Conformal mapping of an infinite strip onto itself

In summary, the conversation discusses finding a conformal mapping of the strip ##D=\{z:|\Re(z)|<\frac{\pi}{2}\}## onto itself that transforms the real interval ##(-\frac{\pi}{2},\frac{\pi}{2})## to the full imaginary axis. The suggested method of mapping the strip to a unit circle and then back to the strip using a series of functions does not successfully map the interval to the imaginary axis. The speaker suggests using ##sin(z)##, rotating by multiplying by ##i##, and then using ##Arctan(w)## to take the infinite strip back to itself, effectively mapping the interval to the imaginary axis.
  • #1
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Homework Statement


Find a conformal mapping of the strip ##D=\{z:|\Re(z)|<\frac{\pi}{2}\}## onto itself that transforms the real interval ##(-\frac{\pi}{2},\frac{\pi}{2})## to the full imaginary axis.

The Attempt at a Solution


I tried to map the strip to a unit circle and then map it back to the strip. First I used ##f_{1}(z)=2z## to expand the strip to ##\{z:|\Re(z)|<\pi\}## and then I rotated it by applying ##f_{2}(z)=iz##. I then applied ##f_{3}(z)=e^z## to send the region to the unit disk. I then applied ##f_{4}(z)=\frac{1+z}{1-z}## to send the unit disk to the half plane ##\{z:\Re(z)>0\}## and then I applied ##f_{5}(z)=Log(z)## to send that back to ##\{z:|\Im(z)|<i\frac{\pi}{2}\}##. I then applied ##f_{2}## once more to rotate it back to the strip ##D=\{z:|\Re(z)|<\frac{\pi}{2}\}##.

After composing all these functions, I ended up with something along the lines of ##-z## which might even be ##z## depending on whether or not I messed up a sign somewhere in the calculations. This doesn't map the interval to the imaginary axis. Can someone help me include that part?

EDIT**: I know that the easiest way to map the strip to itself is by using ##z,-z## but that doesn't help me map the interval to the imaginary axis. I was hoping that something magical would happen in the mess up there but nothing happened...
 
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  • #2
I figured it out for future reference to anybody.

Use ##sin(z)## to take the infinite strip to ##\mathbb{C}\sim\{w:|\Re(w)|\geq 1## and ##\Im(w)=0\}##. Then rotate this by multiplying by ##i## and finally use ##Arctan(w)## to take it back to the infinite strip.
 

Related to Conformal mapping of an infinite strip onto itself

1. What is a conformal mapping?

A conformal mapping is a mathematical function that preserves angles between curves. In other words, it is a mapping that maintains the shape of a figure while stretching, shrinking, or rotating it.

2. How is an infinite strip mapped onto itself?

An infinite strip can be mapped onto itself using a conformal mapping called a strip map. This mapping involves taking a point on the infinite strip and projecting it onto a unit circle, then extending that point to the opposite side of the strip. This process is repeated for all points on the strip, creating a conformal map.

3. What are the benefits of conformal mapping of an infinite strip onto itself?

Conformal mapping of an infinite strip onto itself has various applications in mathematics and physics. It allows for the study of complex functions on an infinite strip, which can provide insights into real-world phenomena such as fluid flow and electrical currents.

4. Is conformal mapping of an infinite strip onto itself reversible?

Yes, conformal mapping of an infinite strip onto itself is reversible. This means that the original infinite strip can be obtained by applying the inverse of the conformal mapping function to the mapped strip.

5. Are there any limitations or restrictions on conformal mapping of an infinite strip onto itself?

Yes, there are limitations on conformal mapping of an infinite strip onto itself. The mapping may not be possible if the infinite strip has a boundary with a complex geometry, or if it is not bounded by straight lines. Additionally, the mapping may not be conformal at certain points on the strip where the derivative of the mapping function is equal to zero.

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