Volume 178

iTHEMS Weekly News Letter

Event Schedule

Events for the 3rd week of December 2021

2021-12-09

Wednesday, December 15, 13:30– 15:00 NEW WG Seminar
Wednesday, December 15, 17:00– 18:00 DMWG Seminar
Friday, December 17, 12:30- Coffee Meeting

Seminar Report

iTHEMS Biology Seminar by Dr. Yuka Suzuki on November 18, 2021

2021-12-07

On November 18, Yuka Suzuki from Okinawa Institute of Science and Technology (OIST) gave a talk titled "Spatial structure in ecology: the effects of dispersal network structure on biodiversity pattern and stability in metacommunities" at the iTHEMS Biology Seminar. She introduced the basic concepts of spatial structure in ecology and explained how computational tools and network theoretical concepts are used to investigate spatial structures in ecology using her own study. Her talk was easy to understand and also very interesting and stimulated many questions and discussions. I believe it was a very worthwhile time for many participants. Thanks Yuka!

Reported by Jeffrey Fawcett

Seminar Report

iTHEMS Math Seminar by Dr. Shinichiro Seki on November 19, 2021

2021-12-07

On November 19, we invited Professor Shin-ichiro Seki from Aoyama Gakuin University to give a talk in the Math Seminar. He explained about the graph removal lemma, which is one of the key ingredients of the proof of his recent joint work with Kai, Mimura, Munemasa and Yoshino on a generalization of the celebrated Green-Tao theorem. In the first half of the talk, he gave a survey of Szemerédi's regularity lemma and the graph removal lemma, and explained how to extend the removal lemma to the case of (weighted) hypergraphs. In the second half of the talk, he presented Fox's result on a quantitative version of the graph removal, and discussed the prospects for future research. After the seminar, we had an online drinking party, and enjoyed a lot of discussion with the speaker.

Reported by Hiroyasu Miyazaki

Seminar Report

NEW WG Seminar by Prof. Ryosuke Oketani on November 25, 2021

2021-12-07

Ryosuke Oketani from Kyushu University gave a talk on "Imaging Theory of Optical Microscopy: Basic to Super Resolution." Optical microscopy is a powerful tool to observe microscopic objects such as living micro-organisms. Recently, several super-resolution techniques have been developed, which enabled us to overcome the limit in spatial resolution caused by the wave nature of light. Ryosuke explained the basics and recent theoretical developments of optical microscopy and the super-resolution techniques. We also had fruitful discussions on the theory of optical microscopy from an interdiciplinary point of view.

Reported by Hidetoshi Taya

Seminar Report

iTHEMS Math Seminar by Prof. Koichi Taira on November 26, 2021

2021-12-07

In November 26, there was a seminar by professor Kouichi Taira. He explained the relations between self-adjointness and the completeness of the classical dynamics. He especially explained a conjecture that self-adjointness and completeness of classical dynamics are equivalent. He then gave some examples on this conjectures.

Reported by Keita Mikami

Seminar Report

iTHEMS Biology Seminar by Prof. Hidetoshi Shimodaira on December 9, 2021

2021-12-10

In this week’s biology seminar, the invited speaker Prof. Hidetoshi Shimodaira introduced his recent work about selective inference. Selective inference is an important statistical problem described also by another word “the file-drawer effect”. For example, Journals are much more likely to publish studies with low P values, and the readers never hear about the great number of studies that showed no effect and were filed way. This makes it difficult to assess the strength of a reported P value. The challenge of correcting for the effects of selection is a complex one. Prof. Hidetoshi Shimodaira explained a method to improve the previously proposed approximately unbiased test by adjusting the selection bias. This method is applied to predict trees and edges in phylogeny. In the seminar, he started by an interesting introduction of Darwin's theory of evolution and the tree of life. Based on this theory, modern phylogenetic inference is developed by analyzing DNA sequences of species as system relationships like trees. He also showed us, different statistical tests can give different P values of trees and edges in the trees. Therefore, we should be careful doing the tests and aware of the bias types in the problem.
We thank Prof. Hidetoshi Shimodaira for his great talk and precious time with us!

