I am a PhD student at University of Illinois Urbana-Champaign majoring in Physics. I built this website (source code here) to share my understanding of things (mostly interesting theories) I have learned. The most recent notes are often in progress, for I like to keep a few projects running at the same time. You are always welcomed to comment on my posts for suggestions or discussions. Some of the old notes were written in Chinese. You can learn more at the about page.