Green function for bilocal operatos?

[Neitrino]

Dear PF,

Could you tell me what is Green function for bilocal operators? As I understand from its form G(x1y1, x2y2,...)... now the pairs of XY are considered as points instead of single X points as in normal Green function
G(x1,x2,x3...). So What do we need it for? Or can it be decomposed into sums/products of ordinary Greens functions? Or where to read about it?

Thks

 

[nbo10]

I've never heard of bilocal operators before, it could just be a difference in terminology. Are you talking about retarded and advanced Greens functions? A greens function can take any number of parameters, normally it's a vector and a time component.