[No. 151] Seiichiro Kusuoka

I spent my undergraduate, master's, and doctoral years at Keio University, studying mathematics. Since I was little, I enjoyed games that required logical thinking, like shogi and puzzles, and I was good at mathematics from my junior high and high school days. Therefore, I decided to study mathematics in college, entering Academic Field 2 of the Faculty of Science and Technology and then proceeding to the Department of Mathematics. As an undergraduate, I thought that since I had chosen an environment to study mathematics, I should take it seriously, so I always prepared for and reviewed every one of my math classes. In the Department of Mathematics, there were others who were just as serious about studying math, and I naturally got to know them, including upperclassmen and underclassmen, and we began to study mathematics together. Looking back, I believe I was fortunate to have such peers, which allowed me to learn difficult subjects without feeling it was too much of a struggle.

When it came time to choose a laboratory, I was a bit undecided, but I eventually chose to study probability theory in Professor Yozo Tamura's lab. Professor Tamura set aside separate seminar time for me, giving me the opportunity to learn probability theory within a broad, abstract framework. The content of this seminar was difficult, so preparing for it took a great deal of time. Since I was also participating in seminars with other students in my year, I ended up dedicating almost all my time to mathematics after joining the lab. I have a fond memory of a time when I just couldn't understand the proof of a theorem in the book we were using for the seminar. I searched the library for other books with a proof of the same theorem and spent about two weeks preparing for a single seminar presentation.

And since I had been studying mathematics so seriously, I decided to continue on this path as far as I could, so I advanced to the master's program and then the Ph.D. program. Because I made my decision based purely on the desire to study mathematics, I never had any doubts about my career path. After entering graduate school, I aimed to make a living as a mathematician after graduation, and I went through my student life consciously trying to gain the necessary experience while I was still a student. In particular, I made a conscious effort to look toward the world. During my Ph.D. program, I made sure to attend at least one international research conference each year to interact with foreign mathematicians. At first, I couldn't converse in English, and when I traveled abroad, it was more about experiencing life in a foreign country than learning mathematics. However, thanks to my efforts, I feel I gradually grew as a mathematician. In 2010, I spent six months at the University of Bonn in Germany, where I was able to get used to living and doing mathematics in English. During my stay in Bonn in 2010, I traveled around Europe and gave research presentations in various places. The photo below was taken with Mr. Sakuma, who was in the same year as me in graduate school at Keio University, when we attended a research conference in Dresden, Germany.

Getting a research position at a university is very competitive, but after obtaining my degree and leaving Keio University, I was fortunate enough to work as a postdoc at Kyoto University and an assistant professor at Tohoku University. I am now working as a mathematician with the title of associate professor at Okayama University. I now have my own laboratory and supervise not only undergraduate but also graduate students. My daily work mainly consists of teaching classes and preparing for them, holding seminars with students, and handling university administrative tasks. I spend the rest of my time on research.

My research field has always been probability theory, and within that, I focus particularly on stochastic analysis and its applications to other fields. The work of a university faculty member is much busier than I imagined as a student. Since it's impossible to know how long it will take to get results from research, I always feel like I'm pressed for research time. On the other hand, I became a mathematician because I wanted to do research, so research is also the most enjoyable part of my job. During the summer and spring breaks between semesters, I travel abroad to give research presentations and conduct joint research with foreign mathematicians. Recently, I've been receiving many lecture invitations from overseas, making my days even busier.

Since mathematics is divided into many detailed subfields, I don't often have the chance to meet people whose research areas are far from my own, but I do have opportunities to meet mathematicians who graduated from Keio University. I feel a sense of camaraderie, especially with mathematicians who were students at Keio University around the same time as me, and we enjoy reminiscing about our student days. With those in nearby fields, I also have professional relationships, such as co-authoring papers and collaborating to organize research conferences and seminars. Recently, to coincide with the retirement of my former academic advisor, Professor Yozo Tamura, the alumni organized the Keio Probability Workshop. On that occasion, I also met with lab alumni who had gone on to work in the corporate world, and we talked about what we've been up to. About 10 years have passed since we all graduated, and I learned that everyone is succeeding in their respective paths. I hope to continue to cherish these connections from my student days and devote myself to the world of mathematics.