Why is ##\frac{1}{\sqrt{z}}## a branch point and ##\frac{1}{z}## a pole?

In summary, the conversation discusses the difference between a branch point and a pole, and why Cauchy integral theorem cannot be used when there is a branch point. The answer explains that ##\frac{1}{\sqrt{z}}## is double valued and requires a branch cut on the Riemann surface with two sheets. The problem occurs when taking a circle around the point ##z=0##.
  • #1
LagrangeEuler
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I am a bit confused. Why ##\frac{1}{\sqrt{z}}## is branch point and ##\frac{1}{z}## is pole. And why we cannot use Cauchy integral theorem when we have branch point? Why we need to cut off branch point when we integrate? Thanks a lot for the answer.
 
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  • #2
[itex]\frac{1}{\sqrt{z}}[/itex] is double valued. Riemann surface has two sheets - branch cut needed.
 
  • #3
Yes I now that the problem is because is double valued. However I am not sure what is really happens. For example taking the circle around the point ##z=0## problem occurs. Could you explain where is the problem?
 

Related to Why is ##\frac{1}{\sqrt{z}}## a branch point and ##\frac{1}{z}## a pole?

1. What is the difference between a pole and a branch point?

A pole is a singularity in a complex function where the function approaches infinity, while a branch point is a point in the complex plane where the function is not well-defined and can take on multiple values.

2. How do poles and branch points affect the behavior of a complex function?

Poles and branch points can affect the behavior of a complex function by causing it to have discontinuities or multiple branches. They can also influence the convergence and divergence of the function.

3. Can a pole also be a branch point?

Yes, a pole can also be a branch point. In fact, a pole is a special type of branch point where the function has an infinite number of branches.

4. How can we determine the location of poles and branch points in a complex function?

We can determine the location of poles and branch points by analyzing the behavior of the function near singular points, using techniques such as the residue theorem and the Cauchy-Riemann equations.

5. What is the significance of poles and branch points in complex analysis?

Poles and branch points play a crucial role in complex analysis, as they can help us understand the behavior of complex functions and their properties. They are also important in applications such as signal processing and physics.

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