News

A scientific paper by Mr. Takase, a third-year doctoral student in our laboratory, has been published in the Italian Journal of Cosmology and Astroparticle Physics (JCAP).

The paper proposes an optimal observation method for future satellite observations to validate inflationary models from polarimetric observations of the cosmic microwave background (CMB) radiation, and provides important guidelines for the design of future next-generation CMB polarimetric observation satellites. This research has been introduced in a press release by Okayama University and in Research Highlights.

Ishino Lab. is in charge of systematic error analysis and scan strategy design for LiteBIRD, a CMB polarimetric observation satellite led by the Japan Aerospace Exploration Agency (JAXA).

LiteBIRD is a scientific project that aims to verify inflation, which is believed to have occurred at the birth of the universe, by observing the polarization of the CMB in the entire cosmic sky with high precision. (For details, please see Research Activities)
In order to observe the entire sky of the universe, the satellite will rotate itself at the second Lagrangian point, 1.5 million km away from the earth, to scan the universe (Figure 1).

The key to highly accurate observation of the polarization of the CMB is to suppress systematic errors that originate in the observation equipment. In this study, we found the scan strategy parameters that minimize systematic errors by optimizing the angle and rotation speed of the satellite’s rotation axis.

For more information, please see the following press release/Reserch Highlights article.

Okayama University Press Release
誕生直後の宇宙の姿、衛星観測でどう捉えるか (Japanese)

Research Highlights
How to capture the universe after its birth through space observation (English)

Paper information
Title: Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission
Authors：Y. Takase, L. Vacher, H. Ishino, G. Patanchon, L. Montier et al., LiteBIRD collaboration
DOI: 10.1088/1475-7516/2024/12/036
Link: https://iopscience.iop.org/article/10.1088/1475-7516/2024/12/036

Yusuke visited Kavli IPMU, University of Tokyo to collaborate with Prof. Guillaume Patanchon (ILANCE) on the phylogenetic error of LiteBIRD.

The website of IPMU is here.

Yuya (Ph.D. student) visited IPMU and studied with collaborators.

They worked on a study of how systematic effects caused by asymmetric antenna patterns on satellites change with and without a rotating half-wave plate.

There are still issues to be addressed and we will continue to work on this topic in the future.

From November 25 to 27, Prof. Jo-Yo Ichikura of Nagoya University visited Okayama University to give an intensive lecture and hold a round-table discussion. The lecture was about cosmology and cosmic microwave background radiation, and the discussion session was titled “Measuring Density Fluctuation of the Universe Twice”, which was interesting in that it is possible to test dark energy by CMB observations without assuming uniform isotropy of the Universe.

Yusuke (Ph.D. student) visited the Kavli IPMU, University of Tokyo, to work on the systematic error of LiteBIRD with Prof. Matsumura (Univ. Tokyo) and other CMB researchers at IPMU. Patricia Diego (MPA), who is staying at IPMU, also participated in the discussion and greatly contributed to the study of systematic error theory.

Yusuke is working on a theory for fast estimation and suppression of systematic errors that degrades with CMB polarization observations [Y. Takase et al. 2024, arXiv]. IPMU is responsible for the development of the Polarization Modulator Unit (PMU) on the LiteBIRD low-frequency telescope, which will be used to unify systematic effects originating from the imperfection of the PMU. We discussed with students from Matsumura Lab. an analytical method to treat systematic effects originating from the imperfection of the PMU in a unified manner.

The activity is also introduced in the HP of Kavli IPMU CMB group.

In September, Ms Mami Morinaga from our laboratory completed her Master course.

Simon Madrzyk and Correntin Bourdier (Grenoble INP Phelma, France) have completed their 4-month internship since May. Mami Morinaga, a second-year master’s student, has also completed her master’s thesis after a recent presentation!

Mami authored a master’s thesis in LiteBIRD entitled “Analytical computation of systematic errors of detector gain for CMB full-sky polarization observations”. She conducted research on a method to estimate systematic errors faster than commonly performed time-ordered data analysis by analytically treating systematic errors using advanced mathematics.
She will be employed by a general company in the future, and we look forward to her further success.

Simon and Kiyoshi (2nd year M.S. student) of our lab worked on “Development of Foreground Radiation Removal for CMB Polarization Observation”, and Correntin and Yuya (3rd year Ph.D. student) worked on “Development of High Precision Polarization Light Source” as internship research.

In their final research presentation, they gave a presentation summarizing the results of the four months and deepened the discussion among the lab members. At the end of August, we held a farewell party and had them enjoy Japanese food at an izakaya. We support them both in their future endeavors!

At the request of Prof. Nogami, head of the Department of Physics, Mami Morinaga (2nd year master’s student) who is in our lab wrote an article as a transfer student to Okayama University. The following is a comment from Mami.

I was previously at another private university, but I transferred to Okayama University and gained many valuable experiences.
In particular, I am able to do the cosmology, which I have always wanted to do, here in the Ishino lab.
I hope that those who want to come to Okayama University to study physics (especially those who want to do cosmology) will read this article.

I would like to thank Prof. Nogami, for featuring my transfer experience in this article.

Link to article: Message from a Senior (Mami Morinaga, 2020)

The WPI Site Visit to the International Center for Quantum Field Measurement Systems (QUP) was held on August 5-6, 2024. Ryuji participated in this event as a poster presenter.

In his poster presentation, he gave a detailed explanation of his ongoing research and received valuable comments and advice from many participants. It was a great opportunity to exchange opinions from diverse perspectives and to think about new directions and approaches to research. We intend to use the feedback we received to promote our research in the future.

Okayama University publishes a public relations magazine called “Icho namiki” three times a year, introducing various aspects of Okayama University.

The 106th issue, published in early August 2024, features the activities of Yusuke Takase, a member of our laboratory, and introduces his research and the reason why he decided to pursue a career in universe!
(Click here for the link to Yusuke’s article)

We would like to take this opportunity to thank the writer, photographer, Icho namiki production company, and the University’s PR division for coming to interview him in mid-May, and for their thorough discussions that resulted in a wonderful article. Thank you very much.