Wednesday, 14 June 2017

real analysis - Turning a continuous everywhere differentiable nowhere function into a smooth function by infinitely many times definite integration?

Let W(x) be a real-vlued function defined on a (possibly infinite) interval TR containing 0 that is continuous everywhere differentiable nowhere on T.



Define the sequence of function fn:TR as follows:
f0(x)W(x)

and fn(x)x0fn1(u)du
for n=1,2,3,4,5,... .



Then it follows the fact that fn is differentiable exactly n-times everywhere on T.



Question:



Does there exist such W(x) and T so that the sequence of function fn on T "converges" to a limit function f on T with f being infinitely many times differentiable (i.e., smooth) on T?

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