Monday, May 24, 16:00- Math Seminar
Thursday, May 27, 10:00- iTHEMS Biology Seminar
Friday, May 28, 11:30- Coffee Meeting

On April 22, the iTHEMS Math seminar was held (Sorry for the delay of the report!).
This time, we invited Dr. Iyan Mulia from RIKEN Cluster for Pioneering Research, Prediction Science Laboratory.

The title of the talk was “Alternative tsunami observing and forecasting systems”.
The main topic of the talk was his work about how to catch and predict tsunami.

First, he proposed new approaches to construct tsunami observing systems. There exist various observing systems already, but they share a big problem that they are very expensive. Since observing systems need to be updated regularly, it is very important to reduce the cost. Iyan’s proposal is to make use of existing commercial vessels and airplanes. Since they already exist and form a dense network all over the world, it will suffice to let them observe the sea level altitude and transfer the information. Iyan and his collaborators already demonstrated in experiments that the proposed observing system is accurate enough to detect large tsunamis.
Next, he moved to another topic. Once we observe the occurrence of tsunami, next step is to predict its impact in the areas near the coast. While there are conventional mathematical models which provide very accurate prediction, it needs relatively long time for calculation. This is a non-ignorable defect because it means the delay of the warning to residents. If we use linear models instead of the accurate model, the calculation becomes much faster but the accuracy of the prediction gets low. Iyan’s proposal is plug in the Machine Learning techniques to bridge these two models. He trained neural networks to predict the results of the accurate model from the results of the linear model. This method actually gives a satisfactory result: the prediction is very accurate and fast. If this method is accepted widely, it will be possible to predict the effect of tsunami very accurately in very short time.

Reported by Hiroyasu Miyazaki

Authors: Yuki Yokokura, Jeffrey Fawcett, Takumi Doi and Masato Taki
Editor: Tetsuo Hatsuda and Takashi Tsuboi
Language: Japanese
Release date: May 28, 2021

On April 28, 2021, an online event "Ai Nishida x Tetsuo Hatsuda x Sayaka Oki x Ryosuke Shibato: What We Need to Talk About Now for a Happy Relationship between Researchers and Citizens" was held at B&B, a bookstore in Shimokitazawa. The event was held to celebrate the publication of "The Future of Useless Research," which was released on April 14.
For details, please see the related link.

In iTHEMS Biology Seminar on May 14th, Prof. Yuji Sakai (Univ. of Tokyo) talked about the theoretical model of the autophagosome. First, he explained the autophagosome formation process, where the disk-like and cup-like shapes of the membrane are observed. Then, he talked about the previous theories, where the spontaneous curvature is not considered. Next, he explained his theoretical model, in which the spontaneous curvature is induced and stabilized by the “curvature generator”. By minimizing the free energy in his model, he quantitatively reproduced the autophagosome formation via the disk and the cup. Finally, he mentioned the candidate of the curvature generator.
His attractive talk induced various discussions and questions from the audience. Thank you very much for nice talk, Yuji!

Reported by Hiroshi Yokota

I am a theoretical physicist who works on gravity, cosmology, and quantum field theory. Quantum fluctuations of mater/gravitational fields in an expanding universe or a black hole exhibit thermal radiation and superradiance. These phenomena are important to understand the thermal nature of the gravitational systems and how information of matter is encoded there. Also, the classical linear perturbations of a black hole are characterized by the quasinormal modes of the black hole. This is useful to test classical/quantum gravity theories by the observation of gravitational waves.
Beyond the linear perturbation in gravitational systems, I am also working on non-perturbative phenomena of quantum fields such as vacuum decay in strong gravity. The standard model of particle physics predicts that the Higgs field is metastable, which means that our Universe might eventually undergo a catastrophic vacuum decay and be filled with negative vacuum energy. The vacuum decay process is therefore important to understand the history and fate of the Universe.

Title: Signs of the plastid: Enzymes involved in plastid-localized metabolic pathways in a eugregarine species
Authors: Euki Yazaki, Ryosuke Miyata, Yasuhiko Chikami, Ryo Harada, Takashi Kawakubo, Goro Tanifuji, Takuro Nakayama, Kensuke Yahata, Tetsuo Hashimoto, Yuji Inagaki
Journal Reference: Parasitology International Volume 83, 102364, August (2021)
doi: https://dx.doi.org/10.1016/j.parint.2021.102364

Title: Interstellar Gas Heating by Primordial Black Holes
Authors: Volodymyr Takhistov, Philip Lu, Graciela B. Gelmini, Kohei Hayashi, Yoshiyuki Inoue, Alexander Kusenko
arXiv: http://arxiv.org/abs/2105.06099v1