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Alumni Interviews

Where is the value of my research…?

The moment when my worries disappeared

Department of Physics Alumna
Associate Professor, Department of Mathematics, Graduate School of Mathematical Sciences

Chihiro Matsui

April 1, 2021

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When Associate Professor Chihiro Matsui was torn between two paths, music and academia, she chose the latter. Determined to understand all that exists, she proceeded along the path of mathematical physics but encountered hardships. How did she overcome them?

――What kind of research are you doing?

I am doing research in mathematical physics, which is an intermediate area between mathematics and physics. When I studied physics, I was never convinced by experimental results alone. I wanted to find the theories underlying physical phenomena, so I went into this field.

Physical phenomena are known to follow various differential equations but solving these equations is challenging. Mathematical physics is a discipline that replaces physical phenomena with simple models that can be solved using pencil and paper. These models have a beautiful mathematical structure and the same mathematical model can sometimes be found within different physical phenomena.

My research focuses on a one-dimensional magnetic material called a quantum spin chain. In modern physics, microscopic physical phenomena at the atomic and molecular scale are explained by quantum mechanics. When a large quantity of atoms and molecules are gathered together, they display unimaginable behavior that is vastly different from the nature of individual particles. What’s particularly interesting is the phenomenon that occurs on the phase transition point, which is the boundary point between two phases of a substance with different properties. The mathematical structure of the physical model clearly appears in the physical quantities here. The mathematical model of this spin chain model is commonly found in various physical models such as string theory and the traffic model.

――What led you to specialize in this field?

My interest in mathematics started when I was an elementary school student. In junior high school I learned physics and was impressed that the workings of the world can be expressed in mathematics.

When it was time to go to university, I was conflicted about whether to choose piano, which I had been playing since childhood, or academia. Music moves people but it’s a difficult career path to take, so I decided on academia, though I didn’t know how hard it would be at the time. I had a burning ambition to master physics in order to understand everything in the world, which is why I chose to enroll in the Department of Physics in the Faculty of Science.

Hardships were awaiting me when I entered the field of mathematical physics in graduate school. I didn’t know how dry mathematical formulas were related to real life and understanding all that exists. There were also times when I couldn’t see any value in my research.

While I patiently continued to do research, I began to attend many academic conferences. I met various people at these conferences and I remember being surprised and moved that these people with different languages and cultures were interested in researching the same problem as me.

Research is lonely work but we have theories that were laid down by our predecessors, and somewhere in the world there are people facing the same problem as you. There are colleagues who will share your joy when you have a new research finding. When I realized this, I saw the world of mathematical physics, which I had perceived as inorganic, in vivid colors. It felt like solving a mathematics problem.

―― What message do you have for students who are reading this?

Be proactive in going out and seeing the world. If you make connections with people and gain experience, there is no doubt that you will grow.

I would also like to give a message to female students. When I entered the Department of Physics, I was worried about whether there would be other female students. However, I’m truly glad that I didn’t give in to those feelings. There are many opportunities for women in today’s world, so have the courage to follow whatever path you find interesting. There is nothing you can’t do because you’re a woman.

Interview and text: Masatsugu Kayahara (Translation: Office of Communication)
​Photography: Junichi Kaizuka

Originally published in The School of Science Brochure 2018

Chihiro Matsui
Department of Physics Alumna
Associate Professor, Department of Mathematics, Graduate School of Mathematical Sciences
Chihiro Matsui graduated from the Department of Physics in the Faculty of Science, The University of Tokyo, in 2007. She proceeded to obtain her master’s degree in 2009 and doctoral degree in 2012 from the Department of Physics in the Graduate School of Science. She has been an assistant professor in the Graduate School of Information Science and Technology at the University of Tokyo since 2017.
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