string theory, the first update after three months

I did'nt update here for three months. And a projection about string field theory, it's an interesting title. From it , CFT is very important in the string theory and string field theory. But i have one day in a week that can be used in this problem. I'm sad.

After i finish the fee's problem,
I will do my best on this question. And a note about polchinski' book will be released, the note contains the calculation's detail, Of caurse, it contains the first two chapters...