Basic Complex Analysis: Cauchy Riemann

In summary, the conversation discusses using the Cauchy Riemann equations to prove that the imaginary part of a holomorphic function in the unit disc with a constant real part is also constant. The unit disc being connected and the mean value theorem are mentioned as additional tools that can be used to support the proof.
  • #1
snipez90
1,101
5

Homework Statement


Let f be a holomorphic function in the unit disc D1 whose real part is constant.
Prove that the imaginary part is also constant.

Homework Equations


Cauchy Riemann equations


The Attempt at a Solution


Hi guys, I'm working through the basics again. I think here we just need to use Cauchy Riemann and the fact that the unit disc D1 is connected?
 
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  • #2
C-R equation should suffice given the real part of an analytic function is constant.
 
  • #3
Yes I thought so, thanks. I knew this was a basic fact even though there are similar sounding problems that often use other tools. Anyways I guess the details are just an application of the mean value theorem.
 

FAQ: Basic Complex Analysis: Cauchy Riemann

1. What is Cauchy-Riemann equation in complex analysis?

The Cauchy-Riemann equation is a set of necessary conditions for a complex-valued function to be differentiable at a point in the complex plane. It states that the partial derivatives of the real and imaginary components of the function must satisfy a specific relationship, known as the Cauchy-Riemann equations. This equation is important in complex analysis as it allows for the study of complex differentiability and the development of the Cauchy integral theorem and Cauchy integral formula.

2. How are the Cauchy-Riemann equations derived?

The Cauchy-Riemann equations are derived from the definition of complex differentiability. By expressing a function in terms of its real and imaginary components, and using the definition of a limit, the Cauchy-Riemann equations can be obtained. This derivation is important as it provides a deeper understanding of the conditions for complex differentiability and their implications.

3. What is the significance of the Cauchy-Riemann equations in complex analysis?

The Cauchy-Riemann equations are significant in complex analysis as they provide necessary conditions for a complex function to be differentiable. This allows for the development of important theorems and formulas, such as the Cauchy integral theorem and formula, which are essential in the study of complex analysis and its applications in fields such as physics and engineering.

4. Can the Cauchy-Riemann equations be used to determine whether a function is analytic?

Yes, the Cauchy-Riemann equations can be used to determine whether a function is analytic. If a function satisfies the Cauchy-Riemann equations at a point, then it is differentiable at that point and hence analytic. However, it is important to note that satisfying the Cauchy-Riemann equations is a necessary condition, but not a sufficient one, for a function to be analytic.

5. Are the Cauchy-Riemann equations valid for all complex functions?

No, the Cauchy-Riemann equations are only valid for certain types of complex functions, namely those that are differentiable. If a function is not differentiable, then the Cauchy-Riemann equations do not apply. Additionally, the Cauchy-Riemann equations do not apply at points where the function is not defined, such as at singularities.

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