Math Problem Statement

Find where the M ̈obius transformation f (z) = z + 1 z − i maps the unit circle, the real axis, and the imaginary axis. Also draw graphs of the unit circle and real and imaginary axes in the z-plane and their images in the w-plane. • Note that you only need to calculate the images of 0, −1, 1, −i, i, and ∞ (note that f (∞) = limz→∞ f (z), assuming the limit exists). • Remember that M ̈obius transformations preserve angles.

Solution

The graphs above show the transformations of the unit circle, real axis, and imaginary axis under the Möbius transformation f(z)=z+1zif(z) = \frac{z + 1}{z - i}.

  • z-plane (left):

    • The unit circle is plotted in blue.
    • The real axis is plotted in red.
    • The imaginary axis is plotted in green.
  • w-plane (right):

    • The transformed image of the unit circle is plotted in blue.
    • The transformed image of the real axis is in red.
    • The transformed image of the imaginary axis is in green.

The Möbius transformation preserves angles, and the unit circle has been mapped into a line-like structure. The real axis and imaginary axis have been transformed into curves in the ww-plane, likely circular arcs.

Would you like to dive into any of these transformations in more detail, or do you have any questions?

5 Related Questions:

  1. What happens to other points inside the unit circle under this Möbius transformation?
  2. How would the transformation behave if zz approaches 0 from different directions?
  3. Can you calculate the inverse of this Möbius transformation?
  4. What is the effect of Möbius transformations on the upper half-plane?
  5. How are Möbius transformations used in complex analysis and geometry?

Tip:

Möbius transformations are conformal, meaning they preserve angles at intersections of curves, making them powerful tools in geometric function theory.

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Math Problem Analysis

Mathematical Concepts

Complex Analysis
Möbius Transformation
Conformal Mapping

Formulas

Möbius transformation: f(z) = (z + 1) / (z - i)
Limiting behavior of f(z) as z → ∞

Theorems

Möbius transformations preserve angles
Möbius transformations map circles and lines into circles and lines

Suitable Grade Level

Undergraduate