# Press Release

## Developed a new theory "Diagrammatic expansion of information flows in stochastic Boolean networks"

2021-02-10

A research collaboration of Dr. Fumito Mori (Assistant Professor, Education and Research Center for Mathematical and Data Science/Faculty of Design, Kyushu University) and Dr. Takashi Okada (Senior Research Scientist, RIKEN iTHEMS) has developed a new theory for "Diagrammatic expansion of information flows in stochastic Boolean networks".

# Research News

## RIKEN NEWS: Tracking the Evolution of Matter in the Universe — From nuclei to atoms and molecules

2021-02-08

A five-year project titled "Material Evolution in the Universe — Nuclei, Atoms, Molecules, and Beyond" is underway at RIKEN starting in 2019. The project is led by the Dr. Sakai at Star and Planet Formation Laboratory, the Dr. Tamagawa at High Energy Astrophysics Laboratory, and the Dr. Nagataki at Astrophysical Big Bang Laboratory, and brings together researchers from inside and outside RIKEN. The goal is to realize a new type of space research that integrates physics and chemistry, and to understand the evolution of matter from nuclei to atoms to molecules.

# Seminar Report

## iTHEMS Theoretical Physics Seminar by Dr. Di-Lun Yang on February 4, 2021

2021-02-05

On February 4, the iTHEMS-phys seminar entitled "Quantum kinetic theory for chiral and spin transport in relativistic heavy ion collisions and core-collapse supernovae" given by Dr. Di-Lun Yang (Keio U.) was held. He has been working for the quantum kinetic theory. In his seminar, first, he introduced the general background of the quantum transport of the massless fermions and its anomaly. Then, he showed its application to the relativistic heavy-ion collisions and core-collapse supernovae.

The seminar was held via the Zoom online conference systems. More than 20 people, including outside from iTHEMS, attended the seminar. The discussion was quite lively, and it was continued for long, even after the seminar.

Quantum kinetic theory for chiral and spin transport in relativistic heavy ion collisions and core-collapse supernovae

February 4 at 13:00 - 14:30, 2021

# Seminar Report

## Biology Seminar by Mr. Yoshifumi Asakura on February 4, 2021

2021-02-05

In iTHEMS Biology Seminar on Feb. 4th, Yoshifumi Asakura (Kyoto University) talked about modeling of the mechano-chemical dynamics of an epithelial sheet. He first reviewed experimental observation of the epithelial sheet dynamics with ERK signals and simple theoretical modeling of the mechano-chemical dynamics. He then presented the main questions, stressing the importance of two-dimensionality and parameter heterogeneity in tissue dynamics. In the method part, he introduced the hierarchical modeling which connects the particle-based and continuum models with the cell tracking data. He showed that the models can reproduce the essential features of the tissue dynamics with ERK signals, and moreover, can be used for the quantitative prediction of the velocity field of cells. His presentation contained many beautiful movies of the epithelial sheet dynamics and model simulations. We are thankful to him for the nice talk!

Kyosuke Adachi

System identification of mechano-chemical epithelial sheet dynamics

February 4 at 10:00 - 11:00, 2021

# Upcoming Events

## Seminar

### Quantum mechanical description of energy dissipation and application to heavy-ion fusion reactions

February 16 at 13:00 - 14:30, 2021

Mr. Masaaki Tokieda (Graduate students, Department of Physics, Tohoku University)

For theoretical description of heavy-ion fusion reactions, two different models have been used depending on the incident energy. At energies above the Coulomb barrier, importance of energy dissipation and fluctuation has been deduced from scattering experiments. To describe them phenomenologically, the classical Langevin equation has successfully been applied. At energies below the Coulomb barrier, on the other hand, the quantum coupled-channels method with a few number of internal states has been applied, and it has succeeded in explaining sub-barrier fusion reactions. While each method succeeds in each energy range, a unified description of heavy-ion fusion reactions from sub-barrier energies to above barrier energies is still missing. To achieve this, we need to treat dissipation and fluctuation quantum mechanically.

In order to describe dissipation and fluctuation quantum mechanically, we have applied ideas of open quantum systems to heavy-ion fusion reactions. I will talk about recent development in this talk. First I will introduce a model Hamiltonian to treat dissipation and fluctuation quantum mechanically, and explain its character and a strategy for numerical studies. I will then apply the model to a fusion problem, and discuss a role of energy dissipation during quantum tunneling. Finally I will discuss a possible future direction for a unified description of heavy-ion fusion reactions.

