Exploring Fourier Transforms and Integrability for Different Functions

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Discussion Overview

The discussion centers on the conditions under which the function f(x) = (1 + |x|)^{-a} can be considered the Fourier transform of an integrable function on R, particularly focusing on the parameter a and its implications for integrability. Participants also inquire about the behavior of the function f(x) = 1/(log(|x|^2 + 2)) in this context.

Discussion Character

  • Exploratory, Homework-related, Technical explanation

Main Points Raised

  • One participant asserts that for f(x) = (1 + |x|)^{-a} to be the Fourier transform of an integrable function, the parameter a must be greater than 1 to ensure convergence of the integral during the inverse transform.
  • Another participant questions the behavior of the function when 0 < a <= 1, suggesting that it may not satisfy the integrability condition.
  • A third participant expresses uncertainty about formalizing their argument regarding the conditions for integrability and admits to being unclear about the implications of the function f(x) = 1/(log(|x|^2 + 2)).

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of the parameter a for integrability, and there is uncertainty regarding the third function mentioned. The discussion remains unresolved.

Contextual Notes

Limitations include the lack of formal proofs or detailed mathematical steps to support claims about integrability and convergence.

shoplifter
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prove that f(x) = (1 + |x|)^{-a} is the Fourier transform of some integrable function on R, when a > 1. what happens when 0 < a <= 1? how about the function f(x) = 1/(log(|x|^2 + 2))?
 
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Is this homework? If so, what have you done so far?
 
yes, and i realize that we want the integral to converge when we take the inverse transform. so in order to do that, I'm guessing the denominator has to have a power > 1, which is why we have that condition on a. so it will fail the second time, i guess. but i can't formalize my argument (and I'm clueless about the third one).

sry :(
 
any help please? :(
 

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