iTHEMS Weekly News Letter

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Summary of nuclear astrophysics workshop at Hokkaido University


Nuclear astrophysics workshop was held at Hokkaido University from 6th to 8th of March, 2019, under the support of iTHEMS as well as other institutions and centers. Major issues of this meeting are nuclear data and heavy-element synthesis.
The meeting was very successful with around 60 researchers coming from various fields such as nuclear physics, particle physics, astronomy, astrophysics, astrochemistry, earth and planetary physics. Details of this workshop can be found at their offical web site.

Research News

Dr. Hirotaka Ito thumbnail
Dr. Shigehiro Nagataki thumbnail
Dr. Don Warren thumbnail

Papers soon-to-be published in Nature Communications


A recent paper authored by several iTHEMS members has been accepted for publication in Nature Communications. The authors from iTHEMS include Hirotaka Ito (ABBL /iTHEMS), Shigehiro Nagataki (ABBL/iTHEMS) and Don Warren (iTHEMS). Congratulations! There will be a press release. Here is the explanation on the article by Hirataka Ito:

"The photospheric origin of the Yonetoku relation in gamma-ray bursts” by Hirotaka Ito, Jin Matsumoto, Shigehiro Nagataki, Donald C. Warren, Maxim V. Barkov & Daisuke Yonetoku Accepted for publication in Nature Communications. arXiv:1806.00590

Gamma-ray bursts (GRBs), an intense flash of gamma-rays that is observed almost every day, are the brightest event in the Universe. Decades of studies have revealed that they are originating from a relativistic jet launched at the death of massive star. However, exactly how the gamma-rays are emitted from the jet is still veiled in mystery. One unresolved question is the origin of the correlation between the spectral peak energy and peak luminosity discovered in observations. This “Yonetoku relation” is the tightest correlation found in the properties of GRB emission, providing the best diagnostic for the emission mechanism.

In this study, we focused on the so-called “photospheric emission” model which is one of the leading models for the emission mechanism of GRBs. To test the validity of the model, global dynamics of relativistic jet and radiation transfer must be taken into account. To tackle this issue, we performed three-dimensional relativistic hydrodynamical simulations and radiation transfer calculations to evaluate photospheric emission from relativistic jet that is breaking out of massive star envelope. Our simulations revealed that the Yonetoku relation is reproduced as a natural consequence of the jet-stellar interactions. This result strongly suggests that photospheric emission is the emission mechanism of GRBs.

Upcoming Events


Number Theory Seminar

On special values of the multiple zeta functions of Arakawa-Kaneko type

March 16 at 15:00 - 17:30, 2019

Dr. Yasuo Ohno (Professor, Mathematical Institute, Tohoku University)
Dr. Yuta Suzuki (JSPS Research Fellow, Graduate School of Mathematics, Nagoya University)

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

Event Official Language: English

External Event

Dr. Ade Irma Suriajaya thumbnail

RIKEN Day: Let's Talk with Researchers! "The Wonder of Numbers"

March 17 at 14:00 - 16:00, 2019

Dr. Ade Irma Suriajaya (Special Postdoctoral Researcher, iTHEMS)

In the March RIKEN Day, we will have a talk with Ade Irma Suriajaya, a mathematician who is researching "prime numbers", on the theme of "the wonder of numbers".

See related links for details.

Venue: Science Museum

Event Official Language: Japanese


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Machine Learning for Intelligent Multiscale Modeling of Platelet Dynamics

March 19 at 15:00 - 17:00, 2019

Prof. Yuefan Deng (Professor, Applied Mathematics Department, Stony Brook University, USA)

Venue: 224-226, Main Research Building

Event Official Language: English


iTHEMS Colloquium

ZetaValue2019-iTHEMS Special Mathematics Colloquium

March 21 at 14:00 - 17:30, 2019

Prof. Kohji Matsumoto (Nagoya University)
Prof. Jörn Steuding (University of Würzburg, Germany)

Venue: Okochi Hall, 1F Laser Science Laboratory, RIKEN

Event Official Language: English


Value distribution of zeta and L-functions and related topics thumbnail

Value distribution of zeta and L-functions and related topics

March 22 - 27, 2019

March 22–26, 2019
Main Conference (invited talks, posters and a limited number of short contributed talks)

Welcome Reception: March 22, 2019 (18:00~20:00)
Conference Dinner: March 25, 2019 (18:30~21:00)

March 27, 2019 (9:30~17:00)
One-day Workshop (a series of short contributed talks by young researchers to facilitate active discussions)

Ade Irma Suriajaya (RIKEN)
Yoshinosuke Hirakawa (Keio University)
Masataka Ono (Kyushu University)
Shin-ichiro Seki (Tohoku University)
Keiju Sono (Ehime University)
Shingo Sugiyama (Nihon University)
Yuta Suzuki (Nagoya University)

Tetsuo Hatsuda (RIKEN iTHEMS)
Kenichi Bannai (Keio University, RIKEN AIP Center)

Venue: Okochi Hall, 1F Laser Science Laboratory, RIKEN / Large Meeting Room, 2F Welfare and Conference Building (Cafeteria), RIKEN

