I try to learn QFT
I tried to follow the video lectures of the MIT course 8.962 about general relativity (GR) back in September 2020 after its release on MIT/OCW. I only got to the point of Lecture 9 about Geodesics back then. The feeling wasn’t right. I thought I wasn’t prepared then.
It has been half a year since my last post, and I forgot to post a plan for the year 2022. So first some recent updates about my physics study.
Our research group has a weekly textbook reading session, where we choose a textbook each year and study it together. In last two years, we have chosen
This year, we have chosen John Preskill’s lecture notes on quantum information and quantum computation. It’s a journey to the strange and crazy quantum world.
There are many approaches to classical mechanics. The first introduction in high school is intuitive and fit into our everyday experience: motion of a single particle is some trajectory in ordinary space and we are interested in finding its time evolution. This formulation relies heavily on notions like particles, force, velocity and acceleration.
However, even in high school physics class, the discussion doesn’t limit itself to intuitive notions. We are seeing very abstract concepts like energy and momentum. These conserved quantities are very powerful tools to make our analysis simple and elegant. Moreover, it provides a deeper understanding of a physical problem.
I started Prof. Sachdev’s Havard course Physics 295b: Quantum Theory of Solids in the end of October 2021, and finished the first 30 lecture videos in the beginning of February 2022. For me, this course feels like the ideal next step after learning the usual undergraduate solid state physics course (talking about things like nearly free electron model, tight-bonding model, bond structure, X-ray or neutron scattering experiments…).
One of my plans for non-physics life for year 2021 is to study more about Existentialism. See the last paragraph of my new-year-plan post this year. For those who never heard about the word Existentialism, it is a philosophy discussing how to live a meaningful life. The ideas from existentialism have an impact on theory of psychology. Actually, it is my reading of a psychology novel called When Nietzsche Wept in March (maybe?) this year that revivified my interest and passion about Existentialism and made me think deeply about meaning of life.
I want to set a few non-physics goals for this year.
Dipping my toe into other fields always enriches my life. During my undergrad study in Tongji University, it was my custom to choose at least one non-technical courses each semester. Usually, they are about philosophy, musics, culture, and communications. Even in my most busy semester during sophomore year, when I need to take almost twice the credits of course as much as an ordinary fellow student, I still stick to my custom and attend a class about 20th-century Chinese culture on Wednesday and also a weekly concert on Thursday evening (see my course schedule of that semester below). These two classes really made this otherwise very technical semester more colorful!
I finally finished watching all the video lectures of the famous Harvard lecture about political philosophy called Justice on 23 March. In 24 lectures, each about 25 minutes, Professor Michael Sandel discusses a straightforward question: What’s the right thing to do?*
His class is not at all like any ordinary philosophy lectures, which are probably either dull or mysterious. Instead, Prof. Sandel will bring up lots of vivid examples to force you to think about general moral principles. It is a Socratic-questioning-style class, which is my favorite form of lecture. You can watch all the video lectures in its official website. For people who are more comfortable with Chinese, you can find these videos in Bilibili, though I should warn you the translation of the subscript is not perfect. I recently notice that this course has its edX version and video transcripts are available in Chinese. I will definitely go through this edX version in the future.
February this year was a happy period. Chinese new year came on 12 Feb., so we have many small dinner parties in the dormitory. However, physics learning has never stopped. I finally find time to finish the last condensed matter course in PSI program: PSI18-19 Condensed Matter Review lectured by Professor Alioscia Hamma. Other two condensed matter courses are reviewed in my previous posts, one covering entanglement in many-body systems and tensor network states, the other covering magnetism. Notice the first one has a more convenient online course form.
Two friends of mine, Yuan Yao and Weiguang Cao, started to read the book, A First Course in String Theory by Barton Zwiebach, a few weeks ago. Barton Zwiebach is my good-old professor in 8.04x — 8.06x quantum mechanics course series. I like his lectures very much, so join my two friends.
This textbook is based on an undergraduate course Prof. Zwiebach gives in MIT (with course number 8.251). The syllabus, readings and assignments of the course can be found in MIT’s OCW website here. Although this OCW course does not provide lecture videos, perimeter institute has recorded Prof. Zwiebach’s lectures in PSI lectures of 2012 — 2013. This lecture videos can be found in the review tag of this website.
For my first research project here at the University of Tokyo, the analysis was finished in early November and the first draft of the paper came out in middle December. Besides, I took a few online courses and finished one books on field theory of condensed matter physics by Shankar.
After some simple evaluations of the correctness of our idea, I started to spend most of my time working on the research project at the end of June. It was interrupted when I moved to the new dormitory KIV in July but I picked up quickly after setting down in early August.