A property of meromorphic functions (?)

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Discussion Overview

The discussion centers around the properties of meromorphic functions, specifically whether two meromorphic functions with the same simple poles and zeros are proportional. Participants explore the implications of this statement and the representation of meromorphic functions as ratios of holomorphic functions.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the truth of the statement regarding proportionality of meromorphic functions with the same poles and zeros, seeking clarification.
  • Another participant asserts that all meromorphic functions can be expressed as the ratio of two holomorphic functions, suggesting that if two functions share the same zeros and poles, they must differ only by a multiplicative constant.
  • A different participant agrees that meromorphic functions can be expressed as ratios of holomorphic functions but challenges the assertion about the representation of holomorphic functions, stating that they cannot always be expressed solely as products of monomials and may include exponential terms.
  • A later reply introduces a potential counterexample involving the functions \( e^z \) and \( e^{2z} \), questioning whether this serves as an example against the initial claim.

Areas of Agreement / Disagreement

Participants express disagreement regarding the truth of the statement about proportionality of meromorphic functions with the same poles and zeros. There are competing views on the representation of holomorphic functions and the implications for meromorphic functions.

Contextual Notes

Participants note that the representation of holomorphic functions may involve additional terms beyond simple products of monomials, which introduces complexity to the discussion. The implications of exponential functions in this context remain unresolved.

evilcman
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Is this statement true: "If two meromorphic functions have the same poles(all simple) and the same
zeros(all simple), than they are proportional."? If it is true, than why? Thanks for the help...
 
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I believe all meromorphic functions can be written as the ratio of two holomorphic functions. A holomorphic function can be written as a (possibly infinite) product of monomials which are of the form (x-a) where a is a zero of the function. So if f(x) is meromorphic we can write it as g(x)/h(x) where the zeros of g(x) are the zeros of f(x) and the zeros of h(x) are the poles of f(x). If two functions have the same zeros and poles their g(x) and h(x) can only differ by a multiplicative constant.
 
All meromorphic functions can be written as the ratio of two holomorphic functions, that is true.

The second statement is not true. In general a holomorphic function can't be written as a product of monomials.
You will in general also have an exponential in it. And the exponential in it can have a holomorphic function in the
argument: http://en.wikipedia.org/wiki/Weierstrass_factorization_theorem

So is you have the meromorphic functions f1(x)/g1(x) and f2(x)/g2(x), where the fs and gs are holomorphic,
than for example you could have for example f1(x) = exp(h(x)) f2(x) with h(x) some holomorphic function.
 
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What about ez and e2*z? Is that a counterexample?
 

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