Event Official Language: English


Academic-Industrial Innovation Lecture

AI Smart Robot Network

March 22 at 15:00 - 17:00, 2019

Prof. Yoshihiro Ohta (Arithmer Inc. / The University of Tokyo)

Venue: Large Meeting Room, 2F Welfare and Conference Building (Cafeteria), RIKEN

Broadcast: R311, Computational Science Research Building, R-CCS, Kobe Campus, RIKEN

Event Official Language: Japanese


iTHEMS-AIMR Joint Workshop "Medicine meets Mathematics"

March 29 at 10:00 - 17:00, 2019

Takuya Ueda (Tohoku Univ. Hospital)
Noriaki Ogawa (RIKEN iTHEMS)
Takayuki Sakajo (Math. Dep., Kyoto Univ.)
Yoshiki Sugitani (AIMR, Tohoku Univ.)
Jun Seita (RIKEN MIH)
Tetsuro Sekine (Nippon Medical School Hospital)
Masato Taki (RIKEN iTHEMS)
Kenji Takizawa (Faculty of Sci. and Eng., Waseda U.)

Hosted by SUURI-COOL Sendai(iTHEMS-AIMR Mathematical Science Cooperative Lab.)
Co-hosted by iTHEMS, AIMR
Sponsored by CREST "New Challenges for Mathematical Modeling in Clinical Medicine"

Organizers: Hiroshi Suito (AIMR), Tetsuo Hatsuda (iTHEMS)

Venue: 3rd floor Lecture Theater, Katahira Campus, Tohoku University

Event Official Language: Japanese


Tensor Berry connections and their topological invariants

April 2 at 14:00 - 15:00, 2019

Dr. Giandomenico Palumbo (Researcher, Université Libre de Bruxelles, Belgium)

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

Event Official Language: English

Math Lecture

Introduction to Public-Key Cryptography

Introduction to Public-Key Cryptography (10th)

April 9 at 13:30 - 15:30, 2019

Dr. Eren Mehmet Kıral (Visiting Scientist, iTHEMS / Visiting Scientist, Faculty of Science and Technology, Sophia University)

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

Event Official Language: English


AIMR Main Building venue photo

g-RIPS Sendai 2019

June 17 - August 9, 2019

GRIPS (Graduate-level Research in Industrial Projects for Students)-Sendai program was held last summer (June 18 - Aug. 10, 2018) with the support of iTHEMS as well as other institutions and companies. Two industrial projects were launched under the suggestion of TOYOTA and NEC, and two teams composed of US and Japanese students have worked intensively to find solutions of these problems. See for the details of the GRIPS program and the summary of activities at GRIPS-Sendai 2018.

This year, GRIPS-Sendai program will be held from June 17 through Aug. 9, 2019 with a larger scale under the support of iTHEMS. Stay tuned for further information.

Venue: 4F Research Space, AIMR Main Building, Advanced Institute for Materials Research (AIMR), Tohoku University

Event Official Language: English

Featured Paper of the Week

Dr. Yoshimasa Hidaka thumbnail

Diffusive Nambu-Goldstone modes in quantum time-crystals


Symmetry and its breaking is one of the most important notions in modern physics. It is known that when a continuum symmetry is spontaneously broken, there appears a gapless excitation called the Nambu–Goldstone (NG) mode. Such a mode appears in several length scales. In the femtometer scale, pions that are responsible for nuclear force, are the NG modes associated with chiral symmetry breaking. In the meter scale, the sound mode in solid is the NG mode associated with spontaneous breaking of translational symmetry.
In this paper, we study the NG modes associated with spontaneous breaking of the continuous time-translation symmetry in an open quantum system.
For this purpose, we study a system with a van der Pol type nonlinear-friction. By considering small fluctuations around a time-periodic mean-field solution, we find that a gapless collective mode, which is a diffusive one, necessarily appears; this is nothing but the NG mode of a time crystal. We also show that noncommutative breaking of the time-translation and U(1) symmetries results in mixing of the NG modes, and the (typically) propagating NG mode appears.

Tomoya Hayata, Yoshimasa Hidaka
"Diffusive Nambu-Goldstone modes in quantum time-crystals"
arXiv: 1808.07636

Person of the Week

Dr. Ryosuke Iritani thumbnail

Self-introduction: Ryosuke Iritani


Hi, what's up! I'm Ryosuke (Ryo) Iritani. I'm originally from Kobe and did my biology and math undergrad at Kyoto University in Japan. I started my Ph.D. with Yoh Iwasa at Kyushu University in 2011 and worked as a research fellow (DC1) from 2013, visiting Lausanne (Switzerland) and Montpellier (France) to improve my theoretical skills. I then received Ph.D. in 2016 and started my postdoc at the University of California, Berkeley (as a fellow at the University of Exeter, the UK).

I am broadly interested in the field of evolutionary ecology, with a special focus on evolutionary game theory in structured populations. I usually start with my modelings with a motivation to understand ecological phenomena, but I am really keen on developing the general theory of evolutionary ecology. I believe scientific collaboration is the prerequisite to do "good" science, and am therefore always open to collaboration opportunities. My current office is at Kyoto University, so please come talk to me.

I like coffee, soccer, typographical fonts, cooking, math, and living organisms (with a special passion for insects).

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