Charles Clark

The color encoded phases of $\mathrm{\Gamma}\left(z\right)$ (above) and $\psi \left(z\right)$ (below), are constrasted in the negative half of the complex plane.

In the upper half of the image, the poles of $\mathrm{\Gamma}\left(z\right)$ are clearly visible at negative integer values of $z$: the phase changes by $2\pi $ around each pole, showing a full revolution of the color wheel. This pattern is analogous to one that would be seen in fluid flow generated by a semi-infinite line of vortices.

In the lower half of the image, the poles of $\psi \left(z\right)$ (corresponding to the poles of $\mathrm{\Gamma}\left(z\right)$) and the zeros between them are clear. Phase changes around the zeros are of opposite sign to those around the poles. The fluid flow analogy in this case involves a line of vortices of alternating sign of circulation, resulting in a near cancellation of flow far from the real axis.

© 2010–2014 NIST / Privacy Policy / Disclaimer / Feedback;
Version 1.0.7;
Release date 2014-03-21.
A printed companion is available.
5.24 Software6 Exponential, Logarithmic, Sine, and Cosine Integrals