Complex Analysis Concept Question

The Cauchy-Riemann equations are useful in disproving differentiability, but they do not guarantee it. Conversely, if a function is known to be differentiable, then the Cauchy-Riemann equations must be satisfied. In summary, the existence of the satisfaction of the Cauchy-Riemann equations alone is not enough to guarantee differentiability, but if the partial derivatives are continuous and the Cauchy-Riemann equations are satisfied, then the function is differentiable. Similarly, if a function is known to be differentiable, then the Cauchy-Riemann equations must be satisfied. The Cauchy-Riemann equations can be used to disprove differentiability, but they cannot prove it.
  • #1
tylerc1991
166
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Homework Statement



Just to make certain that I am understanding this correctly, given a function f(z) = u(x,y) + iv(x,y), the existence of the satisfaction of the Cauchy-Riemann equations alone does not guarantee differentiability, but if those partial derivatives are continuous and the Cauchy-Riemann equations are satisfied then this is sufficient conditions for the function to be differentiable? Conversely, given a function that is known to be differentiable, the satisfaction of the Cauchy-Riemann equations must exist? So essentially the Cauchy-Riemann equations are useful in disproving the existence of differentiability of some functions, but cannot necessarily prove differentiability of others? Thank you for your help.
 
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  • #2
Yes, you are correct. A function is complex differentiable if and only if the partial derivatives are continuous and satisfy Cauchy-Riemann.
 

1. What is complex analysis?

Complex analysis is a branch of mathematics that deals with the properties and behavior of complex numbers, which are numbers that can be expressed as a combination of a real number and an imaginary number. It involves studying functions of complex variables and their derivatives, integrals, and series.

2. What is the difference between a real number and a complex number?

A real number is a number that can be represented on a number line, while a complex number is a number that can be expressed as a combination of a real number and an imaginary number (in the form a + bi, where a and b are real numbers and i is the imaginary unit).

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

The Cauchy-Riemann equations are a set of conditions that a complex function must satisfy in order to be differentiable. They are important in complex analysis because they provide a way to determine if a function is analytic (or holomorphic) at a given point, which is essential for many applications in complex analysis.

4. Can complex analysis be applied to real-world problems?

Yes, complex analysis has many real-world applications, particularly in physics and engineering. It is used to solve problems involving electric circuits, fluid dynamics, and quantum mechanics, among others.

5. What are some common techniques used in complex analysis?

Some common techniques used in complex analysis include contour integration, power series, the Cauchy integral theorem, and the residue theorem. These techniques are used to evaluate complex integrals, find solutions to differential equations, and determine the behavior of complex functions.

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