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Does someone know whether the order of the automorphism group of a general p-group of order $p^n$ is bounded from above by $(p^n)^2 $? (Every element can possibly be transferred to one of other $p^n$ elements)...

If this fact is incorrect, is it possible to deduce a bound on the order of such an automorphism group if our p-group is finitely generated?

Thanks in advance

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See this previous question: mathoverflow.net/questions/68109/…. The order of the automorphism group of a group of order $p^n$ divides $(p^n-1)(p^n-p)\cdots(p^n-p^{n-1})$, and the bound is sharp, achieved by the elementary abelian $p$-group of rank $n$. –  Arturo Magidin May 30 '12 at 16:12
    
Thanks ! !!!!!!!!!!!!! –  jason mfash May 30 '12 at 16:33
    
So, is it true that the order of the aut group if $O(p^{2n})$? –  jason mfash May 30 '12 at 16:38
    
The bound Arturo gave is not $O(p^{2n})$ but $O(p^{n^2})$. –  Andreas Blass May 30 '12 at 17:12
    
Great ! Thanks ! –  jason mfash May 30 '12 at 17:31

1 Answer 1

up vote 2 down vote accepted

For a specific counterexample to the fact that $p^{2n}$ is not an upper bound, take the elementary abelian group of order $p^3$. It has automorphism group of order $(p^3-1)(p^3-p)(p^3-p^2)$ (pick a basis; the first basis vector can go to any nonzero vector; the second to any vector not in the linear span of the first; the third to any vector not in the linear span of the first two images). For $p=3$, this gives $11232$ automorphisms, larger than $(3^3)^2 = 729$.

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So, is it true that the order of the aut group if $O(p^{2n})$? –  jason mfash May 30 '12 at 16:39

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