Equation Icon  ⟨hab(x )hcd(y)⟩s = ⟨h0 (x)h0 (y)⟩s + ab ∫cd ∘ ---------- (8πG )2 d4x′d4y′ g(x′)g(y′)Gret (x,x ′)N efgh(x′,y ′)Gret (y,y′) abef cdgh ≡ ⟨hab(x)hcd(y)⟩int + ⟨hab(x)hcd(y)⟩ind. (17 )