Stress-tensor operator-product expansion
= Stress-tensor operator-product expansion
{title2=$T(z)T(w)$ OPE}
In a two-dimensional conformal field theory,
$$
T(z)T(w)\sim\frac{c/2}{(z-w)^4}+\frac{2T(w)}{(z-w)^2}+\frac{\partial T(w)}{z-w}.
$$
The fourth-order pole is the central extension, while the remaining poles express that $T$ has conformal weight two.