This is a study note of many body theory. Topics will be selected out of my own interest. 主题部分参考（抄写）知乎大黄猫老师的讲义，用英文是因为不用切输入法打字比较快。未经本人允许请勿传播。It's better to understand than to record.
Self-Consistent Quantum Field Theory notes. Ref Haussmann 2003. Thanks Jiaxin and Yutai for discussion and guidance.