Search the corpus

    Mapping $\DD^c \cap \HH$ conformally onto $\HH$ with prescribed boundary values

    E-3GIQS

    Area
    Complex Analysis
    Topics
    Conformal Maps, Fractional Linear Transformations
    Status
    draft

    Map \(\DD^c \intersect \HH\) to \(\HH\), sending

    • \(-1\to -1\)

    • \(i\to 0\)

    • \(1\to 1\)

    Solution

    The Joukowski map \[ J(z)={1\over 2}\qty{z + \inverseof{z}} \] does this. For \(z=re^{i\theta}\) with \(r>1\) and \(0<\theta<\pi\), \[ \Im J(z)={1\over2}\qty{r-\inverseof{r}}\sin\theta>0, \] and \(J\) is injective on \(\theset{\abs z>1}\) with image \(\CC\setminus[-1,1]\), so \(J\) maps \(\DD^c\intersect\HH\) bijectively onto \(\HH\). Moreover \(J(-1)=-1\), \(J(i)=0\) and \(J(1)=1\).