I have a question regarding equation (2.22) in Ginsparg's lecture notes on CFTs. Equation (2.22) is ⟨T(z)ϕ1(w1,ˉw1)⋯⟩=n∑i=1(hi(z−wi)2+1z−wi∂∂wi)⟨ϕ1(w1,ˉw1)⋯⟩
My question is - Is (2.22) correct?
Here are my reasons to believe that it is not -
I believe he derives (2.22) from (2.21) by setting ϵ(x)=1x−z in (2.21). (2.22) is then derived if the following holds ⟨∮dx2πiT(x)x−zϕ1(w1,ˉw1)⋯⟩=⟨T(z)ϕ1(w1,ˉw1)⋯⟩
This would be true if the integrand on the LHS had only a pole at x−z. However, it has also has poles at each x=wi, but those contributions aren't considered.I can try and derive (2.22) in a different way - namely via contractions. I start with the LHS of (2.22) and contract T(z) with each ϕi. Each contraction is replaced with the operator product T(z)ϕi(wiˉwi)=hiϕi(wiˉwi)(z−wi)2+∂ϕi(wiˉwi)z−wi+:T(z)ϕi(wiˉwi):
Again, if I only consider the singular terms, I reproduce the RHS of (2.22). But what about :T(z)ϕi(wiˉwi):?? In a general CFT, conformal normal ordering : : is not equivalent to creation-annihilation normal ordering ∘∘ ∘∘. The latter would vanish in a correlation function, but not the former. So, I believe in general there would be extra terms on the right of (2.22).
What am I misunderstanding?
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