# Hot Topic

## Two conferences at Berkeley - Berkeley Report from Dr. K.Mikami

2019-10-24

MSRI holds a semester program “Microlocal Analysis” in fall 2019. I fortunately attend this program while my stay at University California Berkeley (UCB) via iTHEMS-UCB math young visiting scholar program. There were two conferences on microlocal analysis in the third week of October.

From October 14 to 18, there was a conference entitled “Recent Development in Microlocal Analysis”. It consists of 18 talks on various kinds of topics on microlocal analysis by specialists from all over the world. They contain some topics which is very closely related to my research works, such as observability and semiclassical measure.

In October 19 and 20, there was a conference entitled “Microlocal Analysis and Spectral Theory: A Conference in Honor of Richard Melrose”. Richard Burt Melrose is an Australian mathematician who is famous for his broad research on microlocal analysis and geometry. The speakers include two fields medalists, Terence Tao and Akshay Venkatesh.

Over all, there were around 30 talks(!) in a single week. Though it was a bit tight schedule, all talks were really nice and inspiring. Lastly, it was my great honor to attend these great conferences.

# Hot Topic

## KUIAS-Heidelberg-iTHEMS joint WS was held at SUURI-COOL Kyoto

2019-10-25

KUIAS-Heidelberg-iTHEMS joint WS "Mathematical Sciences and Medicine" was held at SUURI-COOL Kyoto on Oct. 10, 2019 with Motomu Tanaka (Heidelberg/KUIAS) and Tetsuo Hatsuda (iTHEMS) as organizers. The main aim of this workshop was to exchange ideas to create new paradigm in clinical medicine with the help of physicists, mathematicians and biologists. After the welcome address by Shigefumi Mori (Director General of KUIAS, Kyoto Univ. and Science Advisor of iTHEMS), there were 10 talks by the physicists, mathematicians and biologists from Heidelberg Univ., Kyoto Univ., Doshisha Univ. and RIKEN. Each talk was very stimulating and created lively discussions under relaxed atmosphere of SUURI-COOL Kyoto Office. To continue the discussions, we decided to have another meeting in the near future with active participation of medical doctors in Kyoto and Heidelberg.

KUIAS-Heidelberg-RIKEN iTHEMS joint WS "Mathematical Sciences and Medicine"

October 10 at 10:30 - 18:00, 2019

# Seminar Report

## DMWG Seminar by Dr. Toyokazu Sekiguchi

2019-10-24

The 2nd DMWG seminar was held on Oct.21, inviting Dr. Sekiguchi from The Univ. of Tokyo/KEK. Focusing on the weakly interacting massive particle (WIMP) case, he lectured the formation of the minimum mass DM halo in the early Universe and its implications.

WIMP is one of the strongest candidates for DM. From a theoretical point of view, neutral wino in the split-SUSY scenario is an example. One important feature of WIMP is that it achieves the current DM density, usually referred to as the relic abundance, via the so-called freeze-out mechanism. In the early Universe, the thermal equilibrium between WIMPs and the standard model (SM) particles is maintained. As the Universe expands, the temperature decreases then the WIMP annihilation rate to the SM particles becomes smaller than the expansion rate of the Universe. At this point, the number density of DM is fixed. This is the thermal freeze-out mechanism to determine the DM relic density. However, the WIMP and the SM particle are still kinetically coupled even after the thermal freeze-out. In this stage, they transfer momentum by each other through the direct scattering. By carefully calculate the epoch of the kinetic decoupling, the minimum halo mass, which is important in characterizing the DM halo properties and the observable signatures, are determined. He showed that the minimum halo mass should be of the order of O(1e-7) solar mass when we consider the neutral wino in the split SUSY scenario. This value is smaller than that expected when we neglect the kinetic decoupling effect. Furthermore, the total number of small-scale halos resides in the larger halo increases. The enhancement in the number of small-scale halos leads to a higher flux for gamma-ray annihilations in present-day halos. We have an increased possibility of detecting DM signatures in the on-going and planned astrophysical observations.

# Upcoming Events

## Seminar

### Semiclassical defect measures and observability estimate for Schrödinger operators with homogeneous potentials of order zero

October 30 at 8:40 - 10:00, 2019

Dr. Keita Mikami (Research Scientist, iTHEMS)

Seminar will be held from 15:40 to 17:00 on Oct.29(PDT, the U.S. Pacific Daylight Time) as a Harmonic Analysis and Differential Equations Seminar.

Venue: UC Berkeley

Event Official Language: English

## 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

# Upcoming Visitors

October 21 - 23, 2019 ## Dr. Masaki TsukamotoProfessor, Kyushu University Visiting Place: RIKEN Wako Campus |

October 23 - 25, 2019 ## Dr. Christopher BourneVisiting Scientist (Academia), iTHEMS Research fields: Mathematics, Operator Algebras, Topological Phases Visiting Place: ＃233, 2F, Main Research Building |

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