Hey guys, I have a doubt.
I was wondering if it is possible to have a generating function Z[J] where its integral has not a linear dependence on J(t), but a quadratic or even cubic dependence, like Z[J]=∫Dq exp{S[q] + ∫ J²(t) q(t)dt}, and how this would alter the calculation of the n-point...
If a have ln Z[J] = ∫ J²f(t)dt+ a∫ J³dt + b∫ J^4dt, where J=J(t), and I would like to get the 3-point and 4-point functions, how do I proceed?
I have tried to use the regular formula for the n-point function, when you derive Z[J] n times in relation to J(t_1)...J(t_n) and after applies J=0...