Reported by Yingying Xu

Upcoming Events

Seminar

ABBL-iTHEMS Joint Astro Seminar

Magnetic field dependence of neutrino-driven core-collapse supernova models

December 10 (Fri) at 14:00 - 15:00, 2021

Jin Matsumoto (Assistant Professor, Keio Institute of Pure and Applied Sciences (KiPAS), Graduate School of Science and Technology, Keio University)

Massive stars can explode and release huge energy (typically 10^51 erg) at the end of their life. It is one of the most energetic explosions in the Universe and is called a core-collapse supernova. The impact of the magnetic field on the explosion mechanisms of the core-collapse supernova is a long-standing mystery. Recently, we have updated our neutrino-radiation-hydrodynamics supernova code (3DnSNe, Takiwaki et al. 2016) to include magnetohydrodynamics (MHD). Using this code, we have performed three-dimensional MHD simulations for the evolution of non-rotating stellar cores focusing on the difference in the magnetic field of the progenitors. Initially, 20 and 27 solar mass pre-supernova progenitors are threaded by only the poloidal component of the magnetic field, which strength is 10^10 (weak) or 10^12 (strong) G. We find that the neutrino-driven explosion occurs in both the weak and strong magnetic field models. The neutrino heating is the main driver for the explosion in our models, whereas the strong magnetic field slightly supports the explosion. In my talk, I will introduce the details of this mechanism.

Venue: via Zoom

Event Official Language: English

Seminar

NEW WG Seminar

Cosmological particle production as Stokes phenomena

December 15 (Wed) at 13:30 - 15:00, 2021

Yusuke Yamada (JSPS Research Fellowship for Young Scientists, Research Center for the Early Universe (RESCEU), The University of Tokyo)

Particle production from “vacuum” takes place in time-dependent backgrounds. In very early universe, particularly just after inflation, expanding metric as well as oscillating scalar fields play the role of such backgrounds. Mathematically, “particle production from vacuum” can be understood as “Stokes phenomena”, and such understanding enables us to estimate the amount of produced particles in a systematic way. In this talk, I will review the relation between Stokes phenomena and particle production. Then, from the Stokes phenomena viewpoint, I will (re)consider particle production associated with expanding universe, an oscillating scalar field, or both of them. I will also discuss the time evolution of particle number, and its relation to the ambiguity of “vacuum states”.

Venue: via Zoom

Event Official Language: English

Seminar

DMWG Seminar

The FASER experiment

December 15 (Wed) at 17:00 - 18:00, 2021

Hidetoshi Otono (Assistant Professor, Research Center for Advanced Particle Physics, Kyushu University)

FASER, the ForwArd Search ExpeRiment, is an experiment dedicated to searching for light, extremely weakly-interacting particles at the LHC. Such particles may be produced in the LHC’s high-energy collisions and then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. FASER, also includes a sub-detector, FASER$\nu$, designed to detect neutrino’s produced in the LHC collisions and to study their properties. This seminar will describe the physics motivations, detector design, expected performance of FASER, and current status, as well as the physics prospects.

Venue: via Zoom

Event Official Language: English

Paper of the Week

Week 2, December 2021

2021-12-09

Title: Most charming dibaryon near unitarity
Author: Yan Lyu, Hui Tong, Takuya Sugiura, Sinya Aoki, Takumi Doi, Tetsuo Hatsuda, Jie Meng, Takaya Miyamoto
arXiv: http://arxiv.org/abs/2112.01682v1

Title: Information Scrambling Versus Quantum Revival Through the Lens of Operator Entanglement
Author: Kanato Goto, Ali Mollabashi, Masahiro Nozaki, Kotaro Tamaoka, Mao Tian Tan
arXiv: http://arxiv.org/abs/2112.00802v1

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