Exchange program at the University of California, San Diego

by Tamon Suehiro

>What this is

My final report about the exchange program at the University of California, San Diego (UC San Diego).

>Who I am

I am a senior at UTokyo, majoring in aerospace engineering and specializing in electric propulsion called Hall Thruster. Despite my major, I have an interest in mathematical physics.

>Academic life

In my first semester, I focused primarily on space engineering courses, while also taking physics and mathematics classes. The teaching style here is quite different from that at Tokyo University, with each subject being taught several times a week, which leads to a much faster pace of learning. Additionally, the assignments were frequent and often challenging, especially in physics and mathematics, where I had to apply theoretical knowledge to solve complex problems. Despite the intensity, I found the space engineering assignments generally more manageable, thanks to my previous experience in the field.

The tasks mainly tested my ability to apply knowledge in a practical way rather than the ability to understand theories and principles. The challenge was primarily the time required to complete them. Overall, the semester helped me refine my problem-solving abilities, giving me a deeper appreciation for both the engineering and theoretical aspects of my studies.

Since the winter semester, I have not been able to enroll in most of the aerospace-related courses, especially the labs and practical courses due to limited class capacity. Even after directly negotiating with the professors, it was still impossible to register for these courses, which was very disappointing. Additionally, since I had already studied abroad during my fourth year of undergraduate studies and had taken many aerospace engineering courses at the University of Tokyo, I decided to give up on taking more engineering courses. Instead, I took this opportunity to revisit and study physics and mathematics once again.

These are the courses I took in the winter and spring semesters.

1. Quantum Field Theory 2: Renormalization and 1-loop calculation

2. Quantum Field Theory 3: Advanced things, like spontaneous symmetry breaking, gauge field, topology, and anomalies.

3. General Relativity 2: Post Newtonian approx., gravitational wave and differential geometry 

4. General Relativity 3: Symmetries in GR, Singularity theorem, and black holes

5. The Mathematics of Finance: Mathematical theory of trading stocks, bonds, currency, and mortgages.

6. Flight Simulation Techniques: Implementation of the motion simulation of the atmospheric flight vehicles.

In the QFT3 course, I had the opportunity to give a lecture-style presentation on a topic of interest. I chose to focus on “Calculation of Anomaly by Fujikawa’s Method,” a subject that formulates an important aspect of quantum field theory called quantum anomalies and calculate them.

Fig. 1. The picture of the whiteboard of the QFT class.

>Extra-Curricular Activities

At UCSD, I had the opportunity to organize and participate in a self-directed mathematics study group with several math students I met during my time there. The format of the seminar was informal yet structured: we would gather regularly and choose one member to present on a topic, either on a rotating basis or with a designated speaker for each session. Each presentation followed a lecture-style format, where the presenter would explain the topic in depth while the rest of us engaged with questions and discussions.

The subjects we chose to explore were very abstract, covering Galois theory, differential geometry, and category theory. These topics were selected not only because they are fundamental in higher mathematics, but also because they presented us with intellectual challenges that pushed our understanding to new levels.

Initially, my motivation for joining and co-leading this seminar was purely driven by a personal interest in mathematics. I have always been fascinated by the elegance and complexity of mathematical structures, and I saw this as a chance to deepen my knowledge alongside like-minded peers. However, as I progressed in my studies—particularly in physics—I began to recognize the profound connections between these abstract mathematical concepts and physical theories.

Realizing the connections between mathematics and physics broadened my understanding of both fields and accelerated my enthusiasm for them. This experience has become a defining part of my academic journey, motivating me to further explore the intersections of physics and mathematics.

Fig. 2. Self-directed mathematics study on Galois Theory.

>Life at UC San Diego

– Sport

I participated in judo practice at UCSD Recreation, and in addition, I attended a dojo(道場) in the suburbs of San Diego. I have been practicing judo for about ten years, throughout middle school, high school, and college. Being able to continue this practice in a foreign country has been a fantastic experience. As you may know, judo is a traditional Japanese martial art, and it’s impressive to see how it has spread and gained popularity in the United States. When I make friends through Japanese martial arts, it’s a moment when I feel glad that I continued with judo. It has not only provided me with physical training but has also allowed me to connect with others and share a piece of my culture, reinforcing the value of my judo journey.

Fig. 3. Photo after Judo practice.

– Food

As mentioned in my interim report, San Diego is home to a wealth of delicious food. Because San Diego is near Mexico, tacos and burritos are so good. Tacos el Gordo my “Numero Uno” of my life!! Here are my best foods.

Fig. 4. Tacos at Tacos el Gordo, Ramen Nagi, and American Diner with my friends.

– Travel

During spring break, I had the opportunity to visit Washington, DC, and New York City. While San Diego is a big city, these two cities are truly in a class of their own. Washington, DC, being the capital of the United States, is rich in history and politics, while New York City stands out as a global financial and cultural center. My time there was incredibly rewarding.

Whenever I travel to a new city, I make it a point to visit museums, however, there were so many museums to explore that I couldn’t possibly see them all during my visit. I found myself wishing I had stayed a bit longer to take more time to expose myself to the great arts. This is one of the highlights of my trip.

Fig. 5. Saying Hello to the statue of Prof. Albert Einstein in DC.

>Challenge living in the US (as an international student)

For me, the biggest challenge of living in America is food. There are three meals a day, and if I skip it, I do not have enough energy. In other words, it is the center of my life. However, the university’s dining plan for on-campus residents is expensive and the food doesn’t taste very good. In addition, if you live abroad for a long time, you start to miss the taste of Japan. So, I went to a local Asian supermarket and bought a set of Japanese seasonings. If you are to study abroad, you should learn how to cook Japanese meals!!

Additionally, something surprising happened: my bicycle’s front wheel was stolen! I had never experienced anything like this in Japan. While I’m not sure if it’s a security issue, it’s perplexing that only the front wheel was taken. Even more astonishing was the sight of many bicycles without front wheels on campus. This clearly indicates a high demand for front wheels within the campus community. I had bought my bicycle used for $80, but replacing just the front wheel would cost me $60. It made me reflect on how business works in such situations—there’s clearly a market for these parts, and people are willing to pay for them. This was why I chose not to buy the front wheel.

Fig. 5. The bicycle its front wheel was stolen.

There was also something that happened to me that was disappointing; At the beginning of the winter semester, I received a research job offer from the company via the professor who taught the propulsion course in the fall semester. Unfortunately, and disappointedly, due to my nationality and visa, it could not be realized. This, plus other subtle reasons such as the rejection to enroll in the engineering courses and my enthusiasm toward physics, were why I changed my major from aerospace engineering to physics.

>My Career Path

I have decided to pursue physics, especially mathematical physics, and I took the entrance exam for the University of Tokyo to study it. I am also considering going to a graduate school abroad. My plan is to continue to a doctorate. This is a career path I had never even imagined before studying abroad, but I am so glad that I was able to make this decision after studying at UCSD.

>Acknowledgment

I would like to express my appreciation to Ito Foundation U.S.A. and Friends of UTokyo, Inc. for the financial support of this program.

Fig. 7. Geisel Library at UC San Diego, the place where I spend most of my time to study.