Many failures and difficulty in understanding general relativity, quantum field theory, and conformal field theory

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

• A. Zee’s group theory book, which discusses the mathematical language to study symmetry, and
• X.-G. Wen’s quantum field theory book, focusing on the field techniques when dealing with quantum many-body systems.

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…).

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I was trained to be a structural engineer but I want to be a theoretical physicist.

I was major in Japanese when I was a freshman in 2013. It was exciting and happy to study with so many young girls together: there are about 50 students who were major in Japanese but only five fellows! For a boy focusing on science side in high school in China, he had hardly seen over 10 girls during his whole high school life. Such a situation could not be better! Sadly, the boy read too many science popular books and was more curious about peculiar quantum mechanics, or even string theory at that time, so he decided to change his major. He first did some research on physics major in his university, but it turned out the people in the physics department look nothing like the characters in his book: Niels Bohr, Wolfgang Pauli, Richard Feynman, Albert Einstein, etc. As a result, he had to take the second best and went to civil engineering major, hoping he could meet more geek-like people there, since it was (and still is) the department with the most eminent professors and students in the country. He started his undergraduate training in structure engineering in 2014.

Here are a few things that I want to achieve in 2019.

Non-physics

I hope I can finish writing up my master thesis before September. The plan is to finish the first draft before mid July, and working on its revision starting from mid August.

About Physics

I’m so happy that The University of Tokyo (UTokyo) gives me one graduate school offer, so I can start my physics journey! Before attending UTokyo in September this year, I still need to learn more physics on my own. Here are my plans for first half year:

I learned a lot of physics in 2018, and here is a summary!

First Half the Year

In January, I finished 8.04x, Quantum Mechanics an online course provided by MITx and got perfect grades, 92, 94, and 88 for three exams. 8.04x was lectured by Professor Barton Zwiebach, whose doctoral advisor is Murray Gell-mann. This course introduced basic concepts of Quantum Mechanics and did standard 1-D potential examples, such as square wells, Dirac-delta potential and harmonic oscillators, along with several important theorems for 1-D potential. Besides, it gave a detailed treatment on scattering states in 1-D, covering topics like time delay, Levinson’s theorem and resonance. The course ended with central potential and Hydrogen Atom. It was a challenging but rewarding course, and of course, interesting! What makes this course stand out among all other online courses is its active discussion forum. I met lots of interesting physics and math geeks there, Mark, Jolyon, Jim, BlueFlow and Jonathan, and the discussion about physics with them made my learn experience vivid and lovely (Actually, I read their discussions in forum most of the time). Later in September 2018, Jim offered me an unexpected research experience, which was the first time I worked with a real physicist!