# Research News

## The modelling work on supernova remnants made at ABBL & iTHEMS is highlighted in the latest image release from NASA's Chandra observatory

2019-10-30

On October 17 the Chandra X-ray Observatory released an updated image of the supernova remnant known as Tycho. Supernova remnants, the aftermath of a stellar explosion, are key to understand how stars end their lives, and how physical elements are synthetized and distributed in the galaxy. The new image, besides being visually striking, contains important clues to understand the explosion physics. Two papers are introduced in the text of the image release. The first paper, Sato et al 2019 (Genus Statistic Applied to the X-ray Remnant of SN 1572: Clues to the Clumpy Ejecta Structure of Type Ia Supernovae), used a new image analysis technique to mathematically characterize the clumpiness of the ejecta. The second paper, Ferrand et al 2019 (From the supernova to the supernova remnant: the three-dimensional imprint of a thermonuclear explosion), presented 3D numerical simulations made from a physically-motivated supernova explosion model. Both works conclude that part of the irregularities visible on the image, at an age of about 450 yr, were actually present from the very beginning. The two teams are now collaborating on the image analysis for the comparison of observations with models. Related work is also on-going with other colleagues at Rikkyo University.

The 3D printed model on the photo was made from G. Ferrand's simulations.

Credit: RIKEN/G. Ferrand, et al & NASA/CXC/SAO/A. Jubett, N. Wolk & K. Arcand

# Seminar Report

## Math Seminar talks by Professor Masaki Tsukamoto

2019-10-30

Professor Masaki Tsukamoto of Kyushu University, the winner of 2019 Geometry Prize of the Mathematical Society of Japan, visited iTHEMS for October 21 - 23 and gave a series of talks at Math Seminar. The theme of his talks was `Mean dimension of dynamical systems and information theory'. On October 21, 15:30-16:30, 16:40-17:40, he gave survey talks at Okochi Hall; In the first part he explained the notion of mean dimension in relation with information theory as an obstruction to embedding dynamical system to the shift on the Hilbert cube. In the second part he explained the notion of mean dimension in relation with data compression and showed that the mean dimension is obtained by applying to a (mini-max) variational principle to the dynamical rate distortion. His talks on October 22 and 23, 13:30-14:30 at the room 435-437 were on the key observation concerning the embedding problem and that on that concerning the dynamical rate distortion, respectively. The participants enjoyed his clear explanations on this mean dimension defined by Gromov which can play important role in the future study of infinite dimensional dynamical systems.

# Upcoming Events

## Seminar

### Some topics in projective geometry of algebraic varieties

November 8 at 16:00 - 18:10, 2019

Dr. Atsushi Ito (Assistant Professor, Nagoya University)

Plan of the seminar: we separate each talk into two. In the first 60 minutes the speaker gives an introductory talk for non-mathematicians. After a short break, the second 60 minutes is spent for a bit more detailed talk for mathematicians (working in other areas). We welcome you joining both parts of the seminar or only the first/second half.

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: English

## Lecture

### RIKEN Open Campus in Kobe

November 9 at 10:00 - 16:30, 2019

Dr. Takumi Doi (Senior Research Scientist, iTHEMS)

RIKEN Open Campus in Kobe will be held on Nov.9, 2019.

Dr. Emiko Hiyama (Kyushu Univ.) and Dr. Takumi Doi (Nishina Center / iTHEMS) will give lectures on computational nuclear and particle physics at Kobe IIB building where SUURI-COOL Kobe is located. Please inform the news to anybody who are interested in visiting RIKEN Kobe.

Venue: Integrated Innovation Building (IIB), Kobe Campus, RIKEN

Event Official Language: Japanese

## Colloquium

### The 10th MACS colloquium

November 15 at 14:45 - 18:45, 2019

Dr. Nami Sakai (Chief Scientist, Star and Planet Formation Laboratory, RIKEN)

Dr. Kazuya Watanabe (Graduate School of Science, Kyoto University)

The 10th MACS colloquium supported by iTHEMS. It will be broadcasted to Wako, but if you can join the colloquium physically in Kyoto, that would be better. iTHEMS provides good confectionery at Kyoto!

Venue: Lecture room #401, Graduate School of Science Building No 6, Kyoto University

Event Official Language: Japanese

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