Fourier transforms in Hilbert Space

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SUMMARY

The discussion centers on the application of Fourier transforms within Hilbert spaces, specifically addressing the representation of functions in classical physics using Fourier components. The key equation discussed is F(sin(nx)) <--> iπ(δ(ω+n) - δ(ω-n), highlighting the role of Dirac delta functions in this context. The participant, Fritz, questions the compliance of delta functions with Hilbert space rules, noting their nature as distributions rather than functions. The conversation concludes with a reference to rigged Hilbert spaces, which provides clarity on the topic.

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  • Understanding of Fourier transforms and their mathematical representation.
  • Familiarity with Hilbert spaces and their properties.
  • Knowledge of Dirac delta functions and their role in distributions.
  • Concept of rigged Hilbert spaces and their significance in functional analysis.
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  • Learn about the implications of distributions in functional analysis.
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Mathematicians, physicists, and students of functional analysis who are interested in the theoretical foundations of Fourier transforms and their applications in Hilbert spaces.

sonnichs
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I am thinking about the simple Fourier transform: F( sin(nx) ) <--> iπ( δ(ω+n) - δ(ω-n) }
I believe I can represent most of the functions in classical physics, f(x), in a Hilbert space by expressing them using their Fourier components as a basis.
This leads to a spectrum which is represented by the dirac-delta functions. Each axis in the space represents "n" for the delta and its length is the multiplier of the Fourier element of that function.

I can define a reciprocal space for these delta functions, each axis for δ(ω+n) being sin(nx).

I thought that such a space would also exist in the same Hilbert space--but am I incorrect? The delta function does not seem to comply with the rules of elements in a Hilbert space--it is a distribution--not a function?

thanks-Fritz
 
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sonnichs said:
I thought that such a space would also exist in the same Hilbert space--but am I incorrect? The delta function does not seem to comply with the rules of elements in a Hilbert space--it is a distribution--not a function?
See https://en.wikipedia.org/wiki/Rigged_Hilbert_space.
 
Thank you Gavran. This explains my premise. -FS
 

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