Sunday, 29 November 2015

calculus - Interchanging Inverse Laplace Transform

I have a function f(|k|,s,θ) for which I am interested in its inverse Laplace transform. I am also interested in the function's mean value for constant |k|, but technically I need to inverse Laplace transform first. I was wondering about the interchangeability of the inverse transform and the mean; that is, does:



12π2π0L1{f(|k|,s,θ)}dθ=L1{12π2π0f(|k|,s,θ)dθ}
The inverse Laplace transform is w.r.t. s.



I could think of a few reasons why it may not hold; for example, would it hold if doing the mean integration first affects the poles of s (if that could happen)?




Please forgive my lack of knowledge in math, I do not know much measure theory and am not sure of the formality of interchanging these two operators. Any help is greatly appreciated!



EDIT: The actual function looks like:



f(|k|,s,θ)=λ2(D|k|2+2λ1+s)+λ1(ikv+λ1+s)+λ22(λ1+λ2)((D|k|2+s)(ikv+λ1+s)+λ2(s+ikv))
All variables are real and positive except for s, of course. θ is the angle between v and k. Carrying out the mean integration first gives:
f(|k|,s)=λ1(λ1+λ2)(D|k|2+λ2+s)
which makes it easy to then find the inverse Laplace transform. Not sure if this is at all helpful.

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