A question on sequence of functions.

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The discussion revolves around the existence of a continuous, non-periodic function g: R -> R such that for any sequence of real numbers {a_k}, the functions g_k(x) = g(x + a_k) have a uniformly converging subsequence on R. Participants explore examples like g(x) = sin(e^x) and g(x) = exp(-x^2), debating their properties and the implications of the Arzelà-Ascoli theorem. The consensus suggests that while finding such a function is challenging, examples like sin(x) + cos(πx) and 'almost periodic' functions may satisfy the criteria. The conversation highlights the nuances of periodicity and equicontinuity in the context of uniform convergence. Ultimately, the group concludes that while difficult, the existence of such a function is plausible.
  • #31
ok, what about the question with which iv'e opened the thread?
 
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  • #32
loop quantum gravity said:
i thought a periodic function has a small period which is non zero, here clearly there isn't such period.
anyway, if this is considered a periodic function then back to the original question is there such a function which is not periodic?

I think NateTG's example sin(x)+cos(pi*x) is an excellent example of a function that statisfies your requirements (as are 'almost periodic' functions in general). How many times has that been stated on this thread? Can you prove it?
 
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  • #33
i think by arzela ascoli theorem i only need to show that it's uniformly bounded (obviously it is by: 2. and that this sequence of functions is equicontinuous, which is also bacause of the first derivative is uniformly bounded so it's equicontinuous.

ok, thanks Dick,Nate and also Matt, i appreciate your help on this question.
 

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