On Wed, Apr 8, 2009 at 1:11 PM, David Joyner <wdjoy...@gmail.com> wrote:
>
> On Wed, Apr 8, 2009 at 2:16 PM, Ursula Whitcher
> <urs...@math.washington.edu> wrote:
>>
>> I'd like to know H^3(G,Z) for two particular finite groups, namely L_2
>> (7), also known as the Chevalley group PSL(2,F_7), and M_20, a
>> subgroup of the Mathieu group M_24 which is isomorphic to a semidirect
>> product of (Z/2Z)^4 with the alternating group A_5.
>>
>> Is Sage capable of these computations? If so, how do I express these
>> groups (or how should I start trying to express them)? If not, does
>
> sage: G1 = PSL(2,7)
> sage: MathieuGroup?
>
> explains
>
> """
> The Mathieu group of degree n.
>
> INPUT:
> n -- a positive integer in {9, 10, 11, 12, 21, 22, 23, 24}.
>
> OUTPUT:
> -- the Mathieu group of degree n, as a permutation group
> """
>
> sage: G1.cohomology(3,p=0)
>
> computes what you want f the hap package is loaded
> (using sage -i gap_packages* - see
> http://www.sagemath.org/packages/optional/).
Just for the record it is impossible to install the optional Gap
packages into SAge-3.4, because
the optional Gap spkg that is posted is:
gap_packages-4.4.10_6
and the current version of GAP in Sage is 4.4.12.
We will be downgrading GAP to 4.4.10 (since 4.4.12 is broken on
Itanium) for sage-3.4.1 so this problem will go away soon.
For the record, the following workaround seems to allow the GAP
packages to install:
(1) cd to SAGE_ROOT/local/lib
(2) type "ln -s gap-4.4.12 gap-4.4.10"
(3) Do "./sage -f gap_packages-4.4.10_6"
I've done this for sagenb.org, so if you make an account there and try
this it will work:
sage: G1 = PSL(2,7)
sage: G1.cohomology(3,p=0)
Multiplicative Abelian Group isomorphic to C2
William
>
> For M20, you might want to use GAP directly. See
> http://www.gap-system.org/Packages/hap.html
>
>
>> anyone have a suggestion for a place to look this up, or another
>> computation tool I should use?
>>
>> Thanks!
>> Ursula
>> >
>>
>
> >
>
--
William Stein
Associate Professor of Mathematics
University of Washington
http://wstein.org
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