Uniqueness of Holomorphic Functions

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SUMMARY

The discussion centers on the uniqueness of holomorphic functions, specifically demonstrating that if two holomorphic functions, f and g, are defined in a connected open set D and have no zeros, then a constant c exists such that f = cg in D. The condition for this conclusion is based on the equality of the derivatives of f and g at a sequence of points approaching a limit point a. The participants clarify the meaning of "identically zero," emphasizing that if a holomorphic function's derivatives of all orders vanish at a point, the function must be zero throughout the connected set.

PREREQUISITES
  • Understanding of holomorphic functions and their properties
  • Knowledge of complex analysis, specifically the concept of limits and derivatives
  • Familiarity with the definition of connected open sets in the complex plane
  • Basic grasp of the implications of the identity theorem in complex analysis
NEXT STEPS
  • Study the identity theorem in complex analysis
  • Explore the properties of holomorphic functions and their derivatives
  • Learn about the implications of zeros of holomorphic functions in connected domains
  • Investigate the concept of uniform convergence in the context of holomorphic functions
USEFUL FOR

Students and researchers in complex analysis, mathematicians focusing on holomorphic functions, and educators teaching advanced calculus or complex variables will benefit from this discussion.

Wretchosoft
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Homework Statement

Let f and g be two holomorphic functions in a connected open set D of the plane which have no zeros in D; if there is a sequence an of points such that lim an = a and an does not equal a for all n, and if

f'(an)/f(an)=g'(an)/g(an)

show that there is a constant c such that f=cg in D.

Homework Equations

If f is identically zero at a point in a connected open set, then f is identically zero on the whole set.

The Attempt at a Solution

I have shown that (f/g)'(a) = 0, but I don't see how that would imply that the derivative is identically zero at that point.
 
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I don't know what you mean by "identically 0 at a point"! "Identically" zero means zero at every point of some set. Are you sure you have quoted your "relevant equation" correctly?
 
HallsofIvy said:
I don't know what you mean by "identically 0 at a point"! "Identically" zero means zero at every point of some set. Are you sure you have quoted your "relevant equation" correctly?

Ah, sorry. What I mean is that the derivatives of f of every order are 0 at that point, so that f is equal to the zero function at that point. I may be abusing the term.
 

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