This is a question for anyone who is familiar with Di Francesco's book on Conformal Field theory. In particular, on P.108 when he is deriving the general form of the 2-point Schwinger function in two dimensions. He writes that the most general form of the tensor is Sμνρσ=(x2)−4{A1gμνgρσ(x2)2+A2(gμρgνσ+gμσgνρ)(x2)2+A3(gμνxρxσ+gρσxμxν)x2+A4xμxνxρxσ}
This I understand and have obtained this result myself. What I don't understand however, is why he has neglected the following term since it seems to satisfy all the constraints presented on P.108:
Sμνρσ=A5(x2)−3(gμσxρxν+gμρxσxν+gνσxρxμ+gνρxσxμ)
In another thread I posted here, I wondered whether this could be reduced to terms already present in the form Di Francesco gave, but I was quickly reassured this to not be the case. So, if anyone is familiar with his book and would be willing to clarify this it would be great. I asked a professor at my university and he was not sure either why it has been neglected, so I thought I would pose the question here. Many thanks.
This post imported from StackExchange Physics at 2014-09-12 20:19 (UCT), posted by SE-user CAF