Laplace transform of Fractional Derivatives (1 Viewer)

AAEldar

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Just some thinking in the shower this morning (I'm a little rusty so forgive me for any errors!).

We have the Riemann-Liouville integral:



So if I take the Laplace transform we get:







I didn't expect that, so it makes me wonder if it's correct? (Then again, after seeing Cauchy weave his magic I shouldn't be too surprised if it is!) Is there a restriction needed on the initial values of the function?
 

seanieg89

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Looks good to me (apart from changing the transformed variable from t to p from the first line to the third line of calculating the Laplace transform). You can even use this as a way of defining fractional differentiation.

It is a common result, we often get these kind of interactions between polynomial multiplication/division and differentiation when it comes to Fourier/Laplace type transforms. (Doing one is equivalent to doing the other to the transformed function.)
 
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AAEldar

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What is the actual meaning behind the lower bound of the fractional derivative?
What we're differentiating with respect to - t in this case.

Looks good to me (apart from changing the transformed variable from t to p from the first line to the third line of calculating the Laplace transform). You can even use this as a way of defining fractional differentiation.

It is a common result, we often get these kind of interactions between polynomial multiplication/division and differentiation when it comes to Fourier/Laplace type transforms. (Doing one is equivalent to doing the other to the transformed function.)
Ah cool, I'm glad it wasn't me overlooking something and it is actually nice! (my bad on the transform variable)
 

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