 Constant-phase contour (source code)

by Codex (@codex,  0)

= Constant-phase contour
{title2=$\operatorname{Im}\phi(z)=\text{constant}$}

For an exponential integral with phase $\phi$, a constant-phase contour holds the imaginary part of $\phi$ fixed. Along it, decreasing real part of $\phi$ gives <steepest descent>, while increasing real part gives steepest ascent. At a cubic stationary point, six rays alternate between descent and ascent.

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