Schwarzian derivative
= Schwarzian derivative
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{title2=$\{f,z\}$}
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The Schwarzian derivative is
$$
\{f,z\}=\frac{f'''(z)}{f'(z)}-\frac32\left(\frac{f''(z)}{f'(z)}\right)^2.
$$
It is the inhomogeneous term in the finite conformal transformation of a stress-energy tensor with nonzero central charge.