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What is it like to be a Ph.D. student at Kavli IPMU, in particle theory, with TW as an advisor?

The admission channels I am committed to

        The Graduate School of Science at the University of Tokyo adopts a two-stage system in all of the addmission options for international students. Before the official selection by the Graduate School of Science, the applicants need to clear the pre-selection process run by individual faculty members appointed at the Graduate School of Science. In 20xx autumn, for students enrolling in September 20xx+1, I myself(Watari) and some other faculty members of the Physics Major Course run this pre-selection process jointly. If you are interested in choosing me as a prospective advisor, then you are invited to proceed to the page of the joint pre-selection process and follow the instruction there.

        As a default policy of my own, I am open to the admission options for international students starting their Ph.D. course in October (not for students starting in April). There are still a few admission options that the University of Tokyo offers. Among them, I open my window only through the GSGC course and the regular course (but not through the Government scholarships). I must ask for your understanding.
exceptions to this defaulty policy: have a look at the "Master Thesis and..." section

        Also as a policy of my own, I welcome international students to the Ph.D. program only from the Master course, not directly into the Doctor course; this policy is also applied to domestic students. I know that some of the applicants have been finishing a Master course elsewhere at the time applying for the graduate study at U. Tokyo, but still I maintain this policy; see additional remark in the "Master Thesis and..." section below.

For Students Applying for the Enrollment in October, 2025

I will not host a new graduate student starting in October, 2025. Please consider other faculty members in a similar field.


Master Thesis and Qualification for the Doctor Course

There are a lot of things to learn in theoretical particle physics. So, in theoretical particle physics at the Physics Major Course, we do not necessarily require a graduate student to have produced an original scientific result for a master thesis. It suffices to write up a review article on a topic in this field to prepare himself/herself ready to be engaged in reserach projects soon after the master thesis defense.

We require (at least I definitely do), though, that a student has acquired basic ethics and skills of scientists, including honesty about what she/he is not sure about---(*), skills of critical thinking, logical thinking, and of exchanging ideas clearly (not just absorbing knowledge), by the end of the Master Course. If we are not sure whether a graduate student has been achieving that, we might recommend the student to leave academia without proceeding to the Doctor course.

(*) has been the first principle of academia, in Western as well as Asian World, not just in humanity but also in natural science.
      (Confucius) To take the things you know as what you know, and things you are not sure about as what you do not know yet, --- this is to know things. 知之為知之, 不知為不知. 是知也.
      (R. Feynman, a commencement address) The first principle is that you must not fool yourself, --- and you are the easiest person to fool.

As I wrote earlier (above), I ask all the students to go through this master thesis defense, even when one has finished a master course elsewhere before coming to the University of Tokyo graduate school. If such a student shows good enough performance, then we have an option to shorten the whole Ph.D. program (master course + doctor course) by 1 year.

We will authorize shortning the master course when the criterion above is met. It is not always the best option to do so for graduate students, though, because most of scholarship options in Japan for the doctor course (the latter half of the Ph.D. program) do not cover extension beyond three years in the doctor course; graduate students need to be "ready" when entering the doctor course. An option of shortning the doctor course is approved by the Physics Major Course for truly outstanding students (on average, one student in five years or so?).

Exception:     We often receive inquiries, often from master course students in Europe, whether there is an option to enroll directly into the Doctor course at U Tokyo. Such an option is not ruled out by the department, but it is widely perceived in Japan (like in north America) that the default is to go through both the Master's and Doctor course at one univeristy, than to change places in between.

Master students from Europe often point out that doing Master's program again at U Tokyo would come with the duty of taking class-room lectures, writing Master's thesis, and at least one year of time, maybe two. They focus on the cost of repeating Master's program at U Tokyo. There are also risks and downsides in skipping Master course at Tokyo (or other places), however.
First, any university has to control quality of its Ph.D.s; the qualifying exam / master thesis defense plays an important role in the quality control in the system of North America and Japan. The admission process to the Doctor course cannot play the same role. Bypassing the QE would only mean that an equivalent decision for quality control is postponed until the last moment of the PhD program. That is a risk for both students and faculty members.
Second, the default 3 year period for the Doctor course is often too short to gain specialization to be able to stand solidly at the frontier of some research field. By starting specialization in one research subject during the Master course, and keep going in the remaining 3 years, students in the system of Japan/North America gain solid standing in their research more easily at the time they finish PhD and enter into the labor market of postdoctoral fellows. Students in the European system often change research subject when starting the Doctor course elsewhere, spnding extra time to gain pre-requisite knowledge within the 3 years at Doctor course. This is a non-negligible issue especially in a technically-heavy field such as string theory. This will be a disadvantage in the posdoc market (although exposure to two different research subjects at the earliest stage might be rewarded later in the carreer??).
Finally, scholarships available to Doctor course students in Japan are not flexible enough to be extended beyond the typical 3 year period in the Doctor course. Even when a student wants to spend the 4th year at the Doctor course in Japan (to be stronger before embarking into the postdoc market), there is no financial support. There could have been a financial support all through the 4 years, if the same 4 years were spent as 1 year in the Master course and 3 years in the Doctor course.
To add more at the very end, the GSGC fellowship at the University of Tokyo is avaiable only to students who start from the Master course and continue to the Doctor course, not to students who enroll directly in the Doctor course.

For all those reasons, I do not think it is a good idea (for both me and students) to welcome an international student directly into the Doctor course at the University of Tokyo. Exceptions that I can imagine will be the case of students who did Master program at a university with a quality requirement similar to that at U. Tokyo, under supervision by a faculty member with whom I wrote papers together before, or whose results I heavily use in my recent research papers. Only in such situations I can imagine that the risks above are reduced significantly.

When a student in such an exceptional situation is interested in doing Doctor course by joining my group at U Tokyo, please write an email to me. The pre-selection process has to be carried out separately form the one run by all the particle-theory faculty members; I will not rule out Government scholarship and other options for financial suport (because the GSGC fellowship is not available).

What Kind of Topics Do I Work On?

See this page for my reserach interests.

How to Get into the Stage of Research, when I Serve as Your Adviser

My students are usually invited to join one of research porjects I have in their 2nd half of the 1st year of the Ph.D. program; they are often occupied with taking courses in the 1st half of the 1st year. It is often very difficult at that stage to be the leading player in a collaboration on research topics in string theory, but that is fine. As students grow up and gain power, I gradually change my role from leading a collaboration to supporting students leading a collaboration. When a student shows an outstanding growth curve, I will recommend him/her to try to complete a project by onselef, or to have an opportunity to work with other experienced scientisits.

The research projects that I invite a 1st-year student to is likely to be one of the topics at the beginning of the page (my research interests).

If You Wish to Work in an Area of String Theory Close to Mathematics...

I use math heavily in my research projects. That will be clear from the information in the page (my research interests).

I recommend (and also assume) that students working with me on research projects have read at least one math textbook, preferrablly a bit more, before coming to the graduste school of U. Tokyo.

Math is not the same as physics, especially in that we are allowed to conclude in physics that something is "roughly OK" based on intuitions, or "presumably correct when all things considered," whereas not much value is given to such observations in mathematics. With the physics approach, we can get things done faster, but too much indulgence in the culture of "presumably roughly OK" might take us away from tough and solid logical reasonings. An experience of reading a math textbook line by line, by filling the logic between the lines, is a good way to maintain loose contact with the math-department culture requiring solid logical foundation.