Conformal Mapping: Finding \phi(z) = z^{0.5}

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Homework Statement


Hi

Is there a rigorous way to find conformal mappins? Say I would like to find how \phi(z)=z^{0.5} maps the domain r\exp(i\phi) (with r>0 and 0\leq \phi \leq \pi), how would I do this?

Thanks in advance.
 
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Niles said:

Homework Statement


Hi

Is there a rigorous way to find conformal mappins? Say I would like to find how \phi(z)=z^{0.5} maps the domain r\exp(i\phi) (with r>0 and 0\leq \phi \leq \pi), how would I do this?

Please don't use the same symbol for two different objects in the same context! Either \phi is a complex function or it's the argument of a complex number. Choose one and stick with it, and find a different symbol for the other.

To answer your question: Start with \phi(re^{i\theta}) = r^{1/2}e^{i\theta/2}. What values can r^{1/2} take if r > 0? What values can \theta/2 take if 0 \leq \theta \leq \pi? What region of the complex plane does that give you?
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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