Does the Convolution Theorem Hold for Fourier Transforms Using Omega?

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The discussion centers on the applicability of the convolution theorem for Fourier transforms when using different definitions of the Fourier transform, specifically regarding angular frequency (omega) versus ordinary frequency (xi). It is established that the convolution theorem holds for all variants of the Fourier and Laplace transforms, regardless of the normalization constants or the presence of 2π in the exponent. Consistency in the application of these definitions is crucial for the theorem to remain valid. A reference to Wikipedia indicates that while the theorem holds, an additional multiplication by √2π is required when using the angular frequency definition with a specific normalization constant. Overall, the convolution theorem's validity is affirmed across different formulations as long as proper adjustments are made.
dimension10
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I have a question on the Convolution theorem for Fourier Transforms. The convolution theorem states that

\mathscr{F}\{f(t) g(t)\}=\mathcal{F}\{f(t)g(t)\}=\mathcal{F}\{f(t)\}\ast \mathcal{F}\{g(t)\}-\mathscr{F}\{f(t)\} \ast \mathscr{F}\{g(t)\}

\mathscr{F}\{f(t) \ast g(t)\}=\mathcal{F}\{f(t)\ast g(t)\}=\mathcal{F}\{f(t)\}\mathcal{F}\{g(t)\}= \mathscr{F}\{f(t)\}\mathscr{F}\{g(t)\}

and the same for the Laplace Transform.

However, my sources use the definition of the Fourier Transform as

\mathscr{F}\{f(t)\}=\mathcal{F}\{f(t)\}=\int_{-\infty}^{\infty}{e}^{-2i\pi\xi t}f(t) \mbox{d}t

But my question is that if I were to use the definition,\mathscr{F}\{f(t)\} = \mathcal{F}\{f(t)\}=\frac{1}{ \sqrt{2\pi} }\int_{-\infty}^{\infty}{e}^{-i\omega t}f(t) \mbox{d}t

then will the convolution theorem for Fourier transforms still hold? There is one article that states that it does hold. However, when I checked Wikipedia, they say that the convolution theorem for Fourier transforms does not hold for the definition which uses angular frequency instead of ordinary frequency.

So, does the Convolution theorem for Fourier Transforms still hold for the definition involving omega instead of xi.
 
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Hi dimension10! :smile:

Yes, the convolution theorem holds for all variants of the Fourier transform and the Laplace transform.

It is an arbitrary choice whether you include 2pi in the exponent or not.
It is also an arbitrary choice where you put the normalization constant, which can be in the Fourier transform, the Inverse Fourier transform, or in both.
As long as you're consistent of course.
 
I like Serena said:
Hi dimension10! :smile:

Yes, the convolution theorem holds for all variants of the Fourier transform and the Laplace transform.

It is an arbitrary choice whether you include 2pi in the exponent or not.
It is also an arbitrary choice where you put the normalization constant, which can be in the Fourier transform, the Inverse Fourier transform, or in both.
As long as you're consistent of course.

Ok thanks a lot.
 
I was curious where you may have found that the convolution theory would not hold, so I tried to look it up in wikipedia.

What I found is this:
http://en.wikipedia.org/wiki/Fourier_transform#Functional_relationships
In the table, you can see that the convolution theorem holds, but in the case of angular frequency with a normalization constant of 1 \over\sqrt{2\pi} in the Fourier transform, you also need to multiply by \sqrt{2\pi} for the convolution theorem to hold.
 
I like Serena said:
I was curious where you may have found that the convolution theory would not hold, so I tried to look it up in wikipedia.

What I found is this:
http://en.wikipedia.org/wiki/Fourier_transform#Functional_relationships
In the table, you can see that the convolution theorem holds, but in the case of angular frequency with a normalization constant of 1 \over\sqrt{2\pi} in the Fourier transform, you also need to multiply by \sqrt{2\pi} for the convolution theorem to hold.

Thanks.
 

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