# Seminar Report

## Math Seminar by Prof. Syuji Yamamoto

2020-01-17

The iTHEMS Math seminar was held on 17 December, inviting Shuji Yamamoto from Keio university. The title of the talk was “Multiple Zeta Values: Interrelation of Series and Integrals”. The topic was multiple zeta values (MZVs), which is a generalization of the values of the Riemann zeta function.

In the first part, the speaker explained the definition of MZVs, and the statement of the Zagier conjecture, which predicts how many algebraic relations should exist among MZVs. Moreover, he explained several known algebraic relations, including Euler relation, Hoffman relation, duality, sum formula, Ohno relation, etc. He also provided two types of proof of duality, one of which is due to himself and Seki.

In the second part, the speaker explained Double Shuffle Relation and Regularization. It is conjectured that these relations generate all the algebraic relations of MZVs, but this is a hard open problem. For example, it is unknown whether the relations imply duality. However, many relations are generated by these relations. The speaker explained some concrete examples, after introducing integral series identity.

# Upcoming Events

## Seminar

### Semiclassical methods in mathematical quantum mechanics

January 23 at 16:00 - 18:10, 2020

Dr. Shu Nakamura (Professor, Gakushuin 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: #435-437, Main Research Building, RIKEN

Event Official Language: English

## Workshop

### Workshop on quantum information science

January 29 at 10:00 - 18:00, 2020

Venue: Suzuki Umetaro Hall, 1F Bioscience Building, RIKEN

Event Official Language: Japanese

## Seminar

### Index of the Wilson-Dirac operator revisited: a discrete version of Dirac operator on a finite lattice

February 25 at 16:00 - 18:10, 2020

Dr. Mikio Furuta (Professor, The University of Tokyo)

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

Event Official Language: English

## Workshop

### [postponed] The 2nd MOST-RIKEN workshop on microscopic approaches to nuclear physics and astrophysics

March 27 - 29, 2020

This workshop is hosted by:

- MOST-RIKEN joint research project on ab initio theory in nuclear physics

- JSPS Grant-in-Aid for Scientific Research (S) “From Quarks to Neutron Stars: Challenges in QCD”

- RIKEN Pioneering Project: Evolution of Matter in the Universe (REMU)

- RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS)

Organizers:

Tetsuo Hatsuda (RIKEN)

Haozhao Liang (RIKEN/The University of Tokyo)

Jie Meng (Peking University)

Shigehiro Nagataki (RIKEN)

Venue: Brain Science Ikenohata Research Bldg. (3rd floor, C56)

Event Official Language: English

# Upcoming Visitors

January 22 - 24, 2020 ## Dr. Hiroyuki FujiKagawa University Visiting Place: Main Research Building |

January 22 - 24, 2020 ## Mr. Koyanagi YukiStudent Trainee, iTHEMS Research fields: Mathematical Biology Visiting Place: Main Research Building |

January 27 - February 3, 2020 ## Dr. Chia Cheng ChangResearch Scientist, iTHEMS Research fields: Particle and Nuclear Physics Visiting Place: ＃233, 2F, Main Research Building |

March 3 - 31, 2020 ## Dr. Gordon BaymSenior Visiting Scientist, iTHEMS Research fields: Quantum Many-body Theory Visiting Place: RIKEN Wako Campus |

# Person of the Week

## Self-introduction: Hajime Sotani

2020-01-16

Understanding neutron star physics is my research topic. Neutron star is provided via supernova explosion, which happens at the last moment of life of massive star. Neutron star is a unique laboratory for understanding the physics in extreme states. In fact, the density inside the neutron star significantly exceeds the nuclear standard density and the magnetic and gravitational fields around/inside the star become much stronger than those observed in our solar system. So, as an inverse problem, one could extract some aspects of physics in such extreme states via the observation of neutron star itself and/or the phenomena associated with neutron stars. For this purpose, (gravitational wave) asteroseismology is a powerful technique, which is similar to seismology in Earth and helioseismology in Sun. With this approach, we are trying to extract the "invisible" neutron star properties. Since our research is not only in astrophysics but also strongly associated with nuclear physics and condensed matter physics, I am very happy if I can make an interdisciplinary collaboration with the members of iTHEMS for solving a problem in neutron stars.

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