Branch Cut for (lnz)^2: Determining Branch Points and Range

In summary, the conversation discusses the homework statement of whether the function ln(z) goes from 0 to ∞ and the proper way to determine branch points of a function. The question about the domain of ln(z) is clarified and it is mentioned that branch cuts can be made arbitrarily as long as they make sense. However, the speaker personally prefers to use Riemann surfaces.
  • #1
CrimsonFlash
18
0

Homework Statement


It is simply the same as the one for lnz i.e. does it go from 0 to ∞?
Also, is there any proper way to figure out branch points of a function?

Homework Equations





The Attempt at a Solution

 
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  • #2
bump?
 
  • #3
CrimsonFlash said:

Homework Statement


It is simply the same as the one for lnz i.e. does it go from 0 to ∞?
Also, is there any proper way to figure out branch points of a function?
Do you mean, "Does z go from 0 to ∞?" Your question is unclear, which is why no one will answer.

Generally, branch cuts can be made fairly arbitrarily as long as they make sense. Though, I personally prefer to use Riemann surfaces because they are more fun for me.
 
  • #4
Certainly if you have a domain where ln(z) is defined holomorphically, then ln(z)2 is also holomorphic on the same domain
 
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  • #5
Ok thanks.
 

Related to Branch Cut for (lnz)^2: Determining Branch Points and Range

1. What is a branch cut for (lnz)^2?

A branch cut for (lnz)^2 is a mathematical concept used in complex analysis to define the multi-valued function lnz. It is a line or curve on the complex plane where the function is discontinuous and needs to be "cut" in order to make it single-valued.

2. Why is a branch cut necessary for (lnz)^2?

A branch cut is necessary for (lnz)^2 because lnz is a multi-valued function, meaning it can have multiple values for a single input. This can cause issues in mathematical calculations, so a branch cut is used to define a specific range of values for lnz and make it single-valued.

3. How is a branch cut chosen for (lnz)^2?

The branch cut for (lnz)^2 is typically chosen along the negative real axis, starting at the origin and extending to negative infinity. This is known as the principal branch cut and is the most commonly used branch cut for lnz.

4. What is the relationship between a branch cut and a branch point?

A branch cut and a branch point are closely related concepts. A branch point is a point on the complex plane where a function becomes multi-valued, while a branch cut is the line or curve used to make the function single-valued. Branch points are often located at the endpoints of branch cuts.

5. How does the branch cut affect the values of (lnz)^2?

The branch cut for (lnz)^2 affects the values of the function by restricting them to a specific range. For example, the principal branch cut for lnz allows the function to have values between 0 and 2π, while other branch cuts may have different ranges. This ensures that the function remains single-valued and avoids any mathematical inconsistencies.

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