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Asymptotic behavior of functions, asymptotic series and related topics

6 votes
Accepted

The growth rate of $\left(1+\frac{x}{f(x)}\right)^{f(x)}$

Let's suppose $x/f(x) \to 0$. Then take logarithm. As $x \to \infty$, $$ \log G(x) = f(x) \log\left(1+\frac{x}{f(x)}\right) =f(x)\left(\frac{x}{f(x)}+O\left(\left(\frac{x}{f(x)}\right)^2\right)\righ …
Gerald Edgar's user avatar
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5 votes

Does f(x)~g(x) imply $f(x) \asymp g(x)$?

My version would be this: $f(x) \sim g(x) \Longrightarrow f(x) \asymp g(x)$ is TRUE with the usual definitions, which differ from what we see above. Suppose $f, g$ are positive functions on $\mathbb …
Gerald Edgar's user avatar
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2 votes

textbooks on asymptotic expansions

http://www.amazon.com/Asymptotics-Summability-Monographs-Surveys-Mathematics/dp/1420070312/ Asymptotics and Borel Summability, O. Costin …
4 votes

Inverting an asymptotic series

There is a general technique for doing this, found in expositions dealing with transseries. One example is my own... Transseries for beginners, Real Analysis Exchange 35 (2010) 253--310 see Pro …
Gerald Edgar's user avatar
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45 votes
Accepted

"Closed-form" functions with half-exponential growth

Yes All such compositions are transseries in the sense here: G. A. Edgar, "Transseries for Beginners". Real Analysis Exchange 35 (2010) 253-310 No transseries (of that type) has this intermediate gr …
Gerald Edgar's user avatar
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2 votes

Functions defined as infinite products

For the Maple computation: write $$ 1 - \frac{i}{i^{2} + n} = \frac{(i - \frac{1}{2} - \frac{\sqrt{1 - 4 n}}{2}) (i - \frac{1}{2} + \frac{\sqrt{1 - 4 n}}{2})}{(i + \sqrt{-n}) (i - \sqrt{-n})} $$ then …
Gerald Edgar's user avatar
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0 votes

Natural candidates for sub-half-exponential which limit to half-exponential function from below

Not an answer Merely remarks. Let me use superscript $[k]$ for $k$-fold composition. $\log^{[3]} n$ means $\log\log\log n$. As I remarked on the other question, for fixed $a$ and $n$, the value $f(k, …
Gerald Edgar's user avatar
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4 votes

Can one show combinatorially how $\operatorname{lcm}(1, \dotsc, n)$ grows?

Its asymptotics are found in Chapter XXII, which leads up to the proof of the prime number theorem. Write $\psi(x) = \log U(x)$. …
Gerald Edgar's user avatar
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