# Press Release

## Light nucleus predicted to be stable despite having two strange quarks

2020-06-26

Adding an exotic particle known as a Xi hyperon to a helium nucleus with three nucleons could produce a nucleus that is temporarily stable, calculations by RIKEN nuclear physicists have predicted1. This result will help experimentalists search for the nucleus and provide insights into both nuclear physics and the structure of neutron stars.

# Seminar Report

## Biology Seminar by Dr. Shingo Gibo on July 1, 2020

2020-07-02

On 1 July, Shingo Gibo gave a talk at the iTHEMS Biology Seminar. He talked about his research on using mathematical approaches to understand biological oscillations, such as circadian rhythms. His work is a really nice example of the synergy between different disciplines. He draws ideas from mathematics and physics to solve problems in life science, and then his results developed in life science feeds back to various areas related to mathematics and physics. Another highlight of his talk was his cute zoom background :-)

-Jeffrey Fawcett

# Seminar Report

## Math seminar by Dr. Ryusuke Hamazaki on Jun 24, 2020

2020-07-01

The iTHEMS Math seminar entitled "Universal Error Bound for Constrained Quantum Dynamics" by Dr. Ryusuke Hamazaki, was held on 24 Jun.

In the first part, the speaker first introduced two physical examples of constrained dynamics including Rydberg atoms. Then, he explained the motivation of his study: finding quantitative error estimates of constrained-dynamics in generic gapped quantum systems. He introduced his result about a universal and rigorous error bound for a constrained-dynamics approximation in generic gapped quantum systems. Then, he gave the outline of the proof of the error bound. The proof uses the Schrieffer-Wolf transformation (SWT) and Sylvester equation.

In the second talk, he gave a more precise proof of the error bound. In the proof, several computational techniques are used.

# Research News

## "Minute-to-minute weather prediction" article on RIKEN RESEARCH by Takemasa Miyoshi

2020-06-26

Deputy Program Director at iTHEMS Dr. Takemasa Miyoshi talks about weather simulation using a supercomputer "Fugaku".

# Research News

## "Modeling the insides of a neutron star" article on RIKEN RESEARCH about model for the interior structure of neutron stars

2020-06-26

Astrophysicists at RIKEN have developed an improved model for the interior structure of neutron stars. It agrees well with obser-vations, and, unlike previous models, it can be extended to consider what happens when two neutron stars merge.Neutron stars are incred-ibly dense, being the size of a medium asteroid but having masses similar to that of the Sun. They have an onion-like structure, which theorists have been trying to model.

# Announcement

## Dr. Tetsuo Hatsuda supervised a book “The Usefulness of Useless Knowledge" will be released on July 22, 2020

2020-06-29

“The Usefulness of Useless Knowledge" supervised by Dr. Tetsuo Hatsuda, will be released on July 22. Please check on the link for more information.

# Upcoming Events

## Seminar

### Constrained evolution of animal embryogenesis

July 8 at 10:00 - 11:00, 2020

Dr. Yui Uchida (RIKEN Special Postdoctoral Researcher, Laboratory for Multiscale Biosystem Dynamics, RIKEN BDR)

Animals have developed a great variety of morphologies during the course of evolution. Despite this, phylogeny-specific features have sometimes been maintained for hundreds of millions of years, suggesting that there are constraints to morphological evolution. In my talk, I will introduce some of general motivations behind the EvoDevo study and talk particularly about the blank space in morphospaces (Each axis of a morphospace corresponds to a variable describing morphological features). It remains to be seen if these blank areas are caused by impossible developmental pathways. However, computer simulations of embryogenesis, which has been proposed in recent years, may provide a clue to a solution. Finally, I’m going to talk about my research plan based on this.

Venue: via Zoom

Event Official Language: English

## Seminar

### Search for ultralight dark matter with laser interferometric gravitational wave detectors

July 13 at 10:00 - 11:00, 2020

Dr. Yuta Michimura (assistant professor, Department of Physics, The University of Tokyo)

Venue: via Zoom

Event Official Language: English

## Seminar

### Topological data analysis from a practical and mathematical perspective

July 15 at 16:00 - 18:10, 2020

Dr. Yuichi Ike (Researcher, Artificial Intelligence, FUJITSU LABORATORIES LTD.)

