Does an Analytic Function Vanishing on a Disc Boundary Vanish Inside?

In summary, The identity theorem for holomorphic functions states that if two holomorphic functions agree on a set with an accumulation point, they are equal on the entire domain. This can also be proven using the Cauchy Integral Formula, which states that the integral of a function around a closed loop is equal to the sum of its values inside the loop. Thus, if an analytic function vanishes on the boundary of a closed disc in its domain, it must also vanish on the full disc.
  • #1
Metric_Space
98
0

Homework Statement




If an analytic function vanishes on the boundary of a closed disc in its domain
, show it vanishes on the full disc

Homework Equations



CR equations?

The Attempt at a Solution



Not sure how to start this one.
 
Physics news on Phys.org
  • #2
Hi Metric_space! :smile:

Have you seen the identity theorem for holomorphic functions. This says

If two holomorphic functions f and g on a domain D agree on a set which has an accumulation point c in D then f = g on all of D.

Did you see something like that? It would immediately give you the answer...
 
  • #3
Interesting ...I'll reread my notes. Thanks!
 
  • #4
Metric_Space said:
Interesting ...I'll reread my notes. Thanks!

You could also use the Cauchy Integral Formula, which is almost certainly in your notes even if micromass' theorem isn't.
 
  • #5
Is it just as simple as applying the Cauchy Integral formula?

ie. it follows directly from the CIF?
 
  • #6
Well, what does the Cauchy Integral Formula say? What if you take the integral to be around the boundary of that disk?
 

FAQ: Does an Analytic Function Vanishing on a Disc Boundary Vanish Inside?

What is complex analysis?

Complex analysis is a branch of mathematics that deals with the study of complex numbers and their properties. It involves the analysis of functions of complex variables and their corresponding derivatives and integrals.

How is complex analysis different from real analysis?

Complex analysis is different from real analysis in that it focuses on the study of functions of complex variables, whereas real analysis deals with functions of real variables. Complex analysis also has its own set of theorems and techniques that are specific to complex numbers.

What are some real-world applications of complex analysis?

Complex analysis has many real-world applications in fields such as physics, engineering, and economics. For example, it is used in the study of electrical circuits, fluid dynamics, and signal processing.

What are some key theorems in complex analysis?

Some key theorems in complex analysis include the Cauchy-Riemann equations, Cauchy's integral theorem, and the Cauchy integral formula. These theorems are fundamental in understanding the behavior of complex functions.

What are some common techniques used in complex analysis?

Some common techniques used in complex analysis include contour integration, power series expansions, and the residue theorem. These techniques are used to evaluate complex integrals and to solve problems involving complex functions.

Similar threads

Back
Top