From: David Harden on
Suppose G is a group and it contains subgroups isomorphic to A_8 and
PSL(3,F_4). How small can G be?
If I knew nothing about this problem, I would say we can take |G| <=
20160^2 = 406425600.
However, I do know something about it: we can take |G| <= 10200960
because the Mathieu group M_23 works. But that is as far as I can go.
From: Derek Holt on
On 5 June, 19:05, David Harden <roddl...(a)mit.edu> wrote:
> Suppose G is a group and it contains subgroups isomorphic to A_8 and
> PSL(3,F_4). How small can G be?
> If I knew nothing about this problem, I would say we can take |G| <=
> 20160^2 = 406425600.
> However, I do know something about it: we can take |G| <= 10200960
> because the Mathieu group M_23 works. But that is as far as I can go.

A_8 and PSL(3,4) must both be subgroups of some composition factor of
G. If they are subgroups of different composition factors then |G|
>=20160^2. It can be checked, by using the ATLAS for example, that
M_23 is the smallest simple group that contains them both as
subgroups, so M_23 is the (unique) smallest group containing them
both. The Higman-Sims group HS of order 44352000 is the next smallest
example.

Derek Holt.