[GAP Forum] list simple groups, again

[Dima Pasechnik]

On Wed, Dec 18, 2019 at 11:21:11PM +0000, Hulpke,Alexander wrote:
> Dear Forum, Dear Keith,
> 
> > Is there something wrong with my installation?
> No. Both issues are in the released code.
> 
> You encounter two different issues where particular cases have not yet been implemented. As they occur only for comparatively large groups I felt the functionality for simple groups was valuable as-is without having to wait for these cases to be sorted out. Both have to do with triality automorphisms, and would be somewhat fiddly to get right.
> (If anyone has code or ready descriptions for these cases, I would be happy to include it for future releases.)
> 
> > GRP[208]:=[208,65784756654489600,"O",[9,3]]
> > Error, mixed triality not yet done at
> > /home/dennis/GAP4.10.1/gap-4.10.1/grp/simple.gi:859 called from
> > EFactors( Gcd( 2, (par[2] - 1) ) ^ 2, expo, 6 ) at
> > /home/dennis/GAP4.10.1/gap-4.10.1/grp/simple.gi:1047 called from
> > DataAboutSimpleGroup( id ) at
> 
> DataAboutSimpleGroups calculates (beyond what IsomorphismTypeInfoFiniteSimpleGroup does) — among other things — the structure of the outer automorphism group.
> For type D4 this involves also the triality automorphism, and the current code does not yet consider its interaction with field automorphisms — thus the error message.
> 
> > GRP[211]:=[211,67671071404425216,"U",[3,127]]
> > Error, Can't do yet at
> > /home/dennis/GAP4.10.1/gap-4.10.1/grp/simple.gi:577 called from
> > CallFuncList( SimpleGroup, b ) at
> 
> This would be the Chevalley group of type 3D4(4). The simple groups code does not construct groups as Chevalley groups, but as classical groups of from existing libraries. I am not aware of an existing library that contains a representation of 3D4(4).
> (The same holds for any larger fields and certain other large exceptional groups).

Does anyone has GAP code to build a representation of 3D4(q) (for any
q=p^k) ?
We'd like to have it for a project where we build a library of
distance-regular graphs.


Thanks
Dima

> 
> Regards,
> 
>   Alexander Hulpke
> 
> 
> > /home/dennis/GAP4.10.1/gap-4.10.1/grp/simple.gi:696 called from
> > 0 = cnt mod len at SimpleGroupList.gap:83 called from
> > <function "ListSimpleShortNoL2">( <arguments> )
> > called from read-eval loop at *stdin*:5
> > you can 'quit;' to quit to outer loop, or
> > you can 'return;' to continue
> > brk> return;
> > Error, Variable: 'g' must have an assigned value in
> >  if s <> fail and not HasName( g ) then
> >    SetName( g, s );
> > fi; at /home/dennis/GAP4.10.1/gap-4.10.1/grp/simple.gi:629 called from 
> > CallFuncList( SimpleGroup, b ) at
> > /home/dennis/GAP4.10.1/gap-4.10.1/grp/simple.gi:696 called from
> > 0 = cnt mod len at SimpleGroupList.gap:83 called from
> > <function "ListSimpleShortNoL2">( <arguments> )
> > called from read-eval loop at *stdin*:5
> > you can 'return;' after assigning a value
> > brk> 
> > 
> > 
> > 
> > 
> > 
> > Ok, I tried the NOSL2 option, and ran into another problem.
> > 
> > 
> > Keith
> > 
> > 
> > 
> > _______________________________________________
> > Forum mailing list
> > Forum at gap-system.org
> > https://mail.gap-system.org/mailman/listinfo/forum
> 
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