Conformal modulus of an annulus
= Conformal modulus of an annulus
{title2=$M=(2\pi)^{-1}\log(R/r)$}
The height divided by circumference in a conformal Euclidean cylinder model of an <annulus>. For $r<|z|<R$, it is $(2\pi)^{-1}\log(R/r)$. The <extremal length> of winding-one core curves is $1/M$, whereas that of curves joining the two boundary components is $M$.