This is a collection of my developing understanding of basic aspects of QFT. Some might seem to be trivial and silly, but I still hope some of them can be helpful for you : )
Clarifying the notion of bubble diagrams in the path integral.
May not be updated any more...
Derivation of conformal Ward identity
A little trick to compute trace in Fock space.
A brief review on Maldacena-Nunez's no-go theorem.