiv: http://arxiv.org/abs/2002.02612v2

Title: Entanglement of Local Operators and the Butterfly Effect

Author: Jonah Kudler-Flam, Masahiro Nozaki, Shinsei Ryu, Mao Tian Tan

arXiv: http://arxiv.org/abs/2005.14243v1

Title: Clustering of conditional mutual information for quantum Gibbs states above a threshold temperature

Author: Tomotaka Kuwahara, Kohtaro Kato, Fernando G. S. L. Brandão

arXiv: http://arxiv.org/abs/1910.09425v2

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