Square integrable/vanish at infinity?

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The discussion centers on the properties of square integrable functions, specifically differentiable complex-valued functions on R. It establishes that a function f being square integrable does not necessitate that lim x-> +/- infinity of f(x) approaches zero, illustrated by the counterexample f(x) = x^2 exp(-x^8 sin^2(20x)). Furthermore, the inquiry is raised whether requiring the derivative of f to also be square integrable is sufficient to ensure that f(x) approaches zero at infinity.

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kharranger
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Let f be a differentiable complex valued function on R. If f is square integrable, then it is not the case that f(x) must approach zero at infinity. counterexample: f(x)=x^2 exp(-x^8 sin^2(20x)).
If I also require that the derivative of f be square integrable, is that enough to guarantee that lim x-> +/- infinity of f(x) is zero?
Thanks,

KH
 
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i think square integrable means the quare of the aBSOLUTE VAlue is finite.
 

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