## ◎ Creating the future of humankind by traveling to an unknown world

――What is your area of research?

Kashiwabara: I’m conducting research on the numerical analysis of partial differential equations at the Graduate School of Mathematical Sciences. Partial differential equations are too difficult to solve by human calculations. Therefore, we use computer simulation to approximate solutions through discretization or approximation. Numerical analysis determines if the discretization and approximation processes are mathematically correct. I focus mainly on the partial differential equations of fluids.

Takahashi: I am doing geochemical research in the Graduate Department of Earth and Planetary Science. I analyze the chemical processes that underlie macroscale phenomena we see on earth and in the environment from atomic and molecular scale levels. Every component of the earth is created by chemical reactions. By analyzing the earth’s chemical composition and chemical reaction processes, we can understand how materials were formed and under what environmental circumstances. In short, by using chemistry, we can elucidate the past, present, and future of the earth. This is called “Molecular Geochemistry”.

――What do you like about your research?

Kashiwabara: There are two approaches to numerical analysis. One is a proof-based theoretical approach using pencil and paper while the other is an experimental approach using simulation. This is what’s interesting about this field. It’s like having two weapons to work with — if one approach doesn’t work, we can attack a problem using the other. To put it a bit more broadly, what’s fascinating about science is that you can think about the principles behind things. Mathematics is particularly enjoyable because it allows you rigorously investigate logic.

Takahashi: I find it interesting to approach the macroscopic world of the earth and universe from a microscopic perspective at the atomic and molecular level. You can elucidate various mysteries of the earth’s environment and in the universe by looking at materials.

Researchers are like explorers who are sent by humankind into a dark, unknown world. We explore this mysterious world and then share our discoveries with the public. I think being a researcher and shouldering the future of humankind is quite a romantic profession.

## ◎ Days filled with research while job hunting on the side

――Why did you both choose to study at the Faculty of Science?

Kashiwabara: I fell in love with mathematics while studying for high school entrance exams. I was captivated with the process of deriving solutions by combining various formulas and proving them using logic. I also liked physics, but I was fascinated by mathematics as it requires more rigorous logic. When it was time to decide my major, I thought about entering the Department of Mathematical Engineering and Information Physics in the School of Engineering, which focuses on the application of mathematics to real-world problems; however, I liked the process of mathematical proofs the most, so I entered the Department of Mathematics in the Faculty of Science.

Takahashi: I was originally a chemistry major. When I was a high school student, the ozone hole became a social issue, so I wanted to help tackle these kinds of environmental problems. To accomplish this, I needed to have an understanding of materials, which is why I turned to chemistry. Departments in the Faculty of Science were different at the time, and the Department of Earth and Planetary Science hadn’t yet been established.

――How did you end up on the career path of a researcher?

Kashiwabara: I wasn’t dead set on becoming a mathematician. I simply felt that it would be nice to have a job where I could use mathematics. As I couldn’t picture myself working at a company, I thought I would try the career path of a researcher. My research findings during my time as a postdoc played a large role in this decision.

Takahashi: My father was a researcher so I had a vague idea that I would become one as well. When I was in graduate school, I found research to be incredibly fun. I was immersed in research while students around me were looking for jobs. When I was a second-year master’s student, a paper that I wrote was published in an academic journal, which was exciting because I was able to experience a part of what makes research so exhilarating. However, I didn’t have a specific career path in mind. When I was a third-year doctoral student, I handed in my resume to a research institution, but I wasn’t chosen for the job... Somehow, I ended up being hired to work in the Department of Earth and Planetary Systems Science at Hiroshima University, which was somewhat different from my field at the time. I struggled during that time as well, to be honest. As I had come from a chemistry background, it was quite difficult to remember the names of rocks and minerals. However, diving into a field that straddles chemistry and earth and planetary science when I was young resulted in one of my strengths.

## ◎ If you want to be a researcher, start with science

―― What are your plans for the future?

Kashiwabara: Numerical analysis can be used to collaborate with fields outside of mathematics, such as physics, chemistry, and biology, so I’d like to eventually do projects with researchers in different fields. As a mathematician, I’d also like to contribute to AI (artificial intelligence), which is rapidly spreading throughout society. I believe that AI uses numerical calculation so there’s a possibility to contribute with numerical analysis.

Takahashi: I want to continue to run at the forefront as a researcher. However, it’s not easy to do this for decades on end with only one research theme. The great thing about studying science is that once you have a foundation, you can apply it to various fields. I am working on a wide range of research topics but the foundation for all is chemistry. I am analyzing various objects on earth using chemistry skills I had gained as an undergraduate and graduate student.

Kashiwabara: It’s best to learn the principles and foundations of science while you’re a student. I think it will be difficult to relearn those if you start with application first.

Takahashi: The School of Science is an institution that trains researchers. If you want to become a researcher, then I think you should strengthen yourself at the School of Science so that after you get your degree, you can walk for 40 years at the forefront of your field.

Interview and text: Masatsugu Kayahara (Translation: Kristina Awatsu)

Photography: Junichi Kaizuka

Originally published in The School of Science Brochure 2019