# Seminar Report

## Report on iTHEMS Intensive Course by Dr. Yoh Iwasa - Sex expression and sex allocation of marine organisms

2020-06-19

This month, we hold 4-day intensive course of mathematical biology. This is especially for non-expert. On June 18th, Dr. Yoh Iwasa talked about various mysteries of sex.

For instance, anemonefishes (kumanomi, in Japanese) are male when they are born. As they get bigger, they become female. Interestingly, some coral reef fishes are opposite. As they get bigger, they become male. Why do they show such sex expressions?

Dr. Iwasa astonished us that various mysteries of sex can be resolved from the view point of game theory. According to him, “Anything related to sexual system can be quantified. In terms of the number of offspring, number of reproductive success, and other things. Success of the male depends on whether there are many more males or females. Obviously, this is the game theoretic view point.” During the lecture, the philosophy behind the mathematical modeling was explained in detail.

The lecture on Thursday was attended by more than 160 people through Zoom and Youtube. Dr. Iwasa answered all the uncountable questions from the audience. The wonderful intensive course continues.
- Gen Kurosawa

# Seminar Report

## Math seminar by professor Tasuku Soma

2020-06-23

In 17 June, professor Tasuku Soma (The university of Tokyo) gave a seminar on scaling problem and information geometry at the math seminar.

In the first part he gave an introductory talk on scaling problem. Assume matrix A is given and each entry of A is positive. Matrix scaling problem is to find good matrix L,R with which LAR and (LAR)* has nice property. He then introduced Sinkhorn algorithm. This is an algorithm to calculate "LAR" in the above problem. He then explained operator scaling, which is quantum analogue of matrix scaling.

He explained his recent result on the operator scaling and information geometry. It is known by Csizar that Sinkhorn algorithm for matrix scaling is actually an alternating e-projection, which appears in the information geometry. He then introduced his recent work with Takeru Matsuda. In that work, they proved that operator scaling is also an alternating e-projection.

# Seminar Report

## Dark Matter Working Group Seminar on June 22, 2020

2020-06-25

Astrophysical observations are really important for understanding the nature of dark matter (DM) in multiple aspects. For example, the measurement of the temperature evolution of the neutron star (NS) provides us with new information about the properties of weakly interacting massive particle (WIMP). Since WIMP can interact with nucleon, of which scattering process is intensively searched in direct detection experiments, WIMP in our Universe should be captured by NSs. When the accumulated WIMPs annihilate inside the NS they heat up to modify the temperature evolution of the NS. Such a phenomenon is especially to probe the WIMP in the mass range of mO(100)TeV, i.e., the range where it is difficult to probe with on-Earth experiments.

In order to detect the effect of the WIMP annihilation, one must understand the temperature evolution of the NS in the standard model process accurately. In general, the surface temperature of NS is the highest at their birth, then cools through the photon and neutrino emission. Some of the NS older than ~Myr shows a higher temperature from the simple expectation in the standard model processes and the gap between the observation and the theoretical prediction was believed to be a room for the DM heating.

In the above discussion, the processes of the direct and modified Urca, Bremsstrahlung, and Cooper-pair braking & formation are considered. But another important process so-called the rotochemical heating exists for rotating NSs. The beta equilibrium is not sustained when the NS is rotating and the conversion of the neutron to the proton occurs more frequently than its inverse process. NS heating through this process should be involved when we predict the temperature evolution. The deviation from the beta equilibrium hence the temperature evolution is sensitive to the birth period of the NS.

Based on the calculation involiving a detailed treatment of the NS inner structure, Dr. Hamguchi has shown in this seminar that the rotochemical heating should be more efficient than that from the WIMP annihilation for a typical birth period. There might be no rooms for the WIMP annihilation to heat up the NS. However, the observational estimate of the birth period is still a challenging task, and there could be NSs with high birth periods. Furthermore, the number of such systems that are suitable for testing the WIMP heating scenario will increase in the near future. Such kinds of study should accelerate the collaboration between kinds of experiments to solve the DM mystery.

# Research News

## Neutron star particles go under the LHC microscope

2020-06-25

This article form Symmetry contains an interview with Dr. Tetsuo Hatsuda, Program Director at iTHEMS . Please enjoy.

# Research News

## A Black Hole’s Lunch Provides a Treat for Astronomers

2020-06-25

iTHEMS Senior visiting scientist, Gordon Baym, gave a comment on GW190814 in New York Times.

# Upcoming Events

## Special Lecture

iTHEMS Intensive Course-Evolution of Cooperation

### iTHEMS Intensive Course [5] : "Adaptive strategies of organisms, their mathematical bases" - Evolution of cooperation

June 26 at 13:30 - 15:00, 2020

Prof. 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.

Venue: via Zoom

Event Official Language: English

## Seminar

DMWG Seminar

### DMWG special seminar : “The result of the XENON1T experiment and its implications”

July 22 at 15:30 - 17:00, 2020

Dr. Masaki Yamashita (Associate Professor, Cosmic-ray Research Division, Institute for Space–Earth Environmental Research, Nagoya University)

Venue: via Zoom

Event Official Language: Japanese

# Paper of the Week

## Week 4 of June

2020-06-25

Title: Physical Conditions and Particle Acceleration in the Kiloparsec Jet of Centaurus A
Author: Takahiro Sudoh, Dmitry Khangulyan, Yoshiyuki Inoue
arXiv: http://arxiv.org/abs/2006.12519v1