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Automorphisms of finite projective planes

Please consult the handout about Finite Projective Planes.

Conjecture 3.4   Not every finite group is isomorphic to the group of automorphisms (collineations) of a finite projective plane. In fact, not every finite group is isomorphic even to a subgroup of the automorphism group of a finite projective plane. $ A_6$ appears to be a candidate; $ A_{100}$ looks like an easier one to rule out as a subgroup.


\begin{exercise}
% latex2html id marker 862
If $P$\ is a finite projective plane...
...$Q$\ is
a subplane, then the order of $Q$\ is at most $\sqrt{n}$.
\end{exercise}


\begin{exercise}
% latex2html id marker 864
Let $P$\ be a finite projective plan...
... number
of times you can iteratively take the square root of $n$.
\end{exercise}


\begin{exercise}
% latex2html id marker 867If $P$\ is a finite Galois plane of...
...then $\vert\mathop{\rm Aut}({\mathbb{F}}_q)\vert=r
\le \log_2 q$.
\end{exercise}

Conjecture 3.5   If $ P$ is a projective plane of order $ n$, then % latex2html id marker 2044
$ \vert\mathop{\rm Aut}(P)\vert\le n^C$ for some constant $ C$. Perhaps, % latex2html id marker 2048
$ \vert\mathop{\rm Aut}(P)\vert\le n^{8+o(1)}$.



Varsha Dani 2003-08-04