1. Topological data analysis and its applications

In this talk, I will explain some methods in topological data analysis (TDA) and their applications. First I recall persistent homology, which is a central tool to analyze the "shape" of a point cloud set. Then I show several applications to material science and time-series analysis. I also talk about our collaborative research with Inria on noise-robust persistent homology and an automated vectorization method of persistence diagrams.

2. Persistence-like distance on sheaf category and displacement energy

In this talk, I will talk about relation among sheaf theory, persistence modules, and symplectic geometry. We introduce a persistence-like distance on Tamarkin sheaf category and prove a stability result with respect to Hamiltonian deformation of sheaves. Based on this result, we propose a new sheaf-theoretic method to give a lower bound of the displacement energy of compact subsets of a cotangent bundle.

This is a joint work with Tomohiro Asano.

Venue: via Zoom

Event Official Language: English

## Seminar

### Human Time vs. Mouse Time in Embryonic Development

July 17 at 16:00 - 17:00, 2020

Dr. Miki Ebisuya (Group Leader, European Molecular Biology Laboratory, Barcelona, Spain)

Different species have different tempos of development: larger animals tend to grow more slowly than smaller animals. My group has been trying to understand the molecular basis of this interspecies difference in developmental time, using the segmentation clock as a model system.

The segmentation clock is the oscillatory gene expressions that regulate the timing of body segment formation during early embryogenesis. We have recently succeeded in recapitulating the segmentation clock from both human and mouse pluripotent stem cells, detecting oscillations and traveling waves in vitro. Interestingly, the oscillation period of human segmentation clock was 5-6 hours while that of mouse was 2-3 hours. Taking advantage of our in vitro system and simple mathematical models, we have been comparing the genome sequences and molecular processes of the segmentation clock between human and mouse to explain the interspecies difference in the oscillation period.

Venue: via Zoom

Event Official Language: English

## 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 1 of July

2020-07-02

Title: Higher-form symmetries and 3-group in axion electrodynamics

Author: Yoshimasa Hidaka, Muneto Nitta, Ryo Yokokura

arXiv: http://arxiv.org/abs/2006.12532v1

Title: Monte-Carlo simulations of fast Newtonian and mildly relativistic shock breakout from a stellar wind

Author: Hirotaka Ito, Amir Levinson, Ehud Nakar

arXiv: http://arxiv.org/abs/2006.14250v1

Title: The classification of symmetry protected topological phases of one-dimensional fermion systems

Author: Chris Bourne, Yoshiko Ogata

arXiv: http://arxiv.org/abs/2006.15232v1

Title: Microscopic theory of the fluctuating hydrodynamics in nonlinear lattices

Author: Keiji Saito, Masaru Hongo, Abhishek Dhar, Shin-ichi Sasa

arXiv: http://arxiv.org/abs/2006.15570v1

Title: Griffiths-McCoy singularity on the diluted Chimera graph: Monte Carlo simulations and experiments on the quantum hardware

Author: Kohji Nishimura, Hidetoshi Nishimori, Helmut G. Katzgraber

arXiv: http://arxiv.org/abs/2006.16219v1

Title: Experimental visually-guided investigation of sub-structures in three-dimensional Turing-like patterns

Author: Martin Skrodzki, Ulrich Reitebuch, Eric Zimmermann

arXiv: http://arxiv.org/abs/2006.16676v1

Title: Stealth dark matter confinement transition and gravitational waves

Author: R. C. Brower, K. Cushman, G. T. Fleming, A. Gasbarro, A. Hasenfratz, X. Y. Jin, G. D. Kribs, E. T. Neil, J. C. Osborn, C. Rebbi, E. Rinaldi, D. Schaich, P. Vranas, O. Witzel

arXiv: http://arxiv.org/abs/2006.16429v1

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