The precise understanding of the local DM density, as well as its velocity distribution, is critical for dark matter (DM) search, especially for direct detection experiments. We need information about the global structure such as the position and rotation velocity of the Solar system when evaluating these quantities. Astrometry, which is a technique to measure the time dependence of the position of stars, powerfully probes the 3D gravitational structure of our Galaxy.

There are two types of astrometric observations: the first one is based on optical (and infrared) photometry. The parallax is obtained by comparing two snapshots of the sky between two epochs. The Gaia mission is the representative for this kind of observation. Gaia reveals the structure of our Galaxy up to ~5kpc from the Sun. The mission is planned to continue the observation to extend our reach to ~10kpc, meaning that it should cover the Galactic Center in the near future. The second one is the VLBI observation. VLBI is an abbreviation of the very-long baseline interferometry. The spatial resolution of milli-arcsecond is achieved with VLBI techniques. However, the sensitivity is limited and long-lasting observations are required in general. In this sense, VLBI and optical photometry are complemental.

One important discovery for DM search from VLBI astrometry is reported in this seminar. The VLBI observation of the Galactic disk region reveals the position of the Sun is closer to the Galactic Center compared to the conventional values used for a long time, and the rotation velocity is higher. This means that our Galaxy is heavier, i.e. contains much DM, and the relative velocity between DM particle and us is different, compared with the previous estimates. Also, the disk region does not reach the equilibrium yet. These facts should change the picture of our Galactic DM structure.

New facilities for astrometric observations are now being planned and constructed. There are diverse possibilities for the synergy between DM search. The astrometry should give important indications such as the merger history of DM halo, dynamical interaction between the Milky Way and its satellite galaxies, the global structure of the Milky Way, and far more. We should stay tuned!

On February 16, the iTHEMS-phys seminar entitled "Quantum mechanical description of energy dissipation and application to heavy-ion fusion reactions" given by Mr. Masaaki Tokieda (Tohoku U.) was held. He introduced his work during graduate school, that is, considering dissipation and fluctuation to the quantum mechanics to unify the description of above the Coulomb barrier and sub-barrier reactions. He also applied the method to heavy-ion fusion reactions.

The seminar was held via the Zoom online conference systems. More than 20 people, including outside from iTHEMS, attended the seminar. The discussion was quite lively, and it was continued for long, even after the seminar.

In iTHEMS biology seminar on February 12, Keitaro Kume (Univ. of Tsukuba) gave us a talk about applying machine learning to the analysis of non-model organisms that are difficult to experiment with. First, Dr Kume introduced us about the brief mitochondrial evolution and several eukaryotes possessed not typical mitochondria as like Mitochondrion related organelle (MRO) which is highly degraded mitochondria. Next, he described the detection of mitochondrial localization signals and their applications, explaining that it is difficult to detect localization signals in mitochondria of non-model organisms, especially MROs. Finally, He obtained a large amount of data on MRO-localized proteins in non-model organisms, and through machine learning using the data as training data, he created a detector that can detect MRO-localized signals in such non-model organisms. He presented a good example of the connection between biological evolutionary research and machine learning, which led to a lively discussion at the seminar. Thank you very much, Kei!