Analytic Functions: Is f(z) an Element of the Algebra of Polynominals?

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Discussion Overview

The discussion revolves around the nature of analytic functions and their relationship to polynomials, particularly whether an analytic function that can be locally expressed as a power series qualifies as an element of the algebra of polynomials in z. The conversation touches on theoretical aspects and implications for invariant theory and statistical physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that an analytic function f(z) can be considered an element of the algebra of polynomials in z if it can be locally expanded in a power series, provided that the power series is finite.
  • Others argue that by definition, a polynomial must have a finite highest power, which implies that infinite power series do not qualify as polynomials.
  • A later reply expresses interest in extending the concept of polynomials to analytic functions, particularly in the context of invariant theory and statistical physics, and seeks insights on how the "pull back" mechanism might apply to analytic functions.

Areas of Agreement / Disagreement

Participants generally agree on the definition of polynomials as functions with a finite highest power. However, the broader question of whether analytic functions can be classified similarly remains unresolved, with differing views on the implications of power series expansions.

Contextual Notes

The discussion does not resolve the conditions under which an analytic function may or may not be considered a polynomial, nor does it clarify the assumptions regarding the nature of the power series involved.

timb00
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Hey everybody,

I have a short question. Suppose you have an analytic function f(z) such that you can, at least locally, expand it in a power series. Is this function then (locally) an element of the algebra of polynominals in z?

I hope I formulate the question in the right way.

Best wishes, Timb00
 
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timb00 said:
Hey everybody,

I have a short question. Suppose you have an analytic function f(z) such that you can, at least locally, expand it in a power series. Is this function then (locally) an element of the algebra of polynominals in z?

I hope I formulate the question in the right way.

Best wishes, Timb00



Only if the power series (locally) is finite.

DonAntonio
 
Second DonAntonio. A "polynomial", by definition, has a (finite) highest power.
 
Thank you for your fast answers. They have confirmed my expectancy. I ask this question because I am concerned with invariant theory and statistical physics. I learned that every polynominal function that is invariant under the action of a Lie group is a pull back of a function on some matrix space depending on the Lie group. Due to this observation I ask my self how this is extended to the space of analytic functions.

Maybe some one of you has an Idea how to extend this "pull back" mechanism to analytic functions.

Timb00
 

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