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gap-packages / primgrp

GAP Primitive Groups Library
https://gap-packages.github.io/primgrp/
GNU General Public License v2.0
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wrong name for two primitive groups #17

Closed ThomasBreuer closed 6 years ago

ThomasBreuer commented 6 years ago

The first two groups in the following list have apparently a wrong name.

gap> AllPrimitiveGroups( Size, 17971200, IsSimpleGroup, true );
#W  AllPrimitiveGroups: Degree restricted to [ 2 .. 4095 ]
[ 2F(4, 2), 2F(4, 2), 2F(4, 2)', 
  <permutation group of size 17971200 with 2 generators> ]
gap> List( last, NrMovedPoints );
[ 1600, 1755, 2304, 2925 ]
fingolfin commented 6 years ago

Indeed, these three groups are all isomorphic copies of the Tits group. There seems to be a naming clash here:

In data/gps22.g, the groups are called 2F(4, 2)' (the third group in Thomas' list), and 2F(4, 2) (the overgroup of size 35942400).

In data/gps17.g, these twp groups are called 2F(4, 2) respectively 2F(4, 2):2.

In data/gps15.g, we find again 2F(4, 2) as name for the Tits group.

I agree with Thomas that the simple groups should be called 2F(4, 2)', which also agrees with the output of IsomorphismTypeInfoFiniteSimpleGroup. I'll submit a pull request for this.

olexandr-konovalov commented 6 years ago

Thank you @ThomasBreuer. I've made a new release, which hopefully be included in GAP 4.10.0 distribution.