What is the upper bound for the given function f(t,p)?

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The discussion centers on determining the upper bound for the function f(t,p) defined as f(t,p)=∑_p (p(1-p)/t^5)[p^4(9t^4-81t^3+225t^2-274t+120)+p^3(-12t^4+129t^3-400t^2+524t-240)+p^2(4t^4-59t^3+216t^2-311t+150)+p(7t^3-36t^2+59t-30)+(t-1)^2]. The conclusion drawn is that the function g(t) can be approximated as g(t)∼1/t, but no better bound can be established without additional constraints on p relative to t. The worst-case scenario leads to f(t,1)=O(t^{-1}), indicating that only a better constant can be derived.

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phonic
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Dear members,

I try to find the upper bound of the following function. Can anybody gives a hint? Thanks!

[tex] f(t,p)=\sum_p \frac{p(1-p)}{t^5}[p^4(9t^4-81t^3+225t^2-274t+120)+p^3(-12t^4+129t^3-400t^2+524t-240)+[/tex]
[tex] \mbox{\hspace{2cm}}p^2(4t^4-59t^3+ 216t^2-311t+150)+p(7t^3-36t^2+59t-30)+(t-1)^2][/tex]
where
[tex] t=1,2,3,..[/tex]
[tex] \sum_p p = 1[/tex]

The problem is to find the function g(t) that
[tex] f(t,p) \leq g(t)[/tex]
It seems that
[tex] g(t)\sim 1/t[/tex]
Is it possible to find a better bound?
 
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No. Not as long as no additional conditions on ##p## in dependency of ##t## are given. You can assume the worst case of ##\sum_p=p=1## and get ##f(t,1)=O(t^{-1})## so all you can do is finding a better constant.
 

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