Venue: via Zoom

Event Official Language: English

## Seminar

### Mapping the Milky Way by VLBI Astrometry

February 16 at 13:30 - 15:00, 2021

Dr. Nobuyuki Sakai (Korea Astronomy and Space Science Institute (KASI), Republic of Korea)

Astrometry is the only way to obtain 6D (position-velocity) phase space information for astronomical objects. The unique capability allows us to examine the past, present, and future of the Milky Way.

Firstly, I will introduce history and basics of astrometry. Secondly, I will overview astrometric projects in the world. Thirdly, I will highlight recent astrometric results about the Galactic structure. Lastly, I will introduce astrometric research in Korea as well as future astrometric projects and sciences in 2020s and 30s.

Venue: via Zoom

Event Official Language: English

## Conference

### Blockchain in Kyoto 2021

February 17 - 18, 2021

Language: Some parts will be in Japanese.

The International Conference on Blockchains and their Applications aims at bringing together researchers and practitioners from various communities of science and technology working on areas related to FinTech, Crypto-asset, and Blockchain.

Venue: partly online

Event Official Language: English

## Seminar

### Journal Club: Large deviation statistics of Markovian quantum systems

February 17 at 13:00 - 14:30, 2021

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))

Large deviation is a mathematical framework to treat “rare events” in random processes [1]. In this journal club, I talk about recent development of large deviation analysis in open Markovian quantum systems [2,3]. I first introduce the notion of large deviation statistics using the simple independent and identically distributed random variables. I then review recent development of level 2.5 large deviation statistics for classical Markovian jump processes and its application to thermodynamic uncertainty relation [4]. Finally, I discuss how the classical results are extended to quantum regime.

Venue: via Zoom

Event Official Language: English

## Colloquium

### The 14th MACS Colloquium

February 17 at 15:00 - 17:30, 2021

Prof. Yoshihiro Kaneko (Associate Professor, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University)

15:00- Talk by Prof. Yoshihiro Kaneko

16:05- MACS Report Meeting FY2019

16:30- Discussion of each study group

Venue: via Zoom

Event Official Language: Japanese

## Seminar

### The Evolution of Primordial Neutrino Helicities under Gravitational and Magnetic Fields and Implications for their Detection

February 22 at 10:00 - 11:30, 2021

Prof. Gordon Baym (Senior Visiting Scientist, iTHEMS / Professor Emeritus, University of Illinois, USA)

Feb.22 (Mon) 10:00am-11:30am (JST)

Primordial neutrinos decoupled in the early universe in helicity eigenstates. As I will discuss, two effects -- dependent on neutrinos having a non-zero mass -- can modify their helicities as they propagate through the cosmos. First, finite mass neutrinos have a magnetic moment and thus their spins, but not their momenta, precess in cosmic and galactic magnetic fields. The second is the propagation of neutrinos past cosmic matter density fluctuations, which bend their momenta, and bend their spins by a smaller amount. (The latter is a general relativistic effect.) Both effects turn a fraction of left-handed neutrinos into right-handed neutrinos, and right-handed antineutrinos into left-handed. If neutrino magnetic moments approach that suggested by the XENON1T experiment as a possible explanation of their excess of low energy electron events -- a value well beyond the moment predicted by the standard model -- helicities of relic Dirac (but not Majorana) neutrinos could be considerably randomized. I finally will discuss the implications of neutrino helicity rotation, as well as their Dirac vs. Majorana nature, on their detection rates via the Inverse Tritium Beta Decay reaction.

Venue: via Online

Event Official Language: English

# Paper of the Week

## Week 2 of February

2021-02-10

Title: Quiescent luminosities of accreting neutron stars with different equation of states

Author: Helei Liu, Akira Dohi, Masa-aki Hashimoto, Yasuhide Matsuo, Guo-Liang Lü, Tsuneo Noda

arXiv: http://arxiv.org/abs/2102.04012v1

Title: An adjunction inequality for the Bauer Furuta type invariants, with applications to sliceness and 4-manifold topology

Author: Nobuo Iida, Anubhav Mukherjee, Masaki Taniguchi

arXiv: http://arxiv.org/abs/2102.02076